The Cognitive Dog Class 12: A little bit about statistics and alot about cue use.

The Cognitive Dog

Class 12: A little bit about statistics and alot about cue use

Agenda

• Questions about the 2nd assignment...

• Get those extension requests in on or before the 21st.

• Looking ahead

• Statistics in 15 minutes

• What we know about the use of gestures by dogs to guide their choice

Looking ahead...

The big picture

• Do pet dogs use human cues (gestures, gaze, body position, motion, voice) to guide their behavior?

• Well, do they?

• If so, to what feature are they attending?

• Why are they using the feature?

• What mental representation do they build, i.e., is it a ‘simple’ association or do they understand the meaning of the cue at some ‘deeper’ level.

• What larger story does this tell?

The big picture continued...

• The larger story...

• Is it a difference in underlying ability, or in performance?

• Are the observed differences, side-effects of changes in other behavioral systems, or were they directly selected for, i.e. a social cognition gene?

• If the differences are due, in part, to genetic differences, what is the nature of those differences?

• And how do we discover this?

The cognitive tasks we are going to examine

• Use of pointing gestures (this week)

• Object Permanence, Invisible Displacement, Means-Ends (next week)

• Social Learning (week we get back)

• Use of acoustic cues (words...)

• The big theme...

• Dogs are masters of using simple but reliable rules to make sense of a complicated world, so indeed, they may be doing just enough to get by.

But first, statistics in 15 minutes...

“If your experiment needs statistics you ought to have done a better experiment...”

-Lord Rutherford

Characterizing data...

• I am the marketing manager of “Destruct-Not” chew toys and I want to say something about how long they last. So I probably need...

• Some measure of the average or mean time that they last: also known as the mean, e.g. 10 minutes.

• Some measure of the spread or variation around the mean, e.g., for some dogs they last 1 minute, for other dogs they last 15 minutes, for most dogs they last between 8 and 11 minutes.

Variance and standard deviation measure

spread

The normal distribution

Hinton, P. R. (2004). Statistics Explained. London, UK, Routledge.

The normal distribution characterizes how values tend to be distributed around the mean, and also the probability of observing

a given value given that distribution

Hypothesis testingis the probability of observing a given value likely given what you know about the population


Significance...

• Significance is a statistical term that indicates the level of confidence in rejecting the null hypothesis, or that you are seeing a real effect. BUT, just because you are seeing a real effect does not mean that it is an important effect, e.g.,

• Choosing 51/100 may be statistically significant from 50/100, but in the grand scheme of things, it may not be important.

• When you see p <.01, that is to be read as “There is a 1% chance of seeing this result if the null hypothesis is true.”

Example

• Known distribution: length of time required to destroy current “Destruct-Not” chew toy.

• Null hypothesis: new and improved “Destruct-Not” chew toy is no better than old toy.

• Test and see where results lie relative to ‘known’ distribution

• Accept or reject null hypothesis


Samples vs. Population

• Population: complete set, e.g., all dogs that use “Destruct-Not” chew toys

• Sample: a subset of the population.

• To be useful, a sample needs to be a ‘representative’ subset of the population. Questions to ask?

• How big does the subset need to be?

• How do you choose members to be in that subset?

• How do you test?

Sample size and the pooling fallacy...

• Intuitively, the bigger the sample size, the more representative your sample will be: by representative, I mean it has a mean and variance that accurately reflects the population.

• But it needs to be the right kind of bigger. Which sample will be more representative...

• Test 10 different dogs each of a different breed & measure how long it takes them to destroy a new “Destruct-Not” toy.

• Test 10 different dogs from “toothless terrier manor” & measure how long it takes them to destroy a new “Destruct-Not” toy.

• Test “Chomper” 10 times & measure how long it takes him each time to destroy a new “Destruct-Not” toy.

The T-statistic

• In practice, you don’t know what the population standard deviation is, so you need to estimate it using your sample.

• That estimate of the standard deviation needs to be adjusted to reflect that it is based on a certain number of samples

• The t-statistic corrects for this.

• e.g., T(9.77) = 7, P<0.001

99% Confidence, 5

samples

99% Confidence, 20

samples

Pooling artificially makes the standard deviation smaller, so you

are more likely to see a “significant” result

You see the pooling fallacy in almost every experiment of dog cognition!!!!!!

