CHAPTER FOUR

The Cognitive Approach I: History, Vision, and Attention

Why a Cognitive Revolution? Inadequate behaviorist accounts of

language acquisition. Reinforcement cannot explain rapid learning of vocabulary and syntax.

New tools for measuring brain activity.

The rise of the computer as a metaphor for mind and the adoption of the information- processing perspective.

Cognitive Psychology

Neisser (1967) one of its early proponents.

The study of human knowledge representation and use.

Employs experimentation, modeling, and computer simulation.

Represents mental activity using a process model, a diagram with boxes and arrows that indicate information processing between successive stages.

Modularity of Mind

Mind consists of functionally independent modules (Fodor, 1983).

Modules are hardwired, domain-specific, fast, automatic, stimulus driven, and informationally-encapsulated.

E.g. reading

Deficit studies offer both positive and negative evidence of such modularity.

Perception

The process by which we gather and interpret information about the outside world via the senses.

Vision

Two stages in vision

• physical reception of stimulus

• processing and interpretation of stimulus

The Eye - physical reception

mechanism for receiving light and transforming it into electrical energy

light reflects from objects images are focused upside-down on

retina retina contains rods for low light vision

and cones for color vision ganglion cells (brain!) detect pattern and

movement

Interpreting the signal

Size and depth visual angle indicates how much of view

object occupies(relates to size and distance from eye)

visual acuity is ability to perceive detail (limited)

familiar objects perceived as constant size (in spite of changes in visual angle when far away)

cues like overlapping help perception of size and depth

Interpreting the signal (cont) Brightness

subjective reaction to levels of light affected by luminance of object measured by just noticeable difference visual acuity increases with luminance as does

flicker

Color made up of hue, intensity, saturation cones sensitive to color wavelengths blue acuity is lowest 8% males and 1% females color blind

Interpreting the signal (cont) The visual system compensates for:

movement changes in luminance.

Context is used to resolve ambiguity

Optical illusions sometimes occur due to over compensation

Ambiguity

Optical Illusions

the Ponzo illusion the Muller Lyer illusion

Reading

Several stages: visual pattern perceived decoded using internal representation of language interpreted using knowledge of syntax, semantics,

pragmatics

Reading involves saccades and fixations

Perception occurs during fixations

Word shape is important to recognition

Contrast between text and background matters

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Pattern Recognition

The ability to identify objects in the environment.

One of the main functions of perception.

There are many theories of how it takes place.

Template Matching Theory

An image generated from a stimulus is matched to an internal representation called a template.

The Pandemonium Model of Feature Detection

Feature Integration Theory

• Used to explain visual search, in which we attempt to locate a target object hidden among distractors.

• During the preattentive stage, features pop out effortlessly. Attention is not required. Search occurs in parallel.

• During the focused attention stage features are combined together to create object representations. Attention is required. Search is serial.

Visual SearchParallel search Serial search

Attention

A form of mental activity or energy that can be distributed to different tasks.

Attention is:1. Selective2. Divisible3. Shiftable4. Sustainable

Theories of Attention

Bottleneck theories explain the narrowing of attention that enters conscious awareness.

Capacity theories explain how attention is distributed to different informational sources.

The Filter Model

Broadbent’s (1958) filter model of attention.

Information is selected on the basis of physical characteristics.

The selected information is allowed to pass to later stages where it undergoes further processing.

Unselected information is blocked completely.

An example of an early selection model.

The Attenuation Model

Formulated by Treisman (1964).

Unattended message is not blocked completely but attenuated.

The likelihood of information getting through is determined by its threshold.

The Deutch-Norman Selection Model

Attributed to Deutch and Deutch (1963) and Norman (1968).

Selection happens later in the attentional processing sequence.

It is therefore an example of a late selection model.

Selection is based on the semantic content of the message, its meaning.

The Multimode Model of Attention Allows for selection to take place early or

late.

The filter is “moveable” and can take place at various stages of processing based on the observer’s needs.

Selection can be based on physical or semantic characteristics.

The Capacity Model of Attention Proposed by Kahneman (1973).

Attention is a limited resource.

Arousal level determines capacity.

Where attention goes is determined by enduring dispositions and momentary intentions.

Interdisciplinary Crossroads: Computational Vision

Marr (1982) specifies the steps a computer would go through to recognize an object.

1. Image is transformed into a raw primal sketch with a distribution of intensity values.

2. The 2 1/2-D sketch contains groups of features, surfaces, and layout.

3. The 3-D sketch is a three-dimensional interpretation complete with linked object parts.