What an image depicts depends on what an image means

COGNITIVE PSYCHOLOGY 24, 145-174 (1992)

What an Image Depicts Depends on What an Image Means

DEBORAH CHAMBERS

North Dakota State University

AND

DANIEL REISBERG

Reed College

Previous research has shown that subjects visually imaging the classical ambiguous figures have great difficulty in reconstruing these images. To explain this finding, we propose that subjects’ construal of their image strongly influences what is depicted in the image, leading to the inclusion of some aspects of an imaged figure and the exclusion of others. Thus, images of (supposedly) ambiguous figures may literally omit information necessary for the reconstrual. To test this claim, we asked subjects to form an image of the duck/rabbit figure, and then to compare their image to drawings that departed slightly from the original figure. We hypothesized that subjects would have a clear image of the side of the figure they understood as the “face” (the left side if the image is understood as a duck, the right side for the rabbit). Conversely, subjects would have only a vague image of the “back” of the head. Consequently, in comparing their image to test stimuli, subjects should be able to detect variations in the contour of the “face,” but not in the contour of the “back” of the animal’s head. These predictions were con- firmed, strongly suggesting that the construal of an image does dictate what is depicted within the image. o lw! Academic PXSS, hc.

Previous research has shown that subjects have great difficulty in reinterpreting their own mental images (Chambers & Reisberg, 1985). In these prior studies, subjects attempted to reinterpret images of the duck/ rabbit, the Necker Cube, or the Schroder Staircase (Fig. 1). The subjects were unfamiliar with these ambiguous figures, allowing us to ask whether they could discover the reconstrual of the figure from imagery. Subjects were shown the figures briefly, then imaged the forms and examined the image seeking an alternate construal. Subjects had previously received

We thank Arien Mack and David Smith for their discussion throughout the course of this project. Many of the experiments described here were presented to the New School for Social Research as the first author’s Doctoral Thesis. Experiments 2, 3, and 4 were presented at the Annual Meetings of the Psychonomic Society (1988). Reprint requests should be sent to Daniel Reisberg, Psychology Department, Reed College, Portland, OR 97202.

145 OOlO-0285/92 $7.50 Copyright Q 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.

146 CHAMBERS AND REISBERG

a b c FIG. 1. Test stimuli employed by Chambers and Reisberg (1985). (a) The Jastrow duck/

rabbit. (b) The Schroder Staircase. (c) The Necker Cube.

practice with ambiguous figures other than the test stimulus to ensure that they understood the task. In addition, to aid subjects in reconstruing the image, they were given a series of prompts urging them (among other steps) to shift their gaze from one corner of the figure to another.

Despite training and hints, 100% of the subjects failed to find the alternative construal of their image. In marked contrast, virtually all of the subjects were able, a moment later, to draw the figure they had been imaging, and then to reconstrue their own drawings. This indicates that they had adequately encoded the figure and that they understood the reconstrual task.

Similar results have been obtained with auditory imagery (e.g., Reis- berg, Smith, Baxter, & Sonenshine, 1989). As their ambiguous inputs, Reisberg et al. exploited the fact that certain words, if repeated over and over, yield a soundstream compatible with more than one segmentation (Warren, 1961, 1982; Warren & Gregory, 1958). For example, rapid repetitions of the word “life” produce a physical soundstream fully compatible with segmentations appropriate to repetitions of “life” or of “fly.” These repetitions are usually perceived first as one of these words, then the other, then the first, changing in phenomenal form just as the Necker Cube or duck/rabbit do. With imaged repetitions, however, these transformations are not detected, even when subjects are explicitly instructed to search for a reconstrual of the image. (More precisely, these auditory images do not support reconstrual if subjects are blocked from subvocalization. If subvocalization is allowed, subjects do seem able to reinterpret this “enacted” image. See Smith, Reisberg, & Wilson, 1991, for discussion.) Thus auditory images (without subvocalization) seem no more ambiguous than visual images.

In all these “ambiguous image” studies, subjects fail to make discoveries from their images, even though discoveries are easily made when the appropriate figures are perceptually available. In seeming contrast, though, the literature contains ample evidence that we are able to learn or make discoveries from images (Finke, 1989; Miller, 1986; Shepard & Cooper, 1982). In fact, Finke, Pinker, and Farah (1989) presented data

IMAGES ARE NOT EVERYWHERE DENSE 147

that they considered an explicit challenge to the Chambers and Reisberg (1985) findings just described. Their subjects were instructed, for example, to imagine a “D,” then to imagine this shape rotated counterclockwise 90”, and finally to place a “J” in the middle of its spine. Subjects often reported that the resulting image resembled an umbrella. These results (and many others) make it plain that subjects can discover unan- ticipated forms in mental imagery.

Why, therefore, did the Chambers and Reisberg (1985) subjects fail to learn from their images, fail to discover the duck in the rabbit image (and vice versa)? We have argued elsewhere (Reisberg & Chambers, 1991) that learning from imagery is constrained in important ways. Our suggestion is that discoveries from images will occur only if the “target” form is compatible with the imaged geometry and with certain specifications about that geometry. These specifications include an identification of the figure’s top, its figure/ground organization, its parsing, and so on. Classic perception data make it plain that these specifications strongly influence what is learned from or remembered about, perceived stimuli (Rock, 1973; Goldmeier, 1937/1972), and Reisberg and Chambers (1991) report comparable influence of these specifications in imagery. For example, subjects imaging Fig. 2 were consistently unable to discover the identity of this figure, even when they imagined it rotated 90” clockwise (placing the form in its canonical orientation). With this rotation, subjects were imaging a form with the same geometry as Texas, but with a different specification of “top.” Thanks to this specification, the image did not call Texas to mind. However, if subjects were directly instructed to change

FIG. 2. Texas rotated 90” counterclockwise After Reisberg and Chambers, 1991.


their specification of the form’s top (i.e., if they were instructed to consider the left side to be the top), then many were able to identify Texas from their images. Thus, it seems that an image can depict a very familiar shape without evoking that shape (i.e., without that shape being recog- nized). In this regard, images are like percepts, with similarity in both cases governed not by the geometrical shape alone but also by how the imager, or the perceiver, understands that shape.

But this still leaves us with a puzzle. The duck and the rabbit of Jas- trow’s figure share both an overall shape, and also the same top, and the same figure-ground organization. On the Reisberg and Chambers (1991) account just described, these shared properties should lead one image (e.g., the duck) to evoke another (e.g., the rabbit). However, subjects universally failed to find a duck in their rabbit image (and vice versa). Hence, the Chambers and Reisberg (1985) result seems inconsistent with the Reisberg and Chambers (1991) proposal.

