This document describes a ZAPS experiment on visual search that tested how quickly participants could find a target object among arrays of distractors. It involved three conditions that varied the presence/absence of the target, number of objects, and type of search (feature vs conjunction). Reaction times were fastest for feature searches of a single attribute and slowest for conjunction searches combining two attributes, as predicted by feature integration theory. The experiment demonstrated how selective attention allows for efficient detection of salient stimuli but requires focused attention for more complex searches.

1. ZAPS experiments: Visual Search
ZAPS experiments: Visual SearchZAPS experiments: Visual Search INTRODUCTIONYou are
meeting a friend in the main concourse of Grand Central Terminal in New York City, in
which thousands of tourists and people getting on and off trains pass through every day.
Because of the hordes of people, you worry about being able to find your friend. However,
he has promised to wear a bright red coat so he will be easier to spot.Psychologist Donald
Broadbent developed filter theory in 1958 to explain the selective nature of our attention,
or conscious awareness. Your friend’s plan cleverly takes advantage of our selective
attention abilities. Your brain is continually bombarded with visual and other sensory
information than it can be conscious of at once. Your mind copes by automatically
screening, or filtering, incoming sensory information to let in only what is most
important.In the main concourse of Grand Central, your friend’s red coat will serve as
a salient feature that your mind can use to selectively ignore surrounding distractors (in
this case, the hundreds of other people in the concourse). If you correctly apply your
selective attention filter, you should be able to ignore all of the inputs you’re trying to block
(anyone not wearing red) and focus specifically on your target: the red coat.Your friend’s
plan was perfect, right? But what if he arrives at the exact time as a throng of visiting St.
Louis Cardinals fans (all wearing Cardinals red, of course) who are passing through the
concourse on their way to Yankee Stadium, in which the Cardinals will be playing the New
York Yankees?ORDER COMPREHENSIVE SOLUTION PAPERS ON ZAPS experiments: Visual
SearchThe red-clad Cardinals fans will make your search a lot more difficult, since their red
jerseys will become distractors. They might make it through your brain’s selective filter and
become stimuli that your mind attends to (focuses attention on) even though they are not
your target (your friend).Selective attention filters enable us to make more automatic
decisions about the stimuli around us, including which items to pay attention to during
a visual search. In this ZAPS lab, you will participate in a classic psychological experiment
that uses visual search tasks to explore fundamental processes of visual perception and
attention. These tasks (also called feature search tasks) stem from research on attention by
psychologist Anne Treisman. Exploring them should help you understand one of the ways
our attention to specific features functions.InstructionsAs you learned in the Introduction,
an object of interest is more or less salient in a field of other objects. This depends on
prominent visual features including color, shape, size, and movement. The purpose of this
ZAPS lab is to see how such features, in addition to the number of objects in the visual field
(called distractors), influence how quickly we can find a target object.Your task is to decide,

