Visual Search Task - Divided Attention

Technical Manual

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond

Created: June 19, 2017

Last Modified: October 15, 2026 by K. Borchert (katjab@millisecond.com), Millisecond

Background

This script implements a basic visual search paradigm based on Motter & Simoni (2008).

References

Motter,B.C., & Simoni, D.A. (2008). Changes in the functional visual field during search with and without eye movements. Vision Research 48 (2008) 2382–2393.

Duration

25 minutes

Description

Participants are asked to check letter arrays of green and red L's and T's (in 6 different spatial rotations) of varying array sizes (6, 12, 24, 48) for a target letter. The target letter shares one feature with each distractor letter ("conjunction style search array"). For example, if the target letter is a red L, the distractor letters are red T's and green L's. Half the arrays contain the target.

Procedure

Practice: Default

- 24 practice trials (6 per target category, e.g. 'green L', order is randomized)
- each possible target is used once per target category - random selection)
- 2 different array sizes per target category (4 stims vs. 16 stims), random selection
- half the trials (12) have the target present (order of 'target present' vs. 'target absent' randomized)
- provides performance feedback

Test: Default

2 target colors (green vs. red) x 2 target letters (L vs. T) x 4 array sizes (6, 12, 24, 48) x 2 target condition (present vs. absent)
x 6 reps = 192 trials,
tested in a full, mixed design

- the 4 target categories (color x letter) are selected in random order
- in each of the 4 target conditions (color x letter, e.g. 'green L'):
- equal frequency of the 4 possible array sizes (array size is randomly determined)
- half the targets are present, half the targets are absent (randomly selected)
=> balanced across the 4 different set sizes (6 targets present/6 targets absent for each of the 4 set sizes)
Motter & Simoni (2008) ran sessions of 240 trials.

- Target Selection:
- The target stimulus is selected randomly from the 6 possible rotations (see under STIMULI) for the given target condition)
- each rotation is selected equally often
=> each target rotation is run 8 times per target condition

- Distractor Selection:
- half the distractors are selected from the opposite color (but same letter)
-> the appropriate item numbers are selected randomly without replacement (repetitions are possible, once all 6 possible stims were selected)
- the remaining distractors are selected from the same color (but different letter)
-> the appropriate item numbers are selected randomly without replacement (repetitions are possible, once all 6 possible stims were selected)

- Stim Locations:
- 48 possible stim locations (7x7 matrix, with fixation cross in the center)
- stim locations are randomly (without replacement) assigned to each of the stims (including target)
- stim locations reset before each new trial

Canvas:
By default, the canvas (=part of the screen used by this script) is the biggest square (width = height) that can be
established on the current monitor. The canvas can be further manipulated by explicitly forcing
a specific canvas size and/or by forcing a specific windowsize (see section DEFAULTS for more info)

Trial Sequence:

Fixation Cross (until Spacebar press) -> Cue (default: 1000ms)->Array (max: 7000ms)

Stimuli

provided by Millisecond - can be edited under section Editable Stimuli

each target category (green L, red L, green T, red T) can be represented by 1 of 6 orientations:
the letter was rotated 6 times by increments of 60deg

Instructions

Instructions are not original to the task. They are provided by Millisecond
as htm/html pages and can be edited by changing the provided htm/html files.
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).