To resolve this puzzle, we need to enlarge the Reisberg and Chambers (1991) proposal. The heart of the Reisberg and Chambers (1991) proposal is that images are (obligatorily) accompanied by an understanding, with this understanding composed of a small number of perceptual specitica- tions. We now propose that subjects’ understanding of an image also shapes the image in an important way. As a premise, we assume that subjects do not include all aspects of a depicted stimulus within their images. As we will discuss below, both introspective reports and experimental data support this assumption. Given this, we propose that the pattern of what is included and excluded from an image is heavily shaped by how subjects understand the imaged form. It is possible then that subjects who construed their image as a duck may include aspects of the form that are critical to the duck construal, but not include aspects critical to a rabbit construal. As a result, information needed for reconstruing the image may literally have been unavailable.

It seems uncontroversial that verbal or pruposirional descriptions are in many ways selective. One can mention someone’s hat without describing the color of her hair; one can describe an object’s color without mention- ing how far away the object is, and so on. But depictions seem different in these regards: A picture showing an object’s color must show the object as viewed from a specific distance. A picture of someone’s hat will either include the hair, or will include something that obscures view of the hair. Indeed, this “obligatory inclusion” of certain information seems part of what defines a depictive representation, as opposed to a description (e.g., Dennett, 1981; Kosslyn, 1983).

In many regards, mental images clearly function as depictions, not descriptions (e.g., Kosslyn, 1983). That is, images preserve spatial layout, they seem obligatorily to represent a scene as “viewed” from a certain


perspective and distance, and so on. At the same time, though, images, like descriptions, can be quite selective. Introspective evidence indicates that images rarely include all aspects of the object they were intended to depict (James, 1890; Koffka, 1912, cited in Arnheim, 1969; Titchener, 1926). More recently, Slee (1980) has exploited this as a measure of image vividness, asking to what extent an individual’s images include aspects that would be critical to a picture of an object. For example, if a subject images a cup placed on a table, does the image include the shape of the table, or its color? Slee reports that subjects differ enormously in the level of such detail reported as part of their images. In the same spirit, Dennett (1981) has argued that this “noncommittal” aspect of images is a factor that clearly distinguishes mental representations (e.g., images and percepts) from physical representations (e.g., pictures).

The considerations just mentioned rest largely on introspections about what images do or do not include. There is, however, experimental evidence that makes the same general point. Based on studies of performance with imagery tasks, Kosslyn has argued that images begin to fade as soon as they are constructed, but that one can maintain the image by a refreshing process linked to mental scanning or attention (Kosslyn, 1980, 1983; also see Hampson & Morris, 1978). Crucial for our purposes, the resources needed for this refreshing process are limited and so if the image is large, or complex, only some parts of the image can be represented at one time. Again, this leads to the claim that images do not include all aspects of the form they were meant to represent.

This evidence converges with findings from perception indicating that percepts, like images, are not everywhere dense (Hochberg, 1982; Navon, 1977; Palmer, 1980; Rock, Halper, & Clayton, 1972). That is, percepts clearly specify some aspects of a form, but leave other aspects vague and indeterminate. For example, Rock et al. (1972) showed subjects a complex nonsense form for a few seconds, then removed the form and immediately presented two alternatives for a forced-choice recognition task (Fig. 3a). The two alternatives shared the global shape of the original figure and differed only in the nuance of one section of the contour. Recognition performance was at chance levels, despite the lengthy study time and the zero retention interval. However, when the differing segments of the figures were isolated so that each was perceived as a figure (rather than as details of a larger shape), performance was quite good, with subjects easily recognizing the previously viewed form (Fig. 3b).

Rock et al. (1972) account for these results by arguing that the internal description which constitutes a form percept need not include all details of the stimulus input. That is, “when a given region of a form is an inconsequential part of the whole, something is lacking in the perception


a

b FIG. 3. After Rock, Halper, and Clayton (1972). See text for explanation.

ofit. . . But when the physical region of the contour constitutes the form there is no difficulty in perceiving and storing all of its nuances” (Rock, 1983, pg. 55).

From a somewhat different perspective, Hochberg (1981, 1982) similarly concludes that the “schematic map,” which in his view constitutes a form percept, is not “everywhere dense.” In several experiments, Hochberg (Hochberg, 1981, 1982; Hochberg & Peterson, 1987) has dem- onstrated that the percept is dominated by “local cues,” within fovea1 view, and includes only a vague impression of information elsewhere in the form. Again, this argues that the percept does not include all of the details that are visible within a stimulus, but is selective in important ways.

Thus mental representations such as images or percepts are not literal or complete transcriptions of an object, but are instead selective: clear about some aspects of a scene or object, vague and indeterminate about others. But what guides or shapes the selection? Several factors are likely to be relevant, including how quickly one can refresh the image relative to the speed of fading; how attention and/or eye movements are deployed, the specific task (cf. Kosslyn, 1980, 1983), general visual factors such as the size of fovea1 view (Hochberg, 1982), and perhaps general knowledge about the scene (cf. Friedman, 1979). We will argue, in addition, that the specific meaning of the image (or percept) also plays a pivotal role.

Evidence for this last claim comes from perceptual data of Tsal and Kolbet (1985). Tsal and Kolbet found that, when subjects construe the


duck/rabbit figure as a duck, attention (measured by increased sensitivity to a probe) is deployed to the side of the figure depicting the face of the duck. (The results are appropriately reversed for subjects construing the form as a rabbit.) Thus, subjects’ construal of the form clearly biases attention to a specific local area.

In this paper, we seek to extend the Tsal and Kolbet (1985) claim to visual imagery. We propose that, in imagery as in perception, the specific meaning of an image guides how attention is deployed across the image. Thus, which aspects of an image will be clear and which will be vague will also depend on the specific meaning of the image. In this way, the meaning of an image does not merely accompany the depicted geometry; instead the meaning of an image literally shapes the depiction. We will explore this claim further in the General Discussion. First, we will describe the evidence supporting this claim.

GENERAL EXPERIMENTAL METHOD

In the experiments reported here we employed a test similar to that used by Rock et al. (1972). That is, we examined the content of subjects’ images by asking subjects which of two shapes (pictorially presented) better resembled the imaged form. As in Rock et al.‘s (1972) studies, the test shapes differed only in the nuances of one section of the figure.

In each experiment, subjects were asked to create an image of the duck or the rabbit; then after a brief inspection period, subjects were presented with a test pair and asked which of these “matched” their image (i.e., matched the figure they had originally seen). The test pair always included the original figure (Fig. 4a) and one other-either a stimulus that was altered on the “duck’s bill” (Fig. 4b) or one altered on the “rabbit’s nose” (Fig. 4~).