• To increase the sample size the experimenters test the same dog multiple times and treat each time as an independent measurement...

• But it isn’t an independent measurement because it is the same dog doing it.

• 10 dogs each doing the point test 10 times should be considered 10 samples, not 100. The average for each dog should be considered a sample.

• The practical effect of the pooling fallacy is that it makes the spread smaller than it may be in reality, and make it more likely to reject the null hypothesis, e.g. rejecting the hypothesis that the dog is responding at chance levels.

Std Deviation vs. Std Error

• Those deceiving little bars...

• SE = SD divided by the square root of the number of samples

• As usually shown overstates difference. Doubling SE gives a better sense of how different the means are (95% confidence)

More things to think about regarding a representative sample...

• What is the criteria for choosing dogs?

• What is the setting in which you test the dogs: home, dog-park, vet’s office, lab-setting...?

• What is the criteria for measuring the time?

• When do you start timing?

• When do you stop timing: what is the criteria for “destroyed”

• Is the criteria objective, or does it rely on the judgement of the tester?

Even more things to think about...

• Is your test

• Reliable

• Accurate

• If testing the same dog multiple times, is there a learning effect?


Coming to the wrong conclusion...

• Type 1 error: being fooled by an ‘outlier’ into rejecting the null hypothesis (rejecting green point)

• Type 2 error: being fooled by a point that is consistent with null hypothesis into accepting it (accepting purple point.)

• Reducing one type of error tends to increase other.

Avg. minutes before total distruction for new and improved ‘Destruct-Not’

toy

Sample 1

Sample 2

Is it new and improved?

The take-home message...

• Lord Rutherford had a point...

• Pay attention to the details of the experiment. Those are the things that you as a dog person can evaluate: how were subjects selected, are there things in the experimental set-up that might have affected the animal’s performance, are there alternative explanations, what was the experimenter’s bias and did they control for it, what is the rule of motivation/learning/emotion in shaping the dog’s response.

• If you care, get someone who understands statistics to read over the paper. Even peer-reviewed journal articles contain flaws in statistical analysis.

Dogs use of pointing gestures...

Pointing gestures as cues

Experiments do try to control for olfactory cues

Hare, B. and M. Tomasello (2005). "Human-like social skills in dogs?" Trends in Cognitive Science 9(9): 339-444

Miklosi, A. and K. Soproni (2006). "A comparative understanding of the human pointing gesture." Animal Cognition 9: 81-93.

Things to note about experiments

• Small number of subjects with repeated trials

• Criteria is statistically different than chance

• Results are typically aggregated

• Typically subjects are adult pet dogs recruited from local training clubs, friends, etc.

Hare 2002

Hare 2002The difference between dogs & chimps was startling, and the question was why?

Hare, B., M. Brown, et al. (2002). "The domestication of social cognition in dogs." Science 298: 1634-1636.

9 out of 11 dogs used cue vs. 2 out of 11 for chimps

Hare’s Three Hypotheses (2002)

• “Canids in general are unusually flexible in the types of social information they can exploit”

• “Domestic dogs ... have learned their skills during their individual ontogenies”

• “Selection pressure on dogs during process of domestication for specific skills of social cognition and communication with humans”

Dogs performed differently than

‘socialized’ wolves

This suggested to Hare that it wasn’t an ability common to canids


No wolf performed above chance using any cue. 7 dogs used GPT, 5 used GP, 4 used P to find food above chance. 3 dogs used all 3 cues, 3 dogs used 2, and 1 dog used just one.

Gaze, point, touch

Gaze, point

Point Control

Litter raised pups did the same as family

raised pups

This suggested to Hare that it wasn’t developmental


Differences aren’t significant, but interesting that litter-reared did better than family raised.

9-12 week pups did as well as 17-24

week pups

This suggested to Hare that there wasn’t a learned component

Hare’s big conclusion

• “These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways.”

Things to think about...

• Are there flaws with the experimental design and analysis?

• There is an assumption that socialized wolves are the same as socialized dogs. Is this valid?

• There is an assumption that extensive contact with humans prior to 8-12 weeks is required for pups to preferentially attend to humans. Is this valid?

