ΨΨCognitive Psychology

Winter 2004

-Discussion Section-

Perception

&

Imagery

Cognitive functions• Perception

• Memory• Attention

• Decision-making• Reasoning, problem-solving

• Imagery

• Language

Emotion

Motivation

Action

• Perception

• Imagery

PerceptionPerception, Imagery, Shepard & Metzler and Review. There is no way that I can go in any detail in Perception.

So let´s just review the most important principle.

PerceptionWhat we perceive is NOT a exact copy of the external world, it is a selective RECONSTRUCTION.

It is a MENTAL REPRESENTATION.

(of aspects of the external world)

Implications:

1) Things that we perceive might not be actually present in the environment.

2) Things that are actually present in the environment might not be perceived (see: Attention examples of last time).

3) Changes in the environment might not result in changes in perception.

4) Changes in perception might not result from changes in the environment.

4 fundamental non-correspondences

Perception

4) Shepards tables

1) Kanisza triangle

Perception4) Motion-induced blindness

http://www.keck.ucsf.edu/~yoram/mib.html

Perception

3) Color-constancy

PerceptionFundamental Reason 1: Duham-Quine Paradox

time

I

PerceptionReason: Limited Sampling. Inference with limited information. „Aliasing“. Needs assumptions to disambiguate.

0 10 0 7 6 1 9 0 0 10 0 7 6 1 9 0

Perception1 Physical Stimulus 2 Filter1 (Static) 3 Filter2 (Variable) 4 Filter3 (Variable) 5 Mental representation 6 Filter4 7 Mental representation 8 Filter5 9 Action.

1) e.g. Light

2) e.g. Photoreceptors

3) e.g. Eye movements

4) ATTENTION!

5) Commonly refered to as PERCEPTION!

6) ATTENTION!

7) MEMORY!

8) Action selection

9) e.g. Catching a ball

Perception

On the other hand, this allows us to study the assumptions, the PROCESSING by looking at illusions and how people perceive them.

PerceptionA huge brain machinery is devoted to process visual information alone. 30% of the brain. At least. Together with other perceptual information: Easily 50%. To allow us to act efficiently on impoverished input.

Imagery

Some demos...

The Problems:

•Too introspective•Too qualitative

•Too subjective, idiosyncratic

High stakes...

Stephen Kosslyn, John Lindsley Professor of Psychology at Harvard University

Mental scanningKosslyn, Ball & Reiser (JExP, 1978)

The imagery debate(s)„Do mental representations of images retain the depictive properties of the image itself?“

„Yes!“

Stephen Kosslyn Zenon Pylyshyn

„No!“

The propositional perspective

!?

Pylyshyn:

The argumentsMental images represented by

relations between symbols

(language-like)

•Distortions by labels, heuristics

•Demand characteristics

•Computer metaphor

Mental images represented in analogous form

(vision-like)

•Moot point 1: Anderson (PsycRev,1978): RT not diagnostic due to Representation/Process tradeoffs, emulating both.

•Moot point 2: Representation = Process. Need to look at neurophysiology for the CODE.

•„Spatial equivalence“

•„Perceptual equivalence“

•„Transformational equivalence“

Resolution 1 - Paradigm„Visual mental imagery activates the same areas as visual perception“

(Kosslyn, et al., JCogNeuro, 1993)

Resolution 1 – Paradigm

„Visual mental imagery activates the same areas

as visual perception“

(Kosslyn et al., JCogNeuro, 1993)

Resolution 2

„Visual mental imagery activates many visual areas, INCLUDING V1“

(Kosslyn et al., Nature 1995; Kosslyn et al., Science 1999)

Current state:

•Imagery: Top down!

•Basically the same systems:Frontal cortex ? … ? IT V4 V2 V1.

•Perception: Classically bottom up:Retina LGN (Thalamus) V1 V2 V4 IT ? … ? Frontal cortex

Shepard

The grand old man of psychology

Mental rotation•Shepard & Metzler (Science, 1971)

Mental rotation

•Issue?The nature of mental representations? Can they be manipulated like one would expect from the laws of physics? Does the internal world follow the principles of the external world (it doesn´t have to!)

Exam review

•Purpose?

To scare you into studying. You can´t wing it.

Exam review

•Ground rules:

No cheating. You WILL regret it!

Exam review•Format:

•6 essay questions. One from each field (Intro, Reason, Attention, Perception1, Perception2, Imagery). Do 5 of them.

•10 Multiple Choice Questions.

•1 Bonus Question.

•Attention:*Explains many things and nothing. A theoretical fudge factor. Equals “trophic factors”.

*There are many models, all of them fail to capture essentials of the phenomenon. Prominent: Treismans Attenuation theory, Broadbents early selection theory.

*Most useful to think of as a variable filter that generates mental representations for action selection.*There are processes that are automatic, others need attentional resources. They reflect a tradeoff.

*Attention involved in many phenomena: Visual Search, Popout, Change blindness, etc.

•Perception:*Perception is the formation of a mental representation of the environment.

*This representation is NOT isomorphic, but subject to many correspondence errors. *To overcome the inherent ambiguity in sensory data, the brain makes assumptions about the world. (Learnt in phylogeny, ontogeny). Like Gestalt rules. * These assumptions can be uncovered by research with visual illusions.

•Imagery:

*Activation of a mental representation from memory. In ABSENCE of a stimulus.

*Most brain areas active in perception are also active in imagery.

*Paradigmatic case of TOP-DOWN processing.

*Debate between Pylyshyn and Kosslyn whether mental representation in imagery analog or propositional. (Since 30+ years!)

•Reasoning:* There are two ways of reasoning, deductive (Rule Particular instance) and inductive reasoning (Data Rule). They both have advantages and disadvantages.

* People are subject to many biases in reasoning, most particularly the confirmation bias, which usually affects them in hypothesis testing. (Elicited by Wason selection task). Also common: Baserate neglect.

* People should try to falsify, not to verify their hypotheses.