Our hypothesis is that imagery subjects, like Tsal and Kolbet’s (1985) perception subjects, attend to the area of their images depicting (what they consider to be) the face of the imaged animal. Consequently, subjects are likely to maintain this area of their images and to allow other areas to fade. (For further discussion of the link between attention and image maintenance, see Kosslyn, 1983). As a result, subjects should have a clear image of the animal’s face, but not a clear image of the rest of the figure. We expect, therefore, that subjects will easily detect departures from the original figure when the departures are located on areas that correspond to (what subjects consider to be) the animal’s face, but do poorly otherwise.

Thus, in our task, subjects imaging the duck should reliably choose the unaltered Jastrow figure if offered a choice between it and an alternative differing in the contour of the duck’s face. Likewise, subjects imaging the rabbit should choose the unaltered figure if offered a choice between it


a

a

f;,

b

FIG. 4. Test stimuli for Experiments 14. (a) Unmodified figure. (b) Modification on the duck’s bill. (c) Modification on the rabbit’s nose.

and an alternative differing in the contour of the rabbit’s face. Con- versely, subjects should be less sensitive to the difference between the test stimuli when these differ on the “back” of the animal’s head. In the extreme, subjects will choose randomly between the original and the modified figure in this condition.

The main experiments reported here employ a 2 x 2 design, with subjects either imaging the Jastrow figure as a duck or as a rabbit, and then tested with a choice between the original and a stimulus distorted on the rabbit’s face, or between the original and a stimulus distorted on the duck’s face. The modified duck had a reduced concavity at the junction of the duck’s bill and forehead; otherwise, it was identical to the original duck. For convenience, we will use the abbreviation “DFM pair” (for “duck face modified”) to refer to the test pair including the original figure (Fig. 4a) and the figure with the duck’s face modified (Fig. 4b). Likewise, the modified rabbit was identical to the original, except that we eliminated the indentation that marks the rabbit’s “mouth.” We will use the abbre-


viation “RFM pair” (for “rabbit face modified”) to refer to the test pair including the original and the figure with the rabbit’s face modified (i.e., the pair composed of Figs. 4a and 4~). We predict that subjects imaging the duck will choose the original form if tested with the DFM pair and will choose randomly if tested with the RFM pair. Conversely, subjects imaging the rabbit will choose the original if tested with the RFM pair and randomly with the DFM pair.

EXPERIMENT 1

The first experiment was designed as a pretest of our stimuli to ensure that the alterations made to the test stimuli did not change the overall shape of the figure. We were concerned in particular that alterations might have made the test stimuli more or less prototypical of a duck or a rabbit. For example, the alterations made to the duck’s bill (Fig. 4b) could potentially have produced a more “rabbit-like” figure, leading subjects thinking of their image as a duck to choose the original figure merely because it was more “duck-like” (and likewise alterations made to the rabbit’s face may have produced a more “duck-like” figure).

To guard against this possibility, half of the subjects in the first experiment were led to expect pictures of ducks, and then were shown the DFM pair. They were asked simply to choose, while looking at the pictures, which in the pair was the best, most “prototypical” picture of a duck. The other half of the subjects were led to expect pictures of rabbits, and then were shown the RFM pair. With the pictures still in view, they were asked to choose which of the pictures was the best, most “prototypical” picture of a rabbit.

Method Subjects. Fifteen subjects were included in each of the two cells of the design. In all of the

following experiments subjects were college-age volunteers. No subject participated in more than one experiment in this series.

Procedure. Subjects were run individually. They were instructed that they would be shown two pictures of a duck (or rabbit) and that their task was to choose the “best, most prototypical” picture of the animal.

Results

In choosing the “best, most prototypical” duck, subjects’ choices were evenly distributed between the original and modified form (Table 1). In choosing the “best” rabbit, subjects did show a preference for the original form, but this contrast is nowhere near significant [x2 (1) = 0.38, p > .50].

Discussion Our data clearly indicate no bias in the DFM pair: Apparently, our


TABLE 1 Summary of Results, Experiments 1 and 5

Total number of subjects choosing each figure as the “best, most prototypical” representation

Figure construal Original figure Modified figure

Experiment 1 Duck 8 7 Rabbit 10 5

Experiment 5 Bird I 8 Airplane 9 6

modification to the “duck face” left us with a figure that is neither more nor less “duck-like” than the original Jastrow form. However, the data are not so clear cut with regard to the RFM pair. In selecting the “best” rabbit, subjects chose the original over the modified figure by a ratio of 2:l. This contrast was not even close to being statistically reliable, but this may reflect only the low power of the x2 test.

Consequently, some caution is required in interpreting the results of Experiment 1: It is at least possible that the modified rabbit is “less prototypical” than the original form. As we will see in a moment, though, data from subsequent experiments will clarify the role of prototypicality and will indicate that this factor has negligible impact on subjects’ choices. We turn therefore to the question of interest.

EXPERIMENT 2

Does one’s understanding of an image bias what is included in the image? Experiment 2 turns to this question using the recognition procedure described above.

Method

Experiment 2 employed a 2 x 2 design with both factors (interpretation of the figure and test pair used) between subjects. All subjects were shown the original duck/rabbit figure and asked to inspect their image, Half of the subjects were led to perceive the figure as a duck, half as a rabbit. After a 30-s inspection period, subjects were shown a test pair (either DFM or RFM) and asked to choose which of the two figures best resembled their image.

Subjects. Sixty subjects were included, randomly assigned to one of the four conditions. After the procedure, subjects were asked if they were aware, at any time during the procedure, that the test figure had an alternative interpretation. Any subject who indicated that the figure had more than one construal was replaced. Only two subjects in this experiment reported being aware of the alternative construal.

Procedure. Subjects were first administered Marks’ (1972) Vividness of Visual Imagery Questionnaire (VVIQ). This scale was administered to ensure that the subject population included those who report vivid visual imagery. The VVIQ asks subjects to rate the vivid-


ness of several images on a five point scale. On this scale a response of one indicates an image “Perfectly clear and as vivid as normal perception,” and a response of five is “No image at all, you only ‘know’ that you are thinking of the object.” Thus, subjects reporting highly vivid images yield low numerical scores.

Next, subjects were shown a picture of the duck/rabbit figure. The experimenter attempted to bias subjects’ interpretation by saying, “I am going to show you a picture of a duck” (or “. a picture of a rabbit”). The figure was viewed for 5 s, then removed. This S-s presentation has been shown in previous experiments (e.g., Chambers & Reisberg, 1985) to be sufficient to allow encoding of the figure, but not enough time to allow naive subjects to reconstrue the figure. The experimenter then asked subjects to create a mental image of the picture. Subjects were instructed to give particular attention to the details of the picture. To help subjects understand the instructions, phrases such as “create a mental photograph of the figure” were used.

