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IMAGE DOT PROBE TASK
Measure of Attentional Bias
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Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date: 05-28-2015
last updated: 02-22-2022 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC
Script Copyright © 02-22-2022 Millisecond Software
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BACKGROUND INFO
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This script implements a dotprobe procedure to measure attentional bias with images.
The implemented procedure is based on:
Miller, M.A. & Fillmore, M.T (2010). The effect of image complexity on attentional bias
towards Category1-related images in adult drinkers. Addiction, 105, 883–890.
Millisecond Software thanks Dr. Fillmore for ample assistance and generously sharing the original stimuli!
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TASK DESCRIPTION
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After presentation of a fixation cross in the center of the screen, participants are presented with
2 pictures from two categories (here: Alcohol and Neutral pictures). The position of the pictures is randomly
chosen to be either left or right to the location of the fixation cross. After a short duration,
the two pictures disappear and a probe stimulus (here: X) appears in the location of one of the
pictures. Participants are asked to press one key if the probe is left and another if the probe is right.
Attentional Bias Measures (AB) are provided for Category1 (here: Alcohol) and Category2 (here: Filler).
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DURATION
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the default set-up of the script takes appr. 4 minutes to complete
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DATA FILE INFORMATION
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The default data stored in the data files are:
(1) Raw data file: 'igenericdotprobe_images_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)
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.
task: 1 = practice; 2 = test
category: 1 = category1 ; 2 = category2
Congruence: 1 = probe and target (e.g. category1) position same; 2 = probe and target (e.g. category1) position different
target_position: 1 = target (e.g. category1) image on left; 2 = target (e.g. category1) image on right
comp_x-probe_x: the x-coordinate (in %) of the target (e.g. category1)/ comp ('paired with target') /probe stims
itemnumber: itemnumber of currently selected image
target_image: stores the currently presented target (e.g. category1) image
comp_image: stores the currently presented comp ('paired with target') image
response: the participant's response (scancode of response button)
49 = N (left key)
50 = M (right key)
latency: the response latency in ms (measured from onset of probe)
correct: accuracy of response (regardless of whether latency >= parameters.minimum_latency)
1 = correct; 0 = incorrect
valid: latency in ms that is >= parameters.minimum_latency
validCorrect: 1 = response was correct AND latency was >= parameters.minimum_latency; 0 = otherwise
(2) Summary data file: 'genericdotprobe_images_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)
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)
NOTE: all latency/accuracy summary variables are based on correct responses with latencies >= parameters.minimum_latency (default: 100ms)
propcorrect: proportion correct overall
meanrt: overall mean latency (in ms)
propcorrect_congruent_Category1: proportion correct in congruent Category1 trials
meanrt_congruent_Category1: mean latency of congruent Category1 trials
propcorrect_incongruent_Category1: proportion correct in incongruent Category1 trials
meanrt_incongruent_Category1: mean latency of incongruent Category1 trials
AB_Category1: Attentional Bias for Category1 pics : If AB_Category1 > 0
=> faster mean latencies to congruent Category1 trials than incongruent ones
propcorrect_congruent_Category2: proportion correct in congruent Category2 trials
meanrt_congruent_Category2: mean latency of congruent Category2 trials
propcorrect_incongruent_Category2: proportion correct in incongruent Category2 trials
meanrt_incongruent_Category2: mean latency of incongruent Category2 trials
AB_Category2: Attentional Bias for Category2 pics ('targets'): If AB_Category2 > 0
=> faster mean latencies to congruent Category2 trials than incongruent ones
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EXPERIMENTAL SET-UP
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2 categories tested (Category1: Category1; Category2: Category2); within-design
- 1 block of 10 practice trials
- 1 block of 80 trials: 40 Category1 trials (Category1-neutral pairings) and 40 Category2 (Category21-Category22 pairings)
10 Category1/neutral simple pictures, all pictures presented 4 times
=> right/left, followed by prime/not followed by prime => 10 * 4 = 40 trials
- Category2 Trials: same for Category2 trials
Note: all 80 trials are randomly sampled without replacement
DEFAULT TRIAL SEQUENCES
fixation cross (500ms) -> target image pair (1000ms) -> tp_isi (0ms)-> probe (max. 1000ms) (latency measured from onset of probe until response or offset of probe; whichever comes first)
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STIMULI
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Stimuli were generously shared by Dr. Fillmore and can be easily edited under EDITABLE STIMULI
The images for Category 1 depict Alcohol images (such as a beer can) and neutral Comps (such as soda cans)
The images for Category 2 depict Filler (neutral) images and neutral Comps
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INSTRUCTIONS
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Original Instructions were generously shared by Dr. Fillmore.
They have been slightly edited by Millisecond Software and provided
as htm/html pages that 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:
/ReadyDuration: the duration (in ms) of the get-ready-trial (default: 3000ms)
/fixationduration/targetduration: the duration of the fixation cross (default: 500ms)/the targets (default: 1000ms)
/tp_isi: target-probe interstimulus interval in ms (default: 0ms)
/probeduration: the duration of the probe presentation (default: 1000ms)
Note: by default this scripts allows for responses for the entire probe duration;
the trial terminates after parameters.probeduration is over
/iti: intertrialpause in ms (default: 0ms)
/probe: the symbol used for the probe (default: X)
/responsekey_left: the left response button (default: "N")
/responsekey_right: the right response button (default: "M")
/minimum_latency: the minimum latency of a correct response that is included into summary variables
(default: 100ms)
Physical Settings of Display: Note: change the settings to optimize the display on your computer screen
/target_left_x-target_right_x: the x-coordinate in % of the right/left target (default: 27%, 73%)
/target_y: the y-coordinate of the target (default: center at 50%)
/fixationcross_height: the height of the fixation cross in canvas height percentage (default: 5%)
/probe_height: the height of the probe in canvas height percentage (default: 5%)
/imageheight: the height of the image in canvas height percentage (default: 40%)
