Ψ Cognitive Psychology Spring 2005 -Discussion Section-

Perception & Imagery

Cognitive functions Perception Imagery Perception Attention Memory Emotion Motivation Action Attention Memory Imagery Decision-making Reasoning, problem-solving Language

Perception What 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)

One final demo

Perception Our visual system makes assumptions in order to perceive the world around us. Studying perceptual illusions, we can get at the assumptions that our visual system makes

Why assumptions?

Perception Fundamental Reason 1: Duham-Quine Paradox time I

Perception Reason: 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

Really true?

Imagery Some demos...

The Problems: Too subjective, idiosyncratic Too introspective Too qualitative

High stakes... Stephen Kosslyn, John Lindsley Professor of Psychology at Harvard University

Mental scanning Kosslyn, Ball & Reiser (JExP, 1978)

The imagery debate(s) „No!“ „Yes!“ „Do mental representations of images retain the depictive properties of the image itself?“ Zenon Pylyshyn „No!“ „Yes!“ Stephen Kosslyn

The propositional perspective Pylyshyn: !?

The arguments Mental images represented by relations between symbols (language-like) Mental images represented in analogous form (vision-like) Distortions by labels, heuristics Demand characteristics Computer metaphor „Spatial equivalence“ „Perceptual equivalence“ „Transformational equivalence“ 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. 70s thinking. Artificial distinction

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: Perception: Classically bottom up: Imagery: Top down! Retina  LGN (Thalamus)  V1  V2  V4  IT  ?  …  ?  Frontal cortex Imagery: Top down! Basically the same systems: Frontal cortex  ?  …  ?  IT  V4  V2  V1.

Shepard The grand old man of cognitive psychology

Shepard & Metzler (Science, 1971) 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!)

QALMRI Q: A L M R I P

Exam review Purpose of early exam? To scare you into studying. You can´t wing it.

Exam review Format: 6 essay questions. All of the themes are represented (Intro, Attention, Perception1, Perception2, Imagery). 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.

Key concepts to know (and understand) Early vs. late selection Automated vs. controlled processing Stroop effect Visual search, Popout Attenuated thresholds Cocktail party phenomenon Shadowing Response selection Change blindness

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.

Key concepts to know Gestalt rules of perception Bottom-up and top-down processing Mental representation Assumptions/Illusion connection Principles of Object, Depth, Motion perception Principles of Categorization Geons Failures of perception: Different Agnosias

Imagery: *Activation of a mental representation from memory. In ABSENCE of a stimulus. *Paradigmatic case of TOP-DOWN processing. *Debate between Pylyshyn and Kosslyn whether mental representation in imagery analog or propositional. (Since 30+ years!) *Most brain areas active in perception are also active in imagery.

Key concepts to know Analog vs. propositional representation Imagery Debate Kosslyn vs. Pylyshyn a) Models b) Arguments c) Behavioral Evidence d) Neuroscience Evidence Kosslyn: Free lunch implication Mental rotation

Good luck!