2. as quickly as possible, whether a particular target object—in this case, a blue circle—is
present in an array of other shapes. If the blue circle is present, click “yes.” If the blue circle
is not present, click “no.” For example, you would click “yes” if the following array was
presented because a blue circle is present.In this experiment, you need to quickly decide
whether your target, a(n) _________, is present in each array of objects.Click or tap a choice to
answer the question.orange squareorange circleblue circleblue squareCorrect!This answer
is correct.You answered the question correctly on your first attempt, so your grade for the
question is 100%. Experience Data IntroductionYou completed the various trials in three
different conditions, measuring three independent variables. The first being that sometimes
the blue circle was present, other times it was not. The second independent variable was
that sometimes only 4 objects appeared in the array, other times 16, and then as much as
64. The third independent variable was the nature of the distractor objects.The first set of
trials asked you to find the blue circle amidst orange squares and orange circles. This is an
example of a feature search task because you were able to search for a single feature
(“blueness”) that distinguished the target from all the distractors.In contrast, the second set
of trials asked you to find the blue circle amidst blue squares and orange circles. This is an
example of a conjunction search task because no one feature distinguished the target from
the distractors (some distractors were blue and some were circles) and you were forced to
search for a conjunction of two features—color (blue) and shape (circle).The key question is
how much your reaction time—how quickly you decided whether or not the blue circle was
present—was influenced by these three variables: 1) the presence or absence of the blue
circle; 2) the complexity of the array; and 3) the type of search task. For a task that is
relatively easy, we expect to see relatively quick reaction times.On the graph that follows,
you will see reaction time (in milliseconds) plotted along the y- axis, and the number of
objects in each array (4, 16, or 64) plotted on the x- axis. Different lines will represent the
presence or absence of the blue circle (“yes” and “no” trials) and the type of search task
(Feature Search or Conjunction Search).Based on your experience during the experiment,
which combination of variables do you think resulted in the quickest reaction time? The
slowest reaction time? Why? You will initially receive full credit for any answer, but your
instructor may review your response later. YOUR DATA· Graph· Table· Raw
Data DISCUSSIONAccording to Anne Treisman’s feature integration theory about attention
and recognition, we begin a visual search by automatically indentifying “primitive” (or
simple) features—such as color, shape, size, and movement—within an environment. She
further proposed that our mind uses separate systems to analyze the different visual
features of objects at the same time. This ability is called parallel processing. We can attend
selectively to one feature by effectively blocking the further processing of the others
(Treisman & Glade, 1980). Sample trial from the feature search part of the
Experience.Sample trial from the conjunction search part of the Experience. In the first set
of trials—the feature search part of the Experience—you were asked to search for a single,
simple feature, the color blue. Searching for a single stimulus, such as the blue circle (or
your friend’s red coat in the Introduction), happens fast and automatically through what is
known as pre-attentive processing. We do not need to deliberately focus to process this
sensory information. The target was so salient that it seemed to “pop out” immediately,

3. regardless of the number of distractors.In the second set of trials—the conjunction
search part of the Experience—your task was more complicated. You were asked to find the
blue circle amidst blue squares and orange circles. It is a conjunction search because the
stimulus you are looking for is made up of two simple features (color and shape) that are
conjoined. When searching for two features, you need to look at the stimuli one at a time
since your mind is not able to automatically process the tasks. Not only does it take longer,
it also requires more attention. Because you had to deliberately focus, it is highly likely that
your reaction times were higher for these trials.Our ability to filter and selectively attend to
sensory information doesn’t only affect our conscious awareness of visual information. Our
auditory attention also allows us to listen selectively. In fact, the mind has many means of
coping with the influx of information it receives—and most of the time, we are unaware
they are occurring.How might you be able to find your friend in the red coat at Grand
Central Terminal even if he is amidst a huge crowd of other people wearing red? You will
initially receive full credit for any answer, but your instructor may review your response
later. LEARNING CHECKAnswer the following questions to complete this ZAPS activity. Your
performance in this section accounts for 10% of your grade.Imagine you have been asked to
find the following object pictured on the left in the accompanying array on the right.What
type of search do you think this would be?Click or tap a choice to answer the
question.conjunction search feature searchImagine you have been asked to find the
following object pictured on the left in the accompanying array on the right.What type of
search do you think this would be?Click or tap a choice to answer the question.feature
search conjunction searchBased on the ideas presented in this ZAPS lab, which of the
following tasks would you expect to be the most difficult visual search for someone to
complete?Click or tap a choice to answer the question.finding two black socks in a laundry
basket otherwise filled with white socksfinding the teacher in a preschool classroom amidst
a group of 4-year-oldsfinding the 3 of spades in a deck of 52 playing cards that vary by suit
(hearts, diamonds, clubs, and spades) and number (aces, numbers 2-10, jacks, queens,
kings)finding the green M&Ms in a bag of M&MsZAPS experiments: Visual Search