Montreal Imaging Stress Task

Technical Manual

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

Created: June 16, 2015

Last Modified: April 01, 2026 by K. Borchert (katjab@millisecond.com), Millisecond

Background

This script implements an Inquisit version of the Montreal Imaging Stress Test as (MIST) described in Dedovic et al (2005). The MIST was designed to induce moderate psychosocial stress in a functional imaging environment (fMRI or PET scans). It combines difficult mental arithmetic under time pressure with negative performance evaluations.

Because the MIST was developed as a stress test to be used under imaging conditions (e.g. fMRI, PET), where participants might have limited access to keyboards/touchscreens, the responses are collected by mouse input. This script is a best guess effort of Millisecond based on published information.

References

Dedovic, K.; Renwick, R,; Khalili Mahani, N.; Engert, V.; Lupien, S.J. & Pruessner, J.C. (2005). The Montreal Imaging Stress Task: using functional imaging to investigate the effects of perceiving and processing psychosocial stress in the human brain. J Psychiatry Neurosci, 30, 319-325.

Duration

40 minutes

Description

Participants are asked to solve arithmetic problems of 5 different difficulty levels under 3 different stress conditions. In the high stress condition (experimental condition), the participant's performance is manipulated to be relatively low by a) timing performance (e.g. if too many are correct, less time is allocated) b) comparing the participant's performance to the "average" performance (80-90% correct) by means of a "performance bar" In the control condition, the participants are asked to solve the same problems but without overt timing and without presenting the performance bar. In the rest condition, participants are simply asked to rest. In all conditions the participants are asked to control the selection of the solution by "dialing" via mouse selections: left button (dials counterclockwise), right button (dials clockwise), middle button (submits the response).

Procedure

Design: 3 Conditions (Experimental, Control, Rest) X 5 Difficulty Level, Tested Within

(A) 5 levels of difficulty: tested in blocked format

In this script version, the levels are defined as follows:
1: 2 1-digit integers (0-9), only + or -, solution 0-9 (1 digit)
2: 3 1 digit integers (0-9), only +,- (no repeated operations, order of operations random)
3: 3 integers, 1-2 integers are double digits (0-99), +,-,* (no repeated operations, selection and order of operations random), solution 0-9 (1 digit)
4: 4 integers, 1-2 integers are double digits (0-99), +,-,* (no repeated operations, selection and order of operations random), solution 0-9 (1 digit)
5: 4 integers, 1-4 integers are double digits (0-99), *, / are a must, then either + or - (order of operations random), solution 0-9 (1 digit)

the problems are pregenerated for this script (see also Dedovic et al, p.320)

(B) 4 different conditions:
1) Training:
- administered outside of imaging equipment
- uses the mouse to control the selection of the solution (the 'dials') -> Dedovic et al (2005) use keyboard input for training
- minimum suggested duration: 2 minutes for entire training block (this translates to Min = 24s for each level of difficulty);
he default in this script is set to 5 minutes (=1 minute/level of difficulty)
- presents a random order of the 5 difficulty level blocks
- calculates average time participants used to respond to each problem (regardless of accuracy) for each level of difficulty.
The uncorrected latencies are used in this script to ensure that initial timelimits can be calculated.
- does not put a time limit on performance
- does not give overall performance feedback in the form of a performance bar
- presents feedback (correct, incorrect) for individual problem for 500ms (editable parameter)
training ends with a slide that says "Please Wait" (to continue the experimenter has to press the Spacebar - participant cannot move from here with the mouse)

2) Experimental:
- minimum suggested duration: 2 minutes per level of difficulty
this timelimit is based on our interpretation of (->"individual runs" p.321, right column)
- presents a random order of the 5 difficulty level blocks
- puts a time limit on performance
a) at the start of a block uses training mean latency for the currently tested level of difficulty but shortens it by 10% (= 90% of the training mean response times)
b) continuously tracks the performance and response time of the last 3 trials
=> if the last 3 trials are all correct: adjust time limit by using the average response duration of the last 3 trials but shorten it by 10%
=> if the last 3 trials are all errors (or timeouts): adjust time limit by lengthening the current timeout by 10%
c) presents a timer on screen that counts down the seconds (Dedovic et al, 2005 used a progress bar)

- presents a performance bar that presents the "average" performance as being in the green (good) region of performance and the participant's
performance as being (likely) in the red (bad) region of performance (average displayed performance is calcuated across experimental difficulty levels)

- presents feedback (correct, incorrect, timeout) for individual problems for 500ms (editable parameter)

