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Ben-Gurion University of the Negev
Dept. of Brain and Cognitive Sciences
NEURAL DATA-ANALYSIS
WORKSHOP
REACTION TIMES (RT)
 The basic premise underlying the use of RT in cognitive
psychology is the assumption that cognitive operations
take a certain and measurable amount of time .
 In addition, it is assumed that additional mental
processes add (more or less) linearly. If this is the case,
increased RT reflect additional mental processes.
 Let us assume for the time being that this is a
reasonable framework. Then, it is highly useful to have
a program that allows you to quickly collect RT data
THE VISUAL SEARCH PARADIGM
 In the visual search task participants are asked to
report the presence or absence of a target stimulus
among various numbers of distracter stimuli.
 If the distracter stimuli differ by a single feature you
usually find the “pop-out” effect: the RT to detect the
target is independent of the number of distracters.
 Conversely, if more than one stimulus dimension has to
be considered (conjunction search), you typically find a
linear relationship between RT and the number of
distracters.
 This pattern of results suggests the existence of feature
primitives, fundamental dimensions that organize and
govern human perception.
VISUAL SEARCH
Feature search
Conjunction search
O
X
X
O
X
X
O
X
O
O
O
O
X
O
O
O
O
O
O
X
O
O
O
O
X
O
O
X
VISUAL SEARCH
DEMO OF THE PROJECT
Demo in MATLAB
EXPECTED RESULTS
Correctly Identified the Presence of Target
2.6
Mean Reaction Time (sec)
2.4
Pop Out
Conjunction
2.2
2
1.8
1.6
1.4
1.2
1
4
6
8
10
Set Size
12
14
16
EXPECTED RESULTS
Correctly Identified the Absence of Target
4
Pop Out
Conjunction
Mean Reaction Time (sec)
3.5
3
2.5
2
1.5
1
4
6
8
10
Set Size
12
14
16