Once subjects announced that they had formed the image, they were instructed to inspect their image for 20 s. They were told that scanning across their mental image would help them to maintain a clear image. Subjects then rated the vividness of their image, using the response scale from Marks’ VVIQ (the same scale used earlier in the study). Finally, subjects were presented with two test pictures (either the DFM or RFM pair) and were asked to select the drawing that most resembled their image. The test pictures were placed side by side, with right-left position counterbalanced across subjects. Subjects were encouraged to inspect all areas of their image, giving special attention to both the right and left sides, prior to making their choice. Subjects were given as much time as necessary to make their selection.

Results

As can be seen in Fig. 5, subjects who construed their images as a duck were well above chance when making the subtle discrimination between the DFM pair. However, performance was near chance when asked to discriminate between the RFM pair. The results were just the opposite for subjects who construed their image as a rabbit. They performed at levels well above chance when asked to discriminate between the RFM pair and at chance when asked to discriminate between the DFM pair. This contrast between groups was significant by a x2 test [x2 (1) = 11.1, p < .Ol].’

These data allow us to clarify the results of Experiment 1 and, more importantly, the role of prototypicality in influencing subjects’ response

’ In our procedures, one might expect that vivid and clear imagery should facilitate performance. Hence, subjects who made correct recognition choices should be those with more vivid imagery (i.e., with lower VVIQ scores). Likewise, one might expect subjects who made correct recognition choices to have rated the target image itself as more vivid than those who made the incorrect choice. However, these expectations were only weakly sup- ported by the data. In the VVIQ results, none of the relevant contrasts (in this or in the following experiments) reached statistical significance, although in the majority of the cases (13 of the 16 comparisons) the VVIQ means were in the predicted direction. We regard our vividness findings therefore as an interesting lead for further work, but not able to sustain strong conclusions. In addition, it is easy to propose methodological accounts of these weak findings (i.e., the standard concerns about self-report). Given the tentative nature of these findings, we will not discuss them further.


90 - Subjects chose between the original figure and one modified on the

* Duck’s face (DFM pair) Rabbit’s face (RFM pair)

.- Duck Rabbit

Subject’s image

FIG. 5. Percentage of correct recognition for each condition of Experiment 2. (“Correct” in this case means: choosing the original form.)

choices. Experiment 1 left open the possibility of a prototypicality difference within the RFM pair, but indicated no such difference within the DFM pair. Therefore, if prototypicality influenced subjects’ choices in Experiment 2, we would expect some sort of contrast between the DFM and RFM data, with the latter, but not the former, influenced by prototypicality. However, Fig. 5 shows comparable results for the DFM and RFM pairs. This implies that prototypicality has little impact on subjects’ RFM choices. *

Discussion

Subjects’ construal of their images was an excellent predictor of their recognition performance. Subjects chose randomly when the modified stimulus was altered in the area that they considered to be the back of the animal’s head. In contrast, they tended to choose the original stimulus when the modified stimulus was altered in the area that they considered to be the animal’s face. These results are clearly consistent with the claim

* In addition, we emphasize the fact that Experiment 1 yielded no positive evidence for a prototypicality difference within the RFM pair. Nonetheless, caution does seem appropriate here, since the logic of Experiment 1 commits us to asserting a null result. As a further consideration, therefore, we note that any prototypicality effects in the first experiment, if present at all, were extremely weak (i.e., the relevant statistical comparisons were nowhere close to reliable). In contrast, the effects in Experiment 2 are rather robust. This again implies a minimal role for prototypicality in Experiment 2 (and in the subsequent procedures).


that which aspects of the image are maintained (and which aspects are not) is directed by subjects’ construal of their images.

However, we need to be cautious in interpreting this result. For example, it is possible that these data reflect a bias in perceptual encoding. Perhaps subjects who initially think they are looking at a picture of a rabbit attend more closely to the side of the figure depicting the rabbit’s face. Hence, these subjects might encode this side of the figure in more detail (and vice versa for subjects thinking they are looking at a picture of a duck). In this case, Experiment 2’s results might reflect selectivity in perceptual encoding, rather than any selectivity in imagery.

The next experiment sought to rule out this possibility by specifically instructing subjects to change their interpretation of their image after they had created their image. We know from previous work that subjects do not spontaneously discover the duck in their rabbit image, or vice versa. However, if specifically cued about the identity of the new construal, subjects do seem able to impose this new construal on the image. (For discussion of this point see Chambers & Reisberg, 1985; Reisberg & Chambers, 1991.) This will allow us to ask which construal is predictive of subjects’ recognition performance-that which the subjects had in mind at the time of encoding, or that at the time of recognition.

EXPERIMENT 3

As in Experiment 2, half of the subjects were shown the duck/rabbit figure and led to think of it as a duck, and half were led to think of it as a rabbit. All subjects were then asked to create an image of the figure. Following inspection of the image, subjects were given a recognition test. Up to this point, the experiment was simply a replication of Experiment 2. After the recognition test, subjects were informed that “some people can interpret this figure as a rabbit” (or “as a duck” depending on their initial construal) and were asked if their image reminded them of this alternative form. If subjects could, with this instruction, find the new construal, they were given a second recognition test.

If subjects’ interpretation of the image directs what is included within the image, then they should perform quite differently on the second recognition test than they did on the first. That is, in the first recognition test, subjects who encoded the figure as a duck should perform above chance with the DFM pair, and at chance with the RFM pair, and vice versa for subjects who encoded the figure as a rabbit. Once these subjects reconstrued their image, however, this pattern should reverse. Now, for subjects who initially encoded the figure as a duck (but who are now thinking of the form as a rabbit), we expect above-chance performance if tested with the RFM pair. Correspondingly, we expect chance performance for these subjects if tested with the DFM pair. (And vice versa for subjects


who initially encoded the figure as a rabbit but who are now, in the second test, thinking of the figure as a duck.)

Method Subjects. Sixty subjects were included, randomly assigned to one of four conditions. Procedure. The procedure for the first half of the experiment was identical to that of

Experiment 2. Then, following the recognition test, subjects were asked if they could reconstrue their image to match the alternative interpretation suggested by the experimenter. The subjects were informed that “some people can interpret this figure as a rabbit” (or ‘1 . . . as a duck,” depending on their initial construal of the figure). The subjects were encouraged to inspect their image to determine whether they could understand their own image as having this alternative interpretation. To aid them, subjects were given hints, such as attending to the left side of their image to help find the duck, or the right side of their image to help find the rabbit.

Once subjects indicated that they had found the suggested construal of the figure, they were asked to try and maintain their new interpretation for 20 s and, if the old construal “popped” into mind, to reinstate the new construal. Subjects were asked to indicate to the experimenter when the “old interpretation came to mind.” Only one subject indicated that his image altered between interpretations.