- adds an intertrial interval (ITI): the duration of the intertrial interval is based on parameters.iti_test (editable parameter) which gets
adjusted by the difference of the average response latency for the tested level (based on training performance) minus the current response latency.
If the current response latency was faster, the ITI increases. If the current response latency was slower (unlikely as a timeout is imposed) the ITI decreases
the ITI was added so that control and experimental trials could (roughly) be matched in frequency.
(Dedovic et al, 2005, p.321: "To match the frequency of mental arithmetic tasks [in experimental and control condition], the time between tasks is varied as a function of the time limit
imposed during the experimental condition, so that the total number of tasks presented per condition is identical.")
The idea is that if the response time is equal to the training response time (which is run under similar conditions to the control condition)
the ITI is parameters.iti_test. If it's shorter (because of the timeout) then the ITI gets adjusted up - otherwise down.
This works theoretically AS LONG AS there is still a positive ITI (>=0ms) left at the end. If a control trial (or experimental trial, though that is less likely)
is longer than the average response time by parameters.ITI then the number of trials in the experimental and control condition might differ.

-each experimental blocks ends with a slide that informs participants of their average performance; followed by a slide that says "Please Wait"
(to move on the experimenter has to press the Spacebar - participants cannot move on from here with the mouse)

3) Control:

- minimum suggested duration: 2 minutes per level of difficulty
- presents a random order of the 5 difficulty level blocks
- does not put a time limit on performance
- does not present a performance bar
- presents feedback (correct, incorrect, timeout) for individual problems for 500ms (editable parameter)
- adds an intertrial interval (ITI): the duration of the intertrial interval is based on parameters.iti_test (editable parameter) which gets
adjusted by the difference of the average response latency for the tested level (based on training performance) minus the current response latency.
If the current response latency was faster, the ITI increases. If the current response latency was slower (unlikely as a timeout is imposed) the ITI decreases
the ITI was added so that control and experimental trials could (roughly) be matched in frequency.
(Dedovic et al, 2005, p.321: "To match the frequency of mental arithmetic tasks [in experimental and control condition], the time between tasks is varied as a function of the time limit
imposed during the experimental condition, so that the total number of tasks presented per condition is identical.")
- each control blocks ends with a slide that says "Please Wait"

4) Rest: inside imaging equipment
- presents the userinterface with a message to take a break and not move the mouse until told to do so
the rest block ends with a slide that says "Please Wait" (to move on the experimenter has to press the Spacebar - participant cannot move from here with the mouse)

The order of the 3 test conditions (experimental, control, rest) is counterbalanced by groupnumber (6 different groupnumbers run the 6 possible orders)
To change the experimental procedure (e.g. if no rest condition should be run), go to section EXPERIMENT and delete the blocks
that should not run.

groupnumber1: exp, ctrl, rest
groupnumber2: exp, rest, ctrl
groupnumber3: ctrl, exp, rest
groupnumber4: ctrl, rest, exp
groupnumber5: rest, exp, ctrl
groupnumber6: rest, ctrl, exp

Stimuli

this script uses pregenerated sequences for the 5 levels of difficulty. The problems used can be edited under
section "Editable Lists"

Instructions

this script uses instructions that are not original to Dedovic et al (2005).
They can be edited in script montrealstresstest_instructions_inc.iqjs (language-dependent)

