Lecture 6 Visual Search

Question 1

visual search

Answer 1

finding a target in space (feature integration theory); finding a target in a time series (rapid serial visual search; “repetition blindness”; “attentional blink”)

Question 2

feature search

Answer 2

type of search; looking for an odd man out (look for a uniquely colored object); easy; fast (300 ms); parallel (0-10 ms/item); “preattentive”

does not require attention –> efficient (evidence for feature integration theory)

Question 3

conjunction search

Answer 3

type of search; looking for a combination of features (e.g., T among Ls; red vertical among green vertical and red horizontal); hard; slower; sequential; attentive

requires attention –> inefficient (evidence for feature integration theory)

Question 4

feature integration theory

Answer 4

Anne Treisman; a visual display is coded by two types of maps: feature maps and master map of locations; feature maps and location map are insufficient – need some way of locating features and binding appropriate features together –> attention does this by moving within the location map and selects whatever features are linked to that location (or object)

Question 5

feature maps

Answer 5

contain info about the presence of a feature anywhere in the field; activity tells us what is out there; have no info about where it is located and what other features the object has

Question 6

master map of location

Answer 6

contains info about where features are; has no info about which features are located where

Question 7

search asymmetry

Answer 7

evidence for feature integration theory

hypothesis: simple features are detected because they produce unique activation on a feature map
prediction: the absence of a feature should be harder to detect than the presence of a feature

Question 8

illusory conjunction

Answer 8

evidence for feature integration theory

hypothesis: simple features are bound to a location by the operation of focused attention
prediction: without attention, features may be incorrectly bound to locations

example:

• primary task: recognize digits at left and right
• secondary task: report letters in the middle
• presented with: [8 greenT orangeL purpleD 3] –> was there an orange D, purple d, or green D?
• subjects sometimes think they saw an orange or green D

Question 9

balint syndrome

Answer 9

part of illusory conjunction; patients have brain damage to both sides of parietal lobe; see only one object at a time; also known as “simultagnosia”

patient RM: no difficulty with feature search, poor at conjunction search

• shown two colored letters (red T, yellow X)
• rarely commit color or letter intrusions (green T, red O)
• high percentage of illusory conjunction (yellow T, red X)

Question 10

neurophysiological evidence for FIT

Answer 10

different brain regions code different features separately; attention binds features together

Question 11

rapid serial visual presentation (RSVP)

Answer 11

searching for a pre-specified target is easy –> visual perception is fast; recognizing a target AFTER the series has been presented is difficult –> visual memory is limited

Question 12

What where the Visual Search lab results?

Answer 12

a

Question 13

repetition blindness

Answer 13

RSVP phenomena; failure to detect repetitions of visual stimuli in lists presented in RSVP; occurs even when words differ in case or locations

Question 14

attentional blink

Answer 14

RSVP phenomena; when one target is detected, people often fail to detect a second (different) target within the next 200-500ms