Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 28, 2012
Last Modified: January 02, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a threat dotprobe procedure to measure attentional bias towards threatening material. The implemented procedure is based on MacLeod et al (2007).
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: https://www.psy.uwa.edu.au/labs/cogemo/AttProbe1.html)
6 minutes
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: E or I) appears in the location of one of the words. Participants are asked to press one key if the probe is E and another if the probe is I.
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)
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 are not original to the task. They are provided by Millisecond.
They can be edited under section Editable Instructions.
File Name: dotprobe_macleod_summary*.iqdat
| Name | Description |
|---|---|
| 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 |
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
| 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) |
| tpISI | The interstimulus interval between offset of target and onset of probe in ms (default: 0) |
| probePosttrialPause | 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: >,<) |
| randomProbeX | 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) |
| propCorrect | Overall proportion correct of all test trials |
| meanRT | Overall mean latency in ms of correct responses of all test trials |
| propCorrectCongruent | Proportion correct of all congruent test trials (congruent = target/threat and probe position congruent) |
| propCorrectIncongruent | Proportion correct of all incongruent test trials (congruent = target/threat and probe position incongruent) |
| meanRTCongruent | Mean latency in ms of correct congruent test trials |
| meanRTIncongruent | 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) 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) |
File Name: dotprobe_macleod_raw*.iqdat
| Name | Description |
|---|---|
| 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 |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockcode | The name the current block (built-in Inquisit variable) |
| blocknum | The number of the current block (built-in Inquisit variable) |
| trialcode | The name of the currently recorded trial (built-in Inquisit variable) |
| trialnum | The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file. |
| 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) |
| randomProbeX | 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) |
| 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 (0 vs 1) |
| threatY-probeX | The y-coordinate (in %) of the threat/neutral/probe (and x-coordinate of probe) |
| itemNumber | The item number 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 |
| responseText | The label of the pressed response key |
| correct | Accuracy of response (1 = correct; 0 = error) |
| latency | The response latency in ms (measured from onset of probe until response) |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Design |
||
| 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) | 3 |
| randomProbeX | 1 = the x-coordinate of the probe is randomly determined within the space that the target previously occupied (see MacLeod et al, 2007) 2 = the probe is always presented at parameters.target_x (location of target) | 1 |
| probe1 | The symbol used for probe1 | "E" |
| probe2 | The symbol used for probe2 | "I" |
Sizing/Location Parameters |
||
| letterHeight | The height of the letter in % of screen height !!! 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. | 5% |
| targetTopY | The y-coordinate in % of the top target | 43% |
| targetBottomY | The y-coordinate in % of thebottom target | 57% |
| targetX | The x-coordinate of the target | 50% |
Timing Parameters |
||
| fixationDuration | The duration (in ms) of the fixation crosses | 500 |
| targetDuration | The duration (in ms) of the targets | 500 |
| tpISI | The interstimulus interval between offset of target and onset of probe in ms | 0 |
| probePosttrialPause | The interstimulus interval between offset of probe and begin of next trial in ms | 1000 |
Response Keys |
||
| responseKeyProbe1 | The response keys associated with probe1 | "E" |
| responseKeyProbe2 | The response keys associated with probe2 | "I" |