The more general questions 
about the role of attention in 
perception are these: What, if 
anything, do we perceive prior 
to attention, and what role does 
attention play once it does 
enter into the chain of events 
culminating in our perception 
and recognition of objects? 
Given the welter of stimuli 
with which we are bombarded 
every moment of our lives, one 
would think that some 
mechanism would be necessary 
to allow us to attend selectively 
to certain items and thereby to 
remember them as well.

    To try to answer questions 
about the role of attention, a 
favored experimental paradigm 
has been to present subjects 
with an array of many 
elements, such as the "pop out" 
figures discussed earlier, and 
then try to ascertain how they 
perceive the pattern. In the 
paradigm illustrated there the 
question concerned the 
segregation of one region from 
the rest of the array, often 
called "texture segregation." 
The presentation is only 
milliseconds long and is often 
followed by a patterned "mask," 
which stops further processing. 
In a similar kind of 
experiment, only one element 
in the array differs from the 
others, which are typically 
identical. Here the task is to 
search for that element. If that 
item differs with regard to some 
feature, such as color or line 
orientation, the search for the 
target item is easy, and it is said 
to "pop out."