Summary Data

File Name: visualsearch_letter_et_summary*.iqdat

Data Fields

Name	Description
startDate	Date the session was run
startTime	Time the session was run
subjectId	Participant ID
groupId	Group number
sessionId	Session number
inquisit.version	Inquisit version number
computer.platform	Device platform: win \| mac \|ios \| android
computer.touch	0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities
computer.hasKeyboard	0 = no external keyboard detected; 1 = external keyboard detected
elapsedTime	Session duration in ms
completed	0 = Test was not completed 1 = Test was completed
canvasHeightMM	The height of the screen canvas used for the script in mm
canvasWidthMM	The width of the screen canvas used for the script in mm
accOverall	Overall proportion correct (across all test trials)
meanRT	Mean latency (in ms) across all correct test trials
accTargetPresent6	Proportion correct of trials with 6 stimuli where the target is present
rtTargetPresent6	Mean correct latency (in ms) of trials with 6 stimuli where the target is present
accTargetAbsent6	Proportion correct of trials with 6 stimuli where the target is absent
rtTargetAbsent6	Mean correct latency (in ms) of trials with 6 stimuli where the target is absent
accTargetPresent12	Proportion correct of trials with 12 stimuli where the target is present
rtTargetPresent612	Mean correct latency (in ms) of trials with 12 stimuli where the target is present
accTargetAbsent12	Proportion correct of trials with 12 stimuli where the target is absent
rtTargetAbsent12	Mean correct latency (in ms) of trials with 12 stimuli where the target is absent
accTargetPresent24	Proportion correct of trials with 24 stimuli where the target is present
rtTargetPresent24	Mean correct latency (in ms) of trials with 24 stimuli where the target is present
accTargetAbsent24	Proportion correct of trials with 24 stimuli where the target is absent
rtTargetAbsent24	Mean correct latency (in ms) of trials with 24 stimuli where the target is absent
accTargetPresent48	Proportion correct of trials with 48 stimuli where the target is present
rtTargetPresent48	Mean correct latency (in ms) of trials with 48 stimul]i where the target is present
accTargetAbsent48	Proportion correct of trials with 48 stimuli where the target is absent
rtTargetAbsent48	Mean correct latency (in ms) of trials with 48 stimuli where the target is absent

Raw Data

File Name: visualsearch_letters_raw*.iqdat

Data Fields

Name	Description
date	Date the session was run
time	Time the session was run
subject	Participant ID
group	Group number
session	Session number
build	Inquisit version number
computer.platform	Device platform: win \| mac \|ios \| android
computer.touch	0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities
computer.hasKeyboard	0 = no external keyboard detected; 1 = external keyboard detected
canvasHeightMM	The height of the screen canvas used for the script in mm
canvasWidthMM	The width of the screen canvas used for the script in mm
blockCode	Name of the current block
blockNum	Number of the current block
trialCode	Name of the current trial
trialNum	Number of the current trial
phase	Current phase: "practice" vs. "test"
trialCount	TrialCounter per block
arraySize	Stores the number of stims presented (6, 12, 24, 48)
arrayCondition	Practice: 1 => 4 stims; 2 => 12 stims test: 1 => 6 stims; 2 => 12 stims; 3 => 24 stims; 4 => 48 stims
targetPresent	1 = target presented in array; 0 = otherwise
targetColor	The color of the presented target ("red" vs. "green")
targetLetter	The target letter: "L" vs. "T"
targetRotation	The degree of the target rotation
currentTarget	Stores the itemnumber of the current target item cue
picture.target.x	The horizontal screen position (in % of canvas width)
picture.target.y	The vertical screen position (in % of canvas height)
targetDistance	Calculates the distance (in %) from the target stim to the center (fixation cross) relative to the screen canvas (portion of monitor used for stimulus display) (only valid for 'Target Present' trials) -> the value can be converted to absolute measurements by using 'canvasheightMM/canvaswidthMM'
canvasRatio	Calculates the ratio of canvas (=the part of the screen that is used by the script) height to height of monitor(in %)
response	The participant's response (scancode of response button: 18(E); 23(I))
response	Translates scancode of response button into response: 'yes' vs. 'no
responseCategory	Accuracy of response: 1 = correct response; 0 = otherwise
latency	The response latency (in ms); measured from: onset of stims (after presentation of cue)

Parameters

The procedure can be adjusted by setting the following parameters.

Name	Description	Default
Sizing Parameters
picSize	Proportional sizing of images in percentage of canvas height	10%
fixationSize	Proportional sizing of fixation cross in percentage of canvas height	10%
Timing Parameters
cueDuration	Duration (in ms) of cue	1000
responseWindow	Duration (in ms) of response window	7000
spacebarReminder	The delay (in ms) after which a spacebar-response reminder is presented	2000
feedbackDuration	Duration (in ms) of feedback duration	2000
readyDuration	Duration (in ms) of get-ready trial	3000
Response Keys
yesKey	The yes-key scancode; the left response key on QWERTY keyboard	"E"
noKey	The no-key scancode; the right response key on QWERTY keyboard	"I"

Visual Search Task - Divided Attention

Technical Manual

Background

References

Duration

Description

Procedure

Practice: Default

Test: Default

Trial Sequence:

Stimuli

Instructions

Summary Data

Data Fields

Raw Data

Data Fields

Parameters

Sizing Parameters

Timing Parameters

Response Keys