After the 20-s inspection period, subjects were again asked to rate the vividness of their image on the same scale used earlier (Marks, 1972). Then they were given a second recognition test using the same test pair (DFM or RFM) as had been used for that subject in the first test.

Results

First recognition test. The results of the first recognition test replicated those of Experiment 2. Subjects who construed their image as a duck performed well above chance when asked to discriminate between the DFM pair. Their performance, however, was at chance when asked to discriminate between the RFM pair (Fig. 6, left panel). The results were just the opposite for subjects who construed their image as a rabbit. The contrast between groups was significant by a x2 test [x2 (1) = 7.94, p < .Ol].

Second recognition test. Thirty-six of the 60 subjects were, with instructions, able to reconstrue their images and so were given the second recognition test. Sixteen of these were subjects who initially understood their image as a “duck;” nine of these had been tested with the DFM pair, seven with the RFM pair. Twenty subjects who initially understood their image as a rabbit were, with instructions, able to reconstrue the figure; 10 of these were tested with the DFM pair, 10 with RFM.

The results of the second recognition test clearly indicate that it is the interpretation of the image at the time of test, not at the time of encoding, that predicts performance. Subjects who changed their construal of the image from a duck to a rabbit performed above chance with the RFM pair, but their performance was near chance with the DFM pair. The results were just the opposite for subjects who successfully changed their con-