• There is an assumption that social learning doesn’t occur prior to 8-12 weeks. Is this valid?

• There is an assumption that you can describe a generic pet dog, and that one can generalize across breeds. Is this valid?

Soproni (2002)

Soproni, 2002 tried to characterize performance

Soproni, K., A. Miklosi, et al. (2002). "Dogs' (Canis familiaris) Responsiveness to Human Pointing Gestures." Journal of Comparative Psychology 116(1): 27.

Soproni, cont...

Standing in middle

Standing near one bowl or another

Soproni, K., A. Miklosi, et al. (2002). "Dogs' (Canis familiaris) Responsiveness to Human Pointing Gestures." Journal of Comparative Psychology 116(1): 27.

Soproni...

• Results

• Hand position more important than movement

• static gesture vs. dynamic gesture

• When gesture isn’t clear uses body position as a cue

Miklosi (2003)

Miklosi - 2003

• Statement: behavioral changes [ability to use human cues] have a genetic basis because of the “selection pressure for dogs that were able to adapt better to the human social setting.”

• Question: what is the exact nature of the behavioral changes that have occurred as dogs evolved from wolves?

• Motivated by belief that the original Hare experiment did not control for “differential level of socialization”

• Hare: semi-socialized adult wolves from Wolf Hollow

• Miklosi: hand-raised wolves (n=4) living in a farm setting. Testing started at 4 months and continued for 3 months, every week.

wolves with ‘comparable socialization’ learned to use

cue

One wolf was 80% accurate using distal pointing

Miklosi, A., E. Kubinyi, et al. (2003). "A Simple Reason for a Big Difference: Wolves Do Not Look Back at Humans, but Dogs Do." Current Biology 13(9): 763.

Note: axis is incorrectly

labeled

Median duration of glances at person

Dogs looked back at person sooner & longer

This suggested to Miklosi that dogs were genetically biased to attend to people


Median latency before looking at

person

Note wide variance (i.e.,

some dogs did persist at task & others gave up right away)

Miklosi’s interpretation

• Wolves aren’t as good at using human cues as dogs because of “their decreased willingness to look at the human”

• Conversely, “preferential looking at the human seems to be a genetic predisposition of dogs”...

• at this is the “foundation on which developmentally canalized complex communicative interactions can emerge between man and dog”

• In other words, a genetic bias to look at people was a precursor to the co-evolution of dog-human communicative skills.


Things to think about?

• The idea is appealing, but in this experiment are we just seeing a variance with respect to persistence and frustration?

• lots of terriers don’t look back either...

• wide variance in their own sample

Hare 2005

Hare 2005

• Hare’s statement: “dogs have an unusual ability for reading human communicative gestures... seems to have evolved during domestication”

• Hare’s question: “unclear whether this evolution occurred as a result of direct selection for this ability... or as a correlated by-product of selection against fear and aggression toward humans”

• Decided to test hypothesis using domesticated foxes that were explicitly bred to have reduced fear and aggression toward humans

Hare, B., I. Plyusnina, et al. (2005). "Social Cognitive Evolution in Captive Foxes Is a Correlated By-Product of Experimental Domestication." Current Biology 15: 226-230.

Pups & domesticated fox kits performed similarly

This suggested to Hare that this skill was a by product of selection for tameness


Pups & fox kits between 8-16

weeks

Temperament of farm foxes may interfere with

performance

This experiment was consistent with Hare’s view that this skill was a side-effect of breeding for temperament


Hare’s conclusions...

• 2 alternative explanations for dog’s ability to read human signals

• Communication hypothesis: this ability was directly selected for during domestication

• Correlated by product hypothesis: this ability is simply a by-product of selection for tameness

• He believes his results support correlated by-product hypothesis...

• Nothing was being selected for other than tameness (e.g., ability to read human cues) and yet foxes did as well as pet dog pups

Is this the whole story?

• Hare’s argument: lowered emotional reactivity was selected for, and at a minimum, this set the stage.

• How much more is needed?

• Miklosi’s argument: that is not the whole story, social skills were selected for as well...

Things to think about...

• At one level, all Hare is saying is that cognition takes place in an emotional context. This highlights the central role that emotions and temperament play in a dog’s choice of what to attend to, and what to do.

