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VISUAL SEARCH
(behavioral data only)
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Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date: 06-19-2017
last updated: 10-31-2023 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC
Script Copyright © 10-31-2023 Millisecond Software
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BACKGROUND INFO
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This script implements a basic visual search paradigm based on:
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.
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TASK DESCRIPTION
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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.
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DURATION
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the default set-up of the script takes appr. 25 minutes to complete
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DATA OUTPUT DICTIONARY
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The fields in the data files are:
(1) Raw data file: 'visualsearch_letters_raw*.iqdat' (a separate file for each participant)*
build: The specific Inquisit version used (the 'build') that was run
computer.platform: the platform the script was run on (win/mac/ios/android)
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
date, time: date and time script was run
subject, group: with the current subject/groupnumber
session: with the current session id
blockCode, blockNum: the name and number of the current block (built-in Inquisit variable)
trialCode, trialNum: the name and number of the currently recorded trial (built-in Inquisit variable)
Note: trialNum is a built-in Inquisit variable; it counts all trials run; even those
that do not store data to the data file such as feedback trials. Thus, trialNum
may not reflect the number of main trials run per block.
arraySize: stores the number of stims presented (6, 12, 24, 48)
targetPresent: 1 = target presented in array; 0 = otherwise
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 %)
currentTarget: stores the itemnumber of the current target item cue
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)
(2) Summary data file: 'visualsearch_letters_summary*.iqdat' (a separate file for each participant)*
inquisit.version: Inquisit version run
computer.platform: the platform the script was run on (win/mac/ios/android)
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
startDate: date script was run
startTime: time script was started
subjectId: assigned subject id number
groupId: assigned group id number
sessionId: assigned session id number
elapsedTime: time it took to run script (in ms); measured from onset to offset of script
completed: 0 = script was not completed (prematurely aborted);
1 = script was completed (all conditions run)
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
* separate data files: to change to one data file for all participants (on Inquisit Lab only), go to section
"DATA" and follow further instructions
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EXPERIMENTAL SET-UP
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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)
Note: 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)
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STIMULI
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provided by Millisecond Software - can be edited under section Editable Stimuli
Note:
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
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INSTRUCTIONS
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Instructions are not original to the task. They are provided by Millisecond Software
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).
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EDITABLE CODE
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check below for (relatively) easily editable parameters, stimuli, instructions etc.
Keep in mind that you can use this script as a template and therefore always "mess" with the entire code
to further customize your experiment.
The parameters you can change are:
/cueDuration: duration (in ms) of cue (default: 1000ms)
/responseWindow: duration (in ms) of response window (default: 7000ms)
/spacebarReminder: the delay (in ms) after which a spacebar-response reminder is presented (default: 2000ms)
/feedbackDuration: duration (in ms) of feedback duration (default: 2000ms)
/readyDuration: duration (in ms) of get-ready trial (default: 3000ms)
/picSize: proportional sizing of images in percentage of canvas height (default: 10%)
/fixationSize: proportional sizing of fixation cross in percentage of canvas height (default: 10%)
Response Keys:
/yesKey: the yes-key scancode (default: E); the left response key
/noKey: the no-key scancode (default: I); the right response key