Summary Data

File Name: montrealstresstest_summary*.iqdat

Data Fields

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
meanRTComplete1	Stores the mean response time in ms of level 1 training trials (not corrected for accuracy)
meanRTComplete2	Stores the mean response time in ms of level 2 training trials (not corrected for accuracy)
meanRTComplete3	Stores the mean response time in ms of level 3 training trials (not corrected for accuracy)
meanRTComplete4	Stores the mean response time in ms of level 4 training trials (not corrected for accuracy)
meanRTComplete5	Stores the mean response time in ms of level 5 training trials (not corrected for accuracy)
numberCorrectExp	Number of correctly solved experimental trials
percentCorrectExp	Percent correct of experimental trials across levels
percentCorrectExp1	Percent correct of level 1 experimental trials
percentCorrectExp2	Percent correct of level 2 experimental trials
percentCorrectExp3	Percent correct of level 3 experimental trials
percentCorrectExp4	Percent correct of level 4 experimental trials
percentCorrectExp5	Percent correct of level 5 experimental trials
meanrtExp	Mean correct response latency in ms of experimental trials across levels
meanrtExp1	Mean correct response latency in ms of level 1 experimental trials
meanrtExp2	Mean correct response latency in ms of level 2 experimental trials
meanrtExp3	Mean correct response latency in ms of level 3 experimental trials
meanrtExp4	Mean correct response latency in ms of level 4 experimental trials
meanrtExp5	Mean correct response latency in ms of level 5 experimental trials
numberCorrectExp	Number of correctly solved control trials
percentCorrectCtrl	Percent correct of control trials across levels
percentCorrectCtrl1	Percent correct of level 1 control trials
percentCorrectCtrl2	Percent correct of level 2 control trials
percentCorrectCtrl3	Percent correct of level 3 control trials
percentCorrectCtrl4	Percent correct of level 4 control trials
percentCorrectCtrl5	Percent correct of level 5 control trials
meanrtCtrl	Mean correct response latency in ms of control trials across levels
meanrtCtrl1	Mean correct response latency in ms of level 1 control trials
meanrtCtrl2	Mean correct response latency in ms of level 2 control trials
meanrtCtrl3	Mean correct response latency in ms of level 3 control trials
meanrtCtrl4	Mean correct response latency in ms of level 4 control trials
meanrtCtrl5	Mean correct response latency in ms of level 5 control trials
countExp1	Stores the number of level 1 concluded experimental trials
countExp2	Stores the number of level 2 concluded experimental trials
countExp3	Stores the number of level 3 concluded experimental trials
countExp4	Stores the number of level 4 concluded experimental trials
countExp5	Stores the number of level 5 concluded experimental trials
countCtrl1	Stores the number of level 1 concluded control trials
countCtrl2	Stores the number of level 2 concluded control trials
countCtrl3	Stores the number of level 3 concluded control trials
countCtrl4	Stores the number of level 4 concluded control trials
countCtrl5	Stores the number of level 5 concluded control trials

Raw Data

File Name: montrealstresstest_raw*.iqdat

Data Fields

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.
order	Order of Rest, Experimental and Control Condition
condition	1 = training 2 = experimental 3 = control 4 = rest
level	Stores the level of the presently presented problem
problem	Stores the presently presented problem
solution	Stores the solution to the presently presented problem
dialPosition	The currently 'highlighted' dial
response	The participant's response
acc	0 = Timeout 1 = correct response 2 = error response
error	1 = error: erroneous response or timeout 0 = correct response
latency	The response latency (in ms) of the current trial
rtComplete	Stores the response latency in ms of the current complete training/control/experimental problem
trialTimeout	Stores the max. duration in ms of the currently complete training/control/experimental task
currentTimeoutExp	Stores the max. duration in ms of the presented segment of the current experimental task ( each dial press starts a new trial segment, so trialtimeout needs to be continuously adjusted)
increaseTimeout	1 = the last 3 experimental responses were incorrect or timeouts 0 = otherwise
decreaseTimeout	1 = the last 3 experimental responses were all correct 0 = otherwise
meanLast3Errors	For exp condition only: calculates the the mean error performance during the last 3 trials (is set to -1 if there are fewer than 3 trials to report on)
currentMeanRT	The RT (in ms) of the last three responses

Parameters

The procedure can be adjusted by setting the following parameters.

Name	Description	Default
Timing Parameters
trainingTimeout	Sets the timeout for the training block (per difficulty level) in ms	60000
experimentalBlockTimeout	Sets the timeout of the individual experimental block (per difficulty level) in ms	120000
feedbackDuration	Sets the feedback duration in ms	500
restDuration	Sets the duration of the rest period in ms	60000
itiTest	The default length of the intertrial interval in ms in experimental and control task that would run if the response latency of the currently solved problem was equal to the one determined during training	1000
Ui Paramaters
whitePerformance	Sets the performance proportion of the performance bar that appears white performance > 80% appears green	80%
redPerformance	Sets the performance proportion of the performance bar that appears red	60%
averagePerformance	Sets the average performance that participant compares to -> used for the average performance triangle	85%
inactiveDialButtonColor	The color of the digit buttons (during experiment) when not active	"blue"
activeDialButtonColor	The color of the digit buttons (during experiment) when active the dial colors on the instruction pages need to be updated manually	"orange"

Montreal Imaging Stress Task

Technical Manual

Background

References

Duration

Description

Procedure

Design: 3 Conditions (Experimental, Control, Rest) X 5 Difficulty Level, Tested Within

Stimuli

Instructions

Summary Data

Data Fields

Raw Data

Data Fields

Parameters

Timing Parameters

Ui Paramaters