___________________________________________________________________________________________________________________ DOT PROBE TASK Measure of Attentional Bias ___________________________________________________________________________________________________________________ Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software LLC Date: 11-28-2012 last updated: 03-25-2024 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC Script Copyright © 03-25-2024 Millisecond Software ___________________________________________________________________________________________________________________ BACKGROUND INFO ___________________________________________________________________________________________________________________ This script implements a dotprobe procedure to measure attentional bias. The implemented procedure is based on: MacLeod, C. , Soong, L.Y., Rutherford, E., & Campbell, L.W. (2007). Internet-delivered assessment and manipulation of anxiety-linked attentional bias: Validation of a free-access attentional probe software package. Behavior Research Methods, 39, 533-538. (the free-access attentional probe software package as well as the stimuli used is available under: http://www.psy.uwa.edu.au/labs/cogemo/AttProbe1.html) ___________________________________________________________________________________________________________________ TASK DESCRIPTION ___________________________________________________________________________________________________________________ After presentation of a fixation cross in the center of the screen, participants are presented with 2 words from two categories (here: threat and neutral words). The position of the words is randomly chosen to be either above or below the location of the fixation cross. After a short duration, the two words disappear and a probe stimulus (here: < or >) appears in the location of one of the words. Participants are asked to press one key if the probe is < and another if the probe is >. ___________________________________________________________________________________________________________________ DURATION ___________________________________________________________________________________________________________________ the default set-up of the script takes appr. 6 minutes to complete ___________________________________________________________________________________________________________________ DATA FILE INFORMATION ___________________________________________________________________________________________________________________ The default data stored in the data files are: (1) Raw data file: 'dotprobe_macleod_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. ///parameter settings: probetaskselection: determines which type of dotprobe task to run 1 = probe always in threat position 2 = probe always in neutral position 3 = probe randomly in threat or neutral position (half the time in threat position) (default) randomprobe_x: 1 = the x-coordinate of the probe is randomly determined within the space that the target previously occupied (see MacLeod et al, 2007); default 2 = the probe is always presented at parameters.target_x (location of target) ///data: congruence: 1 = probe and target (threat) congruent; 2 = probe and target (threat) incongruent targetlocation: 1 = target is displayed top (and comp is presented bottom); 2 = target is presented bottom (comp is presented top) probeposition: 1 = probe is displayed on top; 2 = probe is displayed on bottom probetype: determines the type of the probe presented (1 vs. 2) threat_y-probe_x: the y-coordinate (in %) of the threat/neutral/probe (and x-coordinate of probe) itemnumber the itemnumber of the current word pair threatword-neutralword: contain the current stimuli text.probe.currentItem: current probe item response: the participant's response (scancode of response button): 18 vs. 23 correct: accuracy of response (1 = correct; 0 = error) latency: the response latency in ms (measured from onset of probe until response) (2) Summary data file: 'dotprobe_macleod_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) ///Task Parameters: probetaskselection: determines which type of dotprobe task to run 1 = probe always in threat position 2 = probe always in neutral position 3 = probe randomly in threat or neutral position (half the time in threat position) (default) fixationduration/targetduration: the duration of the fixation crosses in ms (default: 500ms)/the targets (default: 500ms) TP_ISI: the interstimulus interval between offset of target and onset of probe in ms (default: 0) probe_posttrialpause: the interstimulus interval between offset of probe and begin of next trial in ms (default: 0) probe1-probe2: the symbols used for probe1 and probe 2 (default: >,<) randomprobe_x: 1 = the x-coordinate of the probe is randomly determined within the space that the target previously occupied (see MacLeod et al, 2007); default 2 = the probe is always presented at parameters.target_x (right above fixation) ///Summary Variables: propcorrect: overall proportion correct of all test trials meanRT: overall mean latency in ms of correct responses of all test trials propcorrect_congruent: proportion correct of all congruent test trials (congruent = target/threat and probe position congruent) propcorrect_incongruent: proportion correct of all incongruent test trials (congruent = target/threat and probe position incongruent) meanRT_congruent: mean latency in ms of correct congruent test trials meanRT_incongruent: mean latency in ms of correct incongruent test trials TBI: threat bias index calculated by subtracting the mean latency of responses to probes in threat positions (congruent) from mean latency of responses to probes in neutral positions (incongruent) Note: MacLeod et al (2007) use the medians instead of the means =>If positive: attentional bias towards threats words (the bigger the number, the higher the attentional focus on the threat words) ___________________________________________________________________________________________________________________ EXPERIMENTAL SET-UP ___________________________________________________________________________________________________________________ 2 target positions (up, down) x 2 target-probe congruence (congruent, incongruent) x 2 probe symbols, tested within participants - 1 Block of 20 practice trials with digits; not original; practice trials give errorfeedback - 1 Block of 96 trials - it can be set (see section Editable Values) whether a) all the trials are threat-probe congruent b) all the trials are threat-probe incongruent c) 1/2 trials are congruent; 1/2 trials are incongruent (default) - Default trialsequence: fixation (500ms)->targets(500ms)->TP_ISI(0ms)->Probe (until response) -> ISI (1000ms) - stimuli pairs are randomly determined for each trial - target positions/target-probe congruence/probe symbol randomly determined - Probe can be right above the fixation cross or it is randomly placed in one of the previously occupied letter positions (default) (can be set under section Editable Values) ___________________________________________________________________________________________________________________ STIMULI ___________________________________________________________________________________________________________________ This script uses the stimuli generously provided by MacLeod et al (2007) on their website (see above) They can be edited under section Editable Stimuli Probes can be edited under section Editable Parameters. ___________________________________________________________________________________________________________________ INSTRUCTIONS ___________________________________________________________________________________________________________________ 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). ___________________________________________________________________________________________________________________ EDITABLE CODE ___________________________________________________________________________________________________________________ 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: /probetaskselection: 1 = probe always in threat position (all probe-threat congruent) 2 = probe always in neutral position (all probe-threat incongruent) 3 = probe randomly in threat or neutral position (half the time in threat position) (default) /fixationduration/targetduration: the duration of the fixation crosses (default: 500ms)/the targets (default: 500ms) /fixation_posttrialpause : the posttrialpauses for the fixation crosses/the targets/the probe /TP_ISI: the interstimulus interval between offset of target and onset of probe in ms (default: 0) /probe_posttrialpause: the interstimulus interval between offset of probe and begin of next trial in ms (default: 0) /probe1-probe2: the symbols used for probe1 (E) and probe 2 (I) /responsekey_probe1- responsekey_probe2: the response keys associated with probe1 (default: "E" - left response button) and probe2 (default: "I", right response button) /letterheight: the height of the letter in % of screen height (default: 5%) !!!NOTE: this script uses mono-spaced Courier New as the default font; we suggest to not change the fontstyle as the calculation of the width of a single letter is based on this particular fontstyle. /target_top_y-target_bottom_y: the y-coordinate in % of the top/bottom target (default: 25%, 75%) /target_x: the x-coordinate of the target (default: center at 50%) /randomprobe_x: 1 = the x-coordinate of the probe is randomly determined within the space that the target previously occupied (see MacLeod et al, 2007); default 2 = the probe is always presented at parameters.target_x (location of target)