Attention starts at fixation point and somehow ends up at cued location. Does it actually
move from one pt to next? When we shift our gaze, our pt of fixation sweeps across the
intervening space, attention might sweep across space too like spotlight beam metaphor.
Other possibilities are that attention might expand from fixation, growing to fill the whole
region from fixation spot to the cued location and then shrink to include just cued location =
zoom lens model of attention. Or when attention is withdrawn from fixation spot, it might
not move at all. It might simply melt away at that location and then reappear at cued
location. No correct metaphor. However evidence suggests tat attention is not moving from
pt to pt like spotlight would.
Visual search = lookin for a target in a display containing distract(or)ing elements, this
provides a closer approximation of actions of attention in real world.
What makes some search tasks easier than others. set size = # of items in a visual display.
One of the standard measure of the ease of search is to ask how much time (reaction time),
on average, is added for each item added to display. When target is absent it takes much
longer for subject to say it is not present than to say it is present. If we direct attention to
target as soon as display appears, regardless of set size, then we have an efficient search. If
we must examine each item in turn until we find target, then we have an inefficient search.
Different types of search tasks differ in efficiency
FEATURE SEARCHES ARE EFFICIENT/INEFFICIENT
Feature search = search for a target defined by a single attribute. If the target is salient
than it doesn’t matter wat itz set size of distractor is. We can process the feature of all items
at once, in parallel. so when we measure RT it not change w/set size like normally.
When the target and distracters in a visual search task contain same basic features =
inefficient search. serial self-terminating search = search from item to item, ending
when a target is found or all items checked. Thus on average one has to search through half
of the distractors before finding target.
IN REAL-WORLD SEARCHES, BASIC FEATURES GUIDE VISUAL SEARCH
Guided search = search in which attention can be restricted to a subset of possible items
on the basis of information about the target item’s basic features ie itz color
Conjunction search = search for a target defined by the presence of 2 or more attributes
ie red & small). This 2 feature conjunction searches tend to lie /b/ efficient features and
inefficient serial searches.