Subjects chose between the

~~~~ _..._._______ ; ______._______.. :\\;- . . . . . . . . . .

30 _ 30 -

Duck Rabbit Duck Rabbit

Subject’s initial image Subject’s image at time of 2nd test

FIG. 6. Left panel: Percentage of correct recognition for Experiment 3, Test 1. Right panel: Percentage of correct recognition for Experiment 3, Test 2.

strual from a rabbit to a duck (Fig. 6, right panel). The contrast between groups was significant by a x2 test [x2 (1) = 15.27, p < .Oll.

Discussion

Experiment 3 both replicated and extended the results of Experiment 2. The data indicate that it is subjects’ understanding of the image at the time of test, not at the time of encoding, that predicts recognition errors. Subjects who were able to change their understanding of the image showed a corresponding change in their recognition choices.

However, there is still a problem in interpreting these data. In Exper- iment 3, the initial recognition test provided not only a test, but also a second opportunity to perceive and encode the duck/rabbit figure. It is possible that during this test subjects may have incorporated new details into their image, i.e., they may have enhanced the vague areas of their images. In this way, the subjects’ original encoding might have been incomplete (leading to errors in the first test), but, during the recognition test, subjects may have “picked up” the overlooked aspects of the figure (leading to correct recognition in the second test).

The fourth experiment eliminates this concern by eliminating the first recognition test. That is, the procedure is identical to that of Experiment 3, with the exception that subjects were only tested once after they had (with instructions) reconstrued their images. If the results of this experiment replicate those of Experiment 3’s second test, this will remove the possibility that results of the earlier experiment were due to encoding during the first recognition test.

CHAMBERS AND REISBERG

EXPERIMENT 4

Method Subjects. Sixty subjects were included, randomly assigned to one of four conditions. Procedure. The experiment followed the procednre outlined in Experiment 3 except for

the changes noted below. After subjects had indicated that they had created their initial image, they were asked simply to inspect their image for 20 s. After this inspection period, subjects were informed that many people can interpret the test figure as an alternative form (as a duck or a rabbit, depending on their initial construal). Subjects then inspected their image with the same instructions as those used in Experiment 3. None of the subjects reported that the “old” interpretation came to mind during the inspection period.

After the inspection period, the subjects were given a recognition test. As in the earlier experiments, subjects were asked to choose the figure that most resembled their image from either the DFM or RFM pair.

Results

Thirty-two of the 60 subjects were able, with instructions, to reconstrue their image. Seventeen of these were subjects who initially understood their image as “duck” (10 tested with the DFM pair, seven with RFM). The remaining 15 subjects had initially understood their image as a rabbit (eight DFM, seven RFM).

Subjects who understood their image as a duck at the time of test were well above chance on the recognition task when asked to discriminate between the DFM pair, but their performance was close to chance when discriminating between the RFM pair. This pattern of results was just the opposite for subjects imaging the rabbit (Fig. 7). This contrast was significant by a x2 test [x2 (1) = 6.03, p < .Ol].

60 -

70 -

60 -

50 - Subjects chose between the

original figure and one .._ . . . . . . . . -..I& . . . . . _..

modified on the U Duck’s face (DFM pair) ---t Rabbit’s face (RFM pair)

t&k Rabbit Subject’s image at time of test

(after reconstrual)

FIG. 7. Percentage of correct recognition for Experiment 4.


Discussion

The results of Experiment 4 replicated those of Experiment 3, while eliminating the second “learning trial.” Subjects who were able to reconstrue their image showed corresponding recognition errors.

Experiments 3 and 4 together remove the concern that our data are due to a bias in how subjects encoded these figures in the first place. Instead, the data indicate that the specific meaning given to the image directs which aspects of the image will be clearly depicted and which aspects will be allowed to fade.

However, these claims are based on experiments with a single figure as the stimulus. Could the results somehow be unique to this figure? To address this possibility, the procedure used in Experiment 4 was repeated employing a drawing of the bird/airplane (Tsal & Kolbet, 1985; Fig. 8a).

EXPERIMENT 5

The next series of studies, like the duck/rabbit studies, presented subjects with a choice between the originally presented figure and a modification of it. We need first to ensure, however, that this choice is not biased by the stimuli themselves. Therefore, following the logic of Ex- periment 1, Experiment 5 provided a pretest of the stimuli to be used in Experiment 6.

To create our test pairs, the bird/plane figure was modified on either the “nose of the plane” or the “beak of the bird.” As in the previous experiments these modified figures were coupled with the originally shown figure to create the test stimuli. For convenience we will call the stimulus pair including the original and the figure modified on the airplane’s nose the “ANM pair” (for “airplane-nose modified”). Similarly, we will call the stimulus pair composed of the original and the figure modified on the bird’s beak the “BBM pair” (for “bird-beak modified”).

Method

Subjects. Thirty subjects were included, randomly assigned to one of the two cells of the design.

Procedure. As in Experiment 1, half of the subjects in Experiment 5 were led to expect pictures of birds and then were shown the BBM pair. They were asked simply to choose, while looking at the pictures, which in the pair showed the best, most “prototypical” picture of a bird. The other half of the subjects were led to expect pictures of airplanes and then were shown the ANM pair. With the pictures still in view, they were asked to choose which of the pictures showed the best, most “prototypical” airplane.

Results

As can be seen in Table 1, our stimulus modifications introduced no reliable bias into the stimulus pairs. That is, there was no indication that


a

b

c

FIG. 8. Test stimuli for Experiments 5 and 6. (a) Unmodified figure. (b) Modification on the nose of the airplane. (c) Modification on the bird’s beak.


our modified bird form was any less (or more) prototypical of a bird shape than was the original form and likewise for the airplane. The x2 tests on these contrasts were performed and they proved to be insignificant [x2 (1) = 0.56, p > .30].

EXPERIMENT 6

Given the Results of Experiment 5, we can return to the question of interest. Experiment 6 was essentially a replication of Experiment 4 using the bird/airplane as the test figure.

Method Subjects. Fifteen subjects were included in each of the four cells of the design. None of

the subjects in this experiment reported that the alternative interpretation came to mind without prompting by the experimenter.

Procedure. The experiment followed the procedure outlined in Experiment 4, except that the bird/airplane was used as the stimulus. Half of the subjects were initially biased to perceive the airplane, half to perceive a bird. Following a brief inspection period, they were instructed that some people understand the figure to be a bird (or an airplane, depending on the initial construal). Next, subjects who were able to reconstrue their image were given a recognition test. Half of the subjects were given the BBM pair and half the ANM pair.

Results

Twenty-six of the 60 subjects were able, with instructions, to reconstrue their image. Half of these were subjects who had initially understood their image as an airplane (six tested with the AFM pair, seven with BFM), and half were subjects who had initially understood their image as a bird (seven tested with the AFM pair, six with BFM).

When subjects construed their image as an airplane and were asked to discriminate between the ANM pair, their performance was well above chance (Fig. 9). However performance was at chance for these subjects if asked to discriminate between the BBM pair. The results were reversed for subjects who construed their image as a bird. The interaction was significant by a x2 test [x2 (1) = 10.15, p < .Ol].

Discussion

Experiment 6 speaks to the generalizability of our results. The pattern of results was exactly like those of Experiments 2,3, and 4, indicating that this pattern is not limited to the duck/rabbit figure.

EXPERIMENT 7

In Experiments 3, 4, and 6, subjects were, with specific instructions, able to reconstrue their own images. According to our data, this change in construal led them to “fill in” details missing from their images. Specif- ically, subjects seemed to fill in details about what had been, on their


9,~ - Subjects chose between the original figure and one modified on the

’ * Airplane’s nose (ANM pair)

3 a0 _ ----C Bird’sbeak(BBMpair) .s .P b

$

70 -

40 - 1 Airplane Bird

Subject’s image at time of test (after reconstrual)

FIG. 9. Percentage of correct recognition for Experiment 6.

initial construal, the back of the form’s head. Simultaneously, the data indicate that, with the change in construal, subjects “let go” of details about the “side” of the image that had been, on the initial construal, the form’s face.

It is important to be clear, however, about just what this “filling in” entails. Consider a subject initially imaging the figure as a duck. This subject clearly has incomplete information about the figure’s right side (the rabbit’s face). We cannot tell from the data exactly what is missing from the image; perhaps the subject has no information at all about this contour, perhaps he or she is merely missing certain nuances from the contour. One way or the other, though, the data do tell us that this subject is missing the information needed to discriminate between the RFM pair and, as a result, performance with this pair is at chance levels. After reconstrual, though, this same subject seems to have much-improved information about the figure’s right side. This is revealed in good performance with the RFM pair. Apparently, the subject “reinstated” the information initially missing from the image. But this reinstatement must be done correctly: the differences among our test stimuli are small, and so if one’s image departed even slightly from the original form, the image would not support correct judgments. Thus, before the reconstrual, our hypothetical subject is missing information about the rabbit’s face; after reconstrual, the subject has precise and accurate information about this contour.

