Cognitive Processes PSY 334 Chapter 4 – Perception-Based Knowledge Representation

Dual-Code Theory  The mind operates upon internal representations of knowledge.  How is visual information (imagery) represented in memory?  Paivio’s Dual-Code Theory – memory is better if we encode information visually and verbally. Separate representations are maintained for verbal and visual information.

Evidence for Dual Codes  Santa compared linear and spatial arrays of: Three geometric objects Three names of geometric objects  Subjects were asked whether the arrays contained the same objects or names.  Subjects were faster when shapes were in the same spatial arrangement but faster when words were linear.

Evidence From Brain Imaging  Subjects were asked to mentally rehearse: A word jingle Navigating their neighborhood  Increased blood flow occurred in different areas of the brain, depending upon the task.  The same brain areas were active as when actually speaking or seeing.

No Homunculus  Homunculus -- the idea that there are “pictures in the head” implies someone to look at those pictures. Both images and percepts are represented topographically in the brain, but there is no homunculus to view them.  Kosslyn -- the same processes are used to view mental images and external percepts.

Mental Rotation  Shepard – two-dimensional and three- dimensional mental images are rotated in the same way as actual objects. The more an object is rotated, the longer it takes to respond in a same/different task.  Georgopoulos et al. – measured neurons firing in monkey brains when moving a handle. Intermediate cells fire showing rotation.

Image Scanning  Brooks – subjects scanned imagined diagrams (like letter F) and noted outside corners, or sentences noting nouns. Respond by saying “yes” or “no” Tap left hand for “yes,” right hand for “no” Point to Y or N on a sheet  Scanning a sheet for Y’s & N’s conflicted with scanning the mental image. Conflict is spatial not visual.

Comparing Visual Quantities  Time to make a judgment decreases as the difference in size between objects increases. The smaller the difference the longer it takes to make a judgment.  Which is larger: moose or roach, wolf or lion?  The same pattern emerges when asked to judge actual differences, line lengths.

Two Types of Imagery  Images involving visual properties (what) -- impaired with temporal damage.  Images involving spatial properties (where) – impaired with parietal damage.  Bilateral temporal lobe damage: Difficulty judging color, size, shape. No deficit in mental rotation, image or letter scanning, judgment of relative positions.

Are Images Like Perception?  A series of experiments to compare perception and imagery: Imagining transformations of mental images vs perceived stimuli. Ponzo illusions occurs with imagery. Difficulty with reversible figures – depends on instructions, harder.  MRI plots show same brain activity.

Cognitive Maps  Two kinds of maps: Route map – indicates places and turns, but not all landmarks. Survey map – shows all relevant portions of space, not just route.  Adults produce survey maps, kids produce route maps.  Survey maps more versatile.

Map Distortions  Which is farther east: San Diego or Reno?  People make wrong guesses because they reason from the positions of the states, not cities.  Relative positions of larger areas are compared, not details – hierarchical chunking.

Translating Verbal Descriptions  Subjects were asked to read passages, rotate themselves and make judgments: Fastest when making above-below judgments, slower with right-left.  Verbal directions (survey or route) are as good as using actual maps.

Remembering Serial Position  Serial position – what comes first and what comes later in a list.  Anchoring – first items are better remembered in sequences.  Hierarchical encoding helps serial recall: Alphabet song

Hierarchical Encoding of Serial Order Information  Long sequences are remembered using hierarchical chunks, just as maps are: Alphabet song Spacing of letters separates them into subsequences (chunks).

Baddeley’s Working Memory  Imagery is accomplished in working memory.  Two parts correspond to dual-codes: Visuospatial sketchpad – visual info Phonological loop – verbal info  Central executive – coordinates the slave systems (sketchpad & loop)

Parts of the Phonological Loop  Articulatory loop – inner voice that rehearses verbal information Activates Broca’s area of the brain  Phonological store – an inner ear that stores the inner voice and stores it in phonological form. Activates parietal-temporal areas of brain