• This is why we have devoted so much time to emotion and temperament

• What are the specific mechanisms that make a pet dog emotionally prepared to interact & attend to humans?

• This is why we devoted so much time to development

Is this a general feature of domestication?

Contrary to what one might think, cats pay

attention too...

Miklosi, A., P. Pongracz, et al. (2005). "A Comparative Study of the Use of Visual Communicative Signals in Interactions Between Dogs (Canis Familiaris) and Humans and Cats (Felis catus) and Humans." Journal of Comparative Psychology 119(2): 179-186.

Wobber (2005)

Wobber’s two wave model...

• First wave

• Reduction in reactivity set the stage for enhanced ability to use human cues

• This occurred as dogs evolved from wolves, largely as a function of natural selection

• Second wave

• Artificial selection resulted in enhanced ability to use human cues

• and/or, breeds with differential ability to use specific kinds of human cues.

Wobber, V. (2005). The evolution of cooperative signal comprehension in the domestic dog (Canis Famiaris). Department of Anthropology. Cambridge, MA, Harvard University. Bachelor of Arts 115.

Wave 1: tested NGSD vs. ‘newer’

breeds

Are NGSD really a primitive breed?


Results suggested both wave model


• Huskies and Retrievers were considered ‘working dogs’, whereas Basenjis and Toys were considered ‘non-working’

• Huskies and Basenjis considered ‘wolf-like’ breeds, whereas Toys & Retrievers considered non-wolf-like.

• Note variance in performance across dogs and breeds...

Compared cue use across several groups


Modest evidence, at best of a difference


Suggests second-wave enhanced specific cue use

traits

as opposed to a generally enhanced ability to use human cues


McKinley

McKinley

• Tested ability of horses and dogs to use pointing & gaze cues...

• This isn’t the cognitive horse, but let’s just say that the horses didn’t distinguish them on this task.

• “Working gundogs with specialized training used pointing more successfully than pet dogs, and gundog breeds performed better than non-gundog breeds”

• In other words, depends on genes, development and learning...

McKinley et al

McKinley, J. and T. Sambrook (2000). "Use of human-given cues by domestic dogs (Canis Familiaris) and horses (Equus caballus)." Animal Cognition 3: 13-22.


Genes and ‘learning to learn’ may

matter!!!


Working gun dogs

improved dramatically

Mckinley

• The point is that there is a variance in performance from dog to dog that is often masked by aggregated numbers...

• The variance is the result of (not surprisingly)

• genes

• development

• learning

Summary thoughts...

Things to think about with respect to experiments...

• Is “at chance” the right null hypothesis?

• If they “know it”, why don’t they nail it?

• going with the human cue

• going with past experience

• Very small sample size

• “Dogs” vs. “pet-dogs”

Using, knowing, understanding...

• ‘Using’ vs. ‘knowing’ vs. ‘understanding’ a cue...

• I ‘use’ the key to start the car.

• I ‘know’ when I turn the key the car will start

• I ‘understand’ the underlying ignition system of a car and how turning the key fits into that.

• ‘Using’ does not imply ‘knowing’ or ‘understanding’.

• When it doubt, observe don’t infer...

In comparison with wolves & chimps

• Difference in performance may reflect to a greater or lessor extent...

• motivational differences

• differing levels of anxiety with respect to close human contact

• Dogs may be better able to perform in close contact with humans (wave 1)

• Different breeds may be better able to use specific types of cues (wave 2)

Imprinting may play a critical role in setting the stage

• Scott and Fuller has shown that even minimal human exposure from 5 weeks on is sufficient to allow dogs to imprint on humans

• Imprinting in conjunction with reduced level of fear may

• bias dogs to attend to imprinted species (humans)

• be in an emotional state in which they can learn and perform

• Socialization: learning that is all about attending to cues associated with members of species on which they have imprinted.

• ‘Following’ as one of the things canids do, and dogs especially do.

In the end...

• Pet dogs, to a greater or lesser extent, seem to be able to use some human cues to guide their behavior. Duh...

• But it an emergent phenomena of other factors...

• imprinting

• later and less intense fear

• greater dependency (tendency to look to others...)

• Simple but reliable rules

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The Cognitive Dog Class 12: A little bit about statistics and alot about cue use.

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