This obviously raises a question: Where does this “reinstated” contour


come from? According to the first recognition test, the subject was plainly missing key information about the relevant contour. Presumably, therefore, the contour is not being filled in from memory. But what is the alternative? Perhaps subjects filled in the information missing from their images based on general knowledge of what a duck or a rabbit looks like, rather than specific knowledge about the test figure itself. In this case, however, it is not clear how subjects worked their way back to the original contour. After all, Experiments 1 and 5 tell us that the original and modified forms resemble the relevant prototypes equally. Thus, if subjects are reconstructing their images based on something like a prototype, their construction is as likely to produce an image of the modified form as it is to produce an image of the original form. But this is not what the results show; instead, the results indicate that the image (after reconstrual) really is “restored” to its original form. This seems to imply that the “reinstatement” of the image, after reconstrual, could not be based on general knowledge, but must be based on some remembered information about the original Jastrow figure itself.

In the spirit of caution, however, we performed an additional experiment to test this claim. (This caution seems necessary for several reasons, including the concerns expressed earlier about Experiment 1.) Consider the possibility that subjects reinstated their images without benefit of memory of the original form. Roughly speaking, the hypothesis is that subjects initially have an image with a “gap” in it (i.e., the vague contour) and till this gap based on generic knowledge of some sort. If this is correct, then we would expect comparable completions from subjects who had never seen the figure before (and who therefore must, of neces- sity, be filling the “gap” based on generic information). Experiment 7 tested this prediction.

A new group of subjects was presented with a duck/rabbit figure with a segment missing from the contour. These subjects had never seen the original, intact figure. The subjects’ task was simply to “complete” these forms-i.e., to draw in the missing section of contour. For half of the subjects, the missing segment was from the rabbit’s face, mimicking the (hypothesized) mental image of a subject thinking of the figure as a duck. For the other subjects, the missing segment was from the duck’s face, presumably mimicking the effects of a rabbit construal. To make this design as conservative as possible, we wished to make the reinstatement of these figures as easy as possible. Thus, we kept the size of the missing segment small, confining it to the segment that actually distinguished the original form from the two modified figures used in Experiments 14.

There were four types of “drawing subjects.” Overall, half were given a figure with its gap on the left side and half a figure with its gap on the right. Within these groups, half were asked to complete the figure so that


it would look like a duck and half to complete it so that it would look like a rabbit. Each of these drawings was then given to a new subject, who was asked either to compare the drawing to the RFM pair or the DFM pair. These “choosing subjects” were asked to select the figure from within the test pair that most resembled the completed drawing.

If generic knowledge is a sufficient basis for “restoring” these figures, then “drawing subjects” will fill in the missing contour in a manner that tends toward the original Jastrow form, not our modifications of it. In this case, the “choosing subjects” will select the original figures as most resembling the drawing. On the other hand, “restoring” this figure to its original shape may require some memory for this contour. If this is true, then drawing subjects (without such a memory) are likely to produce pictures that resemble the original and modified forms equally. This would lead to the expectation that choosing subjects will select randomly between the original and modified forms.

Method There were eight cells in this design. Drawing subjects were instructed to draw either a

duck or a rabbit, filling in either a left-side or right-side gap. This yields four groups of drawings. Each drawing was then shown to two choosing subjects, one of whom compared it to the DFM pair and one who compared it to the RFM pair.

Subjects. Sixty subjects were randomly assigned to one of the four drawing conditions. An additional 120 subjects were randomly assigned to one of the eight choosing conditions.

Procedure. Half of the drawing subjects were asked to complete the figure so it resembled a rabbit, and half were asked to complete the figure so that it resembled a duck. Within each of these groups, half of the subjects were given a figure with a gap to till in on its left side and half a figure with a gap on the right side (Figure 10).

Each of the 60 drawings thus produced was then shown to two new subjects (the choosing subjects). For each drawing, one choosing subject was asked to compare the drawing to the DFM pair, and one was asked to compare the drawing to the RFM pair. All choosing subjects were asked to select the figure within the test pair that most resembled the drawing.

Results

As predicted, the choosing subjects tended to choose randomly in six of the eight groups, as indicated by a x2 test (Table 2 for percentage correct and x2 values). That is, choosing subjects were equally likely to indicate that the drawings resembled the original and the modified form.

However, two cells of the design did not show this pattem.3 Consider first drawings that were created by subjects who intended to draw a duck filling in the right-hand gap. These subjects tended to draw a smooth

3 Note that these two reliable contrasts may be spurious, given the number of comparisons required for this procedure. Nonetheless, these contrasts are contrary to our predictions and therefore the conservative strategy is to examine them and not to set them aside as spurious.


0

f ?

Q

b FIG. 10. Test stimuli for Experiment 7.

contour to complete the duck’s head. That is, they omitted the indentation that marks the rabbit’s nose. Thus, their drawings did resemble the modified figure within the RFM pair, and the data from choosing subjects reflect this. By the same token the rabbit’s nose was actually present in the left-gap figures and so obviously included in the drawings completing these figures. This feature clearly can guide responding with the RFM pair, and this is reflected in the choosing subjects’ data (RFM pair; left gap). Note though that this feature is part of the figure supplied to drawing subjects and not a consequence of the drawing. Consistent with this, similar data were obtained when subjects intended a duck drawing and when they intended a rabbit drawing (60% vs 66%).

TABLE 2 Percentage “Correct” and x2 Values for Experiment 7

Location of gap in initial figure

Drawine subiects intended:

Gap on left side

Duck Rabbit

Gap on right side

Duck Rabbit

DFM pair 53 46 40 40 Choosing subjects x2 = 0.18 x2 = 0.18 x* = 2.0 x2 = 2.0

chose within: RFM pair 60 66 26 46 x2 = 2.0 x2 = 5.12* x2 = 11.52* x2 = 0.32

Note. ‘Correct” responses indicate choosing the origina/ figure. * p < .05. All other p values >.lO.

168 CHAMBfiRS AND REISBERG

Discussion

Overall, subjects complete this form so that it resembles the original Jastrow figure only if they have previously seen (and remember) the original (unaltered) shape. Without this prior exposure, subjects completed this figure so that it resembled our altered forms as much as it resembled the original. In six conditions, choosing subjects indicated that the drawing resembled the original and modified forms equally. In the seventh condition the drawings resembled the modified form more than they resembled the original; in the eighth condition, the drawings most resembled the original form.

In contrast, subjects in our earlier procedures did “restore” their image so that it resembled the original shape more than the modified versions. This clearly implies that subjects in the earlier procedures were “filling in” the missing contour based on some memory of the original figure, not on generic knowledge. This is despite the fact that these subjects, prior to the reconstrual, showed no evidence of remembering the relevant contour’s shape. We will consider, in the General Discussion, how these findings can be explained.

GENERAL DISCUSSION

These studies have examined the claim that image construal guides what is and what is not included within the image. Subjects who construed their image as a duck and were shown the DFM pair were suc- cessful in our task, while subjects shown the RFM pair performed at chance levels. The results were just the opposite for subjects who thought of their image as a rabbit.

These results are clearly consistent with our hypothesis and also pro- vide a straightforward account of the Chambers and Reisberg (1985) results. In those earlier studies, subjects routinely failed to discover the duck in a rabbit image and vice versa, despite training, coaching, and hints. According to the current results, subjects imaging the duck/rabbit form as a duck simply have a different image from those imaging it as a rabbit-mphasizing different aspects of the shape and, conversely, omit- ting different aspects. Thus, information necessary for the rabbit construal may literally be absent from the images of subjects seeking to image the duck (and vice versa for subjects thinking of their image as a rabbit). It is no wonder then that subjects imagining the duck failed to find the rabbit and vice versa.

The present data, therefore, make it plain that subjects’ construal of their image (as a duck or as a rabbit) plays an important role in shaping the image’s content. We note, however, that there are several ways to think about this role. The first possibility is that subjects’ understanding of the


image is effectively part of the image itself. One might propose, for example, that mental images are represented by something akin to a struc- tural description in which depictive and descriptive information are inte- grated into a single representation. Alternatively, one might argue that the depictive information within an image is obligatorily understood within a “perceptual reference frame,” with the reference frame specifying such aspects as orientation, figure/ground, and so on (cf. Peterson, Kihlstrom, Rose, and Glisky, 1991). In either of these formulations, the Reisberg and Chambers (1991) data, described earlier, indicate that learning from imagery will occur only when the target information is compatible with all the information within an image-that is, with both the depictive and the descriptive elements of a mental image. Moreover, the present data indicate that the depictive and descriptive elements of an image are not in- dependent. Instead, the present data draw our attention to the interaction between these elements, with the descriptive aspect of imagery literally shaping the depictive aspect.

