PSYCH 240 LEC 8 (VISUAL IMAGERY)

Depictive codes

• Picture-like

• Not as much power ad propositional

• All parts must correspond to things being represented in pictures

Propositional codes

• Presenting propositions in the world

  • language-like

  • powerful bc can create any proposition representation

  • includes syntactic parts not corresponded to the object (“the” in globe on the desk)

Evidence for depictive codes: interference effects

• Perform two tasks simultaneously, if they interfere then they must require the same mental system

  • visual and auditory perception + imagery are shared

  • experiment: bc of multitasking the tasks

Evidence for depictive codes: scanning effects

• Longer distance of landmarks in drawing

• Takes longer to scan from one landmark to another

Evidence for depictive codes: zooming

• zoom in and include flies to make it more characteristically small

• Respond slower when near larger object

• Respond faster when near small object

  • Ask abt the rabbit ears going up or down

Evidence for depictive codes: transforming/mental rotation

• Results:

  • 2D + 3D mental rotation there is a linear relationship

  • increase in rotation angles , increases reaction time

Demand characteristics

• Subject scan image bc they infer researcher’s wants them to

• Prevention:

  • Experimenters expect a certain set of results and causes biases so hiring new ones and to be more unbiased

Differences between imagery and perception

Perceptions

• Metric qualities like length and distance @ high resolution that images don’t have

• Better at extracting partial info from perception

  • Parallelogram in Star of David

Images

• Hard to imagine

  • i.e. a complicated image of a bisected rectangle with diagonal lines

Imagery vs Perception: metric qualities

• Supports perception with high-res metric qualities (exact length, distance, and angles)

• Mental images are:

  • Hard to imagine bisected rectangle with diagonal lines without seeing it

    
    

Imagery vs Perception: part-whole relationships

• Supports perception

  • Seeing parallelogram in perceived Star of David

• Mental image:

  • Struggle to discover them when inspecting

Imagery vs Perception: ambiguous figures

• Supports perception

  • Figure of duck + rabbit is ambiguous

• Imagery:

  • What else could that figure have been? Cannot flip or reinterpret in mind

Compromise theory

• Proposed by Kosslyn

  • Basic Code is propositional (stored in LTM)

  • Propositional code is used to create depictive image

  • Depictive image can be scanned + zoomed

    • i.e. nonbinary code on DVD then interpreted by the DVD player → turn to depictive representation

  • Could be due to top-down processing in visual cortex

Shared brain areas for imagery & perception

Generating image using Top/Down processing to build visual representation in visual cortex → then execute

• grid letters to support how visual imagery functions in the brain

Effects of image complexity

Increase in strokes/visual segment quantity, longer time to react if the X lands on the cube bc longer time to generate mental image of letters in pixel form

Evidence that image parts are generated sequentially

• Ordered Image Construction data suggest more segments = longer time to react

  • i.e. we are writing letter in our mind analogous to write it IRL

Damage to motor cortex impairs imagery

R Lesion to motor projection area

• LS damage to show image perception + writing image of capital F vs

L Lesion to motor projection area