PSY 3217 Ch. 11: Visual Knowledge

visual knowledge

 concerns what we know about how objects and scenes look and how they are arranged in space

mental imagery

 representing perceptual information when the relevant stimulus is not physically present

self report

ask ppl to describe vividness, clarity, or detail. Reports can be influenced by vocab, expectations, and interpretation.

behavior

measure reaction time, accuracy, interference, or errors. Lets us infer what operations may be taking place during imagery.

brain evidence

use neuroimaging, lesions, or brain stimulation to examine which neural systems contribute to imagery.

chronometric methods

•  use response time to infer the mental operations involved in imagery

• If an imagined representation preserves spatial relationships, then larger imagine distances or transformations require more time.

image scanning

how long does it take to shift attention from one imagined location to another

mental rotation

how long does it take to transform an object into a different imagined orientation

Kosslyn, Ball, Reiser study

• Participants memorized a map w landmarks, formed mental image and focused on one, second landmark was named, and aprticipants scanned to it. Scanning time increased as the distance between landmarks increased.

• Telling us we keep spatial information to make accurate estimates

Shepard and Metzler study

• Participants viewed pairs of 3-dimensional block figures

• Some pairs showed the same object at diff orientations; others showed diff objects

• Reaction time rose almost linearly as the angular difference between the objects increased

demand characteristics

Cues that reveal what participants think the experimenter expects

• Participants might intentionally respond more slowly for larger imagined distances or rotations

• Means that no single chronometric study can settle the Q of how imagery is represented

• Researchers look for converging evidence from perception, brain measures, neuropsych, and additional behavioral tasks

Perception

 driven strongly by external sensory input. Info begins w/ stimulation of the visual system

overlap of perception and imagery

both can represent shape, color, location orientation, and spatial relations. Also interfere w. One another (visuospatial sketchpad)

imagery

 generated from memory and knowledge w/o the object being physically present

frontal systems

control and generation of image

parietal systems

 spatial information (big or small)

ventral visual areas

object and form (shape)

visual cortex

perceptual detail (traits, color of fur?)

O’Craven and Kanwisher study

• Participants either viewed or imagined faces and places while undergoing fMRI

• Face imagery selectively activated the fusiform face area

• Place imagery selectively activated a region associated w/ place perception

• Perception generally produced stronger activity than imagery, content-specific pattern overlapped

Content of a mental image matters for which visual regions become active

hyperphantasia

some people report highly vivid, almost perception-like imagery.

Mental scenes feel unusually detailed. Highlights importance of measuring both subjective experience and objective performance

aphantasia

others report weak or absent voluntary visual imagery.

Still know what objects look like. Visual knowledge and the conscious experience of imagery can be partly dissociated.