At the same time, though, the present data can also be read in a different fashion, one consistent with more conventional views of imagery. Rather than arguing that the understanding of an image accompanies (or is a part of) the image, one could claim that the understanding of the image plays its role in the creation of the image. Once created, the image could then be represented in some neutral form, perhaps as a pixel pattern within an imagery buffer (cf. Kosslyn, 1980, 1983). This pixel pattern would be marked by its “history” such that the pixel pattern created to be a duck image (for example) would include different material than one created to be a rabbit image (in accord with the present data). Thus the intention would in this sense be actualized in the image, and so its influence would remain in place as long as the image existed. Nonetheless, the image, with that specific pixel pattern, would function much as a stimulus-perhaps realized in some buffer in the visual system, processed through the normal channels of vision, and so on.

This latter claim is fully compatible with the present results and therefore also with the Chambers and Reisberg (1985) results. However, it is not clear how it fits the Reisberg and Chambers (1991) data. For example (and as described earlier), Reisberg and Chambers (1991) had subjects encode a geographical figure in a novel orientation. Subjects were then asked either to imagine the form rotated or to change their “assignment” of the image’s top. They were then asked if their images reminded them of a familiar form. Many subjects in the “reassign” condition, but none in the “rotate” condition, were reminded of a new form. This is consistent with the claim that the depictive and descriptive aspects of imagery are unified in a single representation, since the reassign condition should have led to a revision in the image’s “reference frame,” while the rotate con-


dition should not. However, it is not clear how to understand these results in terms of pixel patterns, since presumably, both the rotate and the reassign conditions should have led to a new pixel pattern. Hence, we believe the full pattern of evidence favors the “dual aspect” view. None- theless, this is clearly a point on which further data are needed.

Returning to the present data, recall that when subjects changed their interpretation of their images (Experiments 3, 4, and 6), details that had been available to them became unavailable, while at the same time, details once absent were “filled in.” The results of Experiments 1, 5, and 7 argue that subjects were not merely filling in the vague areas of their images via generic information. Instead, subjects seem to need some memory of the specific duck/rabbit figure. But this creates a paradox: If subjects have some memory for the entire figure, why is performance so poor in some conditions? That is, why are subjects unable to make judgments about the back of the imaged animal’s head? On the other hand, if subjects do not remember the entire figure, then we can explain the poor recognition performance, but how were subjects able to restore their image when they reconstrued it?

Perhaps, despite our earlier claims, images do contain full information about the entire figure. In this case, it is easy to explain how subjects reinstate the contour, because there is no reinstatement to be done. To explain the recognition data, one might simply argue that there are limits on subjects’ access to the imaged information. That is, perhaps the processes of image inspection are directed by subjects’ construal of the image. Thus, images might contain both details of the duck’s face and of the rabbit’s face, but when subjects inspected their images, they attended only to areas of the image corresponding to what they thought of as the face. Hence, subjects succeeded on the recognition test when the test stimuli differed on these attended areas and failed when the test stimuli differed on unattended areas. On this view, when we asked subjects to change their interpretation of the image (in Experiments 3, 4, and 6), subjects simply shifted their attention to a new area of their image, and hence a new set of features became available to them.

This view finds support in the Tsal and Kolbet (1985) data, indicating that construal does in fact bias attention. But the attention effect docu- mented by Tsal and Kolbet seems far too weak to handle our imagery results: in our data, subjects were effectively at chance in making discriminations about the back of the (imaged) animal’s head. Hence, we cannot argue that their attention is merely biased away from the relevant region. Instead, we would have to argue that subjects were, for some reason, completely unable to attend to the relevant region. This is all the more remarkable given that much in our procedure signaled to the subject where the relevant features were located. For example, subjects were


instructed during the test to direct their “mind’s eye” to different areas of the image. In addition, the stimuli themselves should have cued subjects to scan their images: A subject confronted with the RFM pair, for example, can easily see that the test stimuli differ only in the contour at the pictures’ right edge. This would presumably lead subjects to inspect the rightmost “edge” of their images in order to make the required comparisons.

All of this, we believe, makes implausible the claim that our subjects’ images were complete, but that parts of the image were inaccessible. We know that subjects can scan their images (Kosslyn, 1980, 1983). Our instructions urged subjects to scan their images. Our stimuli should have signaled to subjects the need to examine specific areas of their images. Despite all this, subjects failed to find in their images the information needed for making the comparison of the test stimuli. All of this implies that it is not image inspection that is selective, but the image content itself. We turn, therefore, to an examination of that proposal.

The alternative explanation of our data is of course the one we have been entertaining all along-that images are not fully maintained, but are precise only in areas of the image that correspond to what subjects think of as the front of the animal’s head. This account easily explains subjects’ performance in our recognition tests. As we have already seen, though, this account needs some elaboration to explain how subjects were able to restore their images when they changed their construal of the figure.

Kosslyn (1980, 1983) has argued that images are constructed by drawing on information in “image files” in long-term memory. When an image is built, subjects first construct an image “frame” and then add details to this frame as needed. It is this active image, in working memory, that is available for inspection, scanning, and so on. In these terms, our subjects might have reasonably complete knowledge of the duck/rabbit figure in their image files. However, this information in long-term memory is not available to subjects in making their recognition choices. Instead, these choices are based on their inspection of the active image itself, which contains less information than is contained in the image tiles. In particular, the active image contains the face of only one of the animals-the left-most side of the figure for subjects who understand their image as “duck” and the right-most side for subjects who understand their image as “rabbit.” Thus, there is no contradiction between chance performance on the recognition test and the ability to reconstruct the figure accurately. The former reflects information missing from the active image, the latter reflects information present in the image file.

All of this poses several questions for future research. First, our data document that images are far less clear about the “front” of the imagined animal’s head than about the “back.” In particular, the former will sup-


port fine discriminations, the latter will not. But, as we have mentioned, this leaves open the question of what is missing from the image’s vague areas. Is there no “back-side information” at all? Is there intermittent information about the back, as the portion of the image is refreshed only rarely? Or is it merely detail that is omitted from this aspect of the image? These various possibilities are all compatible with our claim that image construal governs what is depicted, but have different implications for the relation between the image file and the active image and, correspondingly, different implications for the nature of image maintenance.

Likewise, it seems important to ask what sorts of instructions, cues, or strategies will “trigger” a revision of the active image, drawing on some new subset of the information in the image file. Some pertinent results are already avaiIable: Chambers and Reisberg (1985) found that subjects, seeking to reconstrue the duck/rabbit image, were not helped by instructions to examine first the “left” then the “right” sides of the image. In present terms, this instruction seems not to have changed the pattern of information available in the image and therefore resulted in no new discoveries. In contrast, a number of studies have shown that subjects can reconstrue this image if specifically urged to think of the “front” of the figure as being the “back” and vice versa (Brandimonte & Gerbino, 1991; Hyman & Neisser, April 1991; Livingston & Christensen, 1991; Peterson et al., 1991). These results clearly resemble those reported by Reisberg and Chambers (1991); in all of these cases, subjects are verbally led to change their understanding of their images, and this in turn leads to image discoveries. But, for present purposes, it seems that this “front/back” instruction is sufficient to elicit a change in the active image, presumably filling in what was previously vague and letting go of what was previously clear. At this point, work is needed to clarify why some instructions have this effect while other instructions do not (e.g., Chambers & Reisberg, 1985). Peterson et al. (1991) offer one account of this, and examination of this account seems an important avenue for future research.

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American Journal of Psychology, 71, 612-613. (Accepted November 13, 1991)

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What an image depicts depends on what an image means

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