Cognitive ProcessesPSY 334

Chapter 2 – Perception

Concerns about Cognitive Models

Relevance – do lab-task processes operate in the same manner in real life?

Sufficiency – can simple theories explain complex processes? Cognitive architectures

Necessity – does the mind actually work as described by specific theories? Cognitive neuroscience

Other Approaches to Cognitive Psychology Connectionism (neural net models) –

can higher level functions be accomplished by connected neurons? Parallel distributed processing (PDP) --

Rumelhart & McClelland Situated cognition – the ecological

approach Gibson’s affordances Do we explain cognition in terms of the

external world or internal mind?

Cognitive Neuroscience

Pages 16-31 review basic concepts about the brain. If you have not taken PSY 210 and find

this material confusing, come see me. New methods permit study of normal

human functioning in more complex tasks: EEG Imaging techniques – PET & fMRI

Visual Perception

Distal stimulus -- tree Proximal stimulus – image of tree on

retina Percept – interpretation of proximal

stimulus as a tree Size and color constancy

Information Coding

On-off cells in LGN feed into edge and bar detectors in the visual cortex.

Edge detectors – respond positively to light on one side of a line, negatively on the other side of the line.

Bar detectors – responds maximally to a bar of light covering its center.

Marr

Depth cues (texture gradient, stereopsis) – where are edges in space?

How are visual cues combined to form an image with depth? 2-1/2 D sketch – identifies where visual

features are in relation to observer. 3-D model – refers to the representation of

the objects in a scene.

Pattern Recognition

Classification and recognition occurs through processes of pattern recognition.

Bottom-up processes – feature detection Top-down processes -- conceptually

driven processing

Object Recognition

Two stages: Early phase – shapes and objects are

extracted from background. Later phase – shapes and objects are

categorized, recognized, named.

Disruptions of Perception

Visual agnosias – impairment of ability to recognize objects. Demonstrate that shape extraction and shape

recognition are separate processes. Apperceptive agnosia (lateral) – problems with

early processing (shape extraction). Associative agnosia (bilateral) – problems with

later processing (recognition). Prosopagnosia – visual agnosia for faces.

Gestalt Priniciples

Wertheimer, Koffka, Kohler. Form perception – segregation of a

display into objects and background. Principles of perceptual organization

allow us to see “wholes” (gestalts) formed of parts. We do not recognize objects by identifying

individual features.

Five Principles

Proximity Similarity Good continuation Closure Common fate

Elements that move together group together.

These will be on the midterm.

Examples

• Gestalt principles of organization• Reversible figures• Stuart Anstis demos:

http://psy.ucsd.edu/~sanstis/SACamov.html

http://psy.ucsd.edu/~sanstis/motion.html

Law of Pragnanz

Of all the possible interpretations, we will select the one that yields the simplest or most stable form.

Simple, symmetrical forms are seen more easily.

In compound letters, the larger figure dominates the smaller ones.