Return to the Auditory Stroop Task (Acoustic Dimensions) page


Script Author: Katja Borchert, Ph.D. ( for Millisecond Software, LLC
Date: 10-23-2014
last updated:  09-06-2021 by K. Borchert ( for Millisecond Software, LLC

Script Copyright © 09-06-2021 Millisecond Software

This script runs an auditory Stroop procedure.

The classic Stroop paradigm, using visual stimuli, demonstrates the interference of word meaning on naming 
the color in which the words are  written as measured by reaction time/accuracy  differences to 
color-meaning congruent  and color-meaning incongruent combinations. 
This Auditory Stroop Procedure tests the interference effect using auditory congruent and incongruent
stimuli combinations in three sound dimensions: pitch, loudness, duration.

Morgan, A.A.R. & Brandt, J.F. (1989). An Auditory Stroop Effect for Pitch, Loudness, and Time.

Participants hear Stroop and Non-Stroop words of 3 different acoustic dimensions (pitch, loudness, duration).

Stroop Words: words that are related to the acoustic dimension (e.g. pitch: low)
Non-Stroop Words: words that are neutral in relation to the acoustic dimensions (e.g. cat)

Depending on the acoustic dimension tested, they have to make categorical judgments and sort the word
into one of 2 categories as fast as possible.
Example: they hear 'cat' in a low-pitched voice and are asked to either press the response key dedicated to 
'low' or press the response key dedicated to 'high'.

the default set-up of the script takes appr. 30-40 minutes to complete

The default data stored in the data files are:

(1) Raw data file: 'auditorystroop_acousticdimensions_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
script.sessionid:					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. 

parameters.Earcondition:			1 = right ear is tested; 
									2 = left ear is tested
									3 = dual channels

values.dimension:					1 = pitch; 
									2 = loudness; 
									3 = duration; 
									4 = control_pitch; 
									5 = control_loudness; 
									6 = control_duration
values.level:						1 = high/loud/long; 
									2 = low/SOFT/short; 
									3 = neutral
values.congruence:					0 = neutral/control; 
									1 = congruent; 
									2 = incongruent
values.volume:						stores the current word volume
values.selecteditemnumber:			stores the actual itemnumber of the current stimulus (e.g. item 5 of level HIGH -> itemnumber: 11 of item.pitchwords)

values.practiceinstruct:			either Right (1) or Left (2) ear instructions for practice trials
for a practice trial

stimulusitem:						the presented stimuli in order of trial presentation

response:							the participant's response (scancode of response key)
										30 = A
										38 = L
values.responseCategory:			the interpreted key response: "high" vs. "low", "loud" vs. "SOFT", "long" vs. "short"

correct:							the correctness of the response (1 = correct; 0 = incorrect)
										Note: by design accuracy of response of "neutral stimuli" (level3 stimuli) is always 
										set to 1 in this script
latency: 							the response latency (in ms); measured from onset of word

block.practice.meanlatency:	stores the calculated mean response latency of the current practice block trial-by-trial
block.practice.sdlatency:			stores the calculated standard deviation of the response latencies of the current practice block trial-by-trial

(2) Summary data file: 'auditorystroop_acousticdimensions_summary*.iqdat' (a separate file for each participant)

computer.platform:					the platform the script was run on (win/mac/ios/android)
script.startdate:					date script was run
script.starttime:					time script was started
script.subjectid:					assigned subject id number
script.groupid:						assigned group id number
script.sessionid:					assigned session id number
script.elapsedtime:					time it took to run script (in ms); measured from onset to offset of script
script.completed:					0 = script was not completed (prematurely aborted); 
									1 = script was completed (all conditions run)

parameters.Earcondition:			1 = right ear is tested; 
									2 = left ear is tested
									3 = dual channels

expressions.propcorr_C_P:			proportion correct congruent pitch trials
expressions.propcorr_IC_P:			proportion correct incongruent pitch trials
expressions.meanRT_C_P:				mean RT (in ms) of correct congruent pitch trials
expressions.meanRT_IC_P:			mean RT (in ms) of correct incongruent pitch trials
expressions.meanRT_N_P:				mean RT (in ms) of neutral pitch trials
(same for loudness 'L' and duration 'D' )

expressions.propcorr_comp_ctrlP:	proportion correct comparison control pitch trials (comparison to congruent and incongruent trials)
expressions.meanrt_comp_ctrlP:		mean RT (in ms) of correct comparison control pitch trials
										!NOTE: comparison control trials = level 1 and level 2 (excluding the neutral stimuli)
expressions.meanrt_N_ctrlP:	mean RT (in ms) of neutral (level3) control pitch trials
(same for control loudness 'ctrlL' and control duration 'ctrlD' )


6 acoustic dimensions (pitch/pitchcontrol, loudness/loudnesscontrol, duration/durationcontrol): tested within-subject, mixed design
	!!!NOTE: if the acoustic dimensions (pitch/loudness/duration) should be tested in a blocked-design, go to 
	section EXPERIMENT and follow instructions
3 levels per acoustic dimension (e.g. pitch: low, high, neutral): tested within-subject, mixed design
6 stimuli per acoustic dimension
3 repetitions per stimuli
Stimulus Onset Asynchrony: 5s => soundfiles are presented 5s apart (Editable Parameters)

=> 6 acoustic dimensions x 3 levels x 6 stimuli x 3 repetitions = 2 x 324 trials

Note: Ear condition: parameters.Earcondition (Editable Parameters) sets whether the stimuli are presented through one ear (left or right)
as done by Morgan & Brandt (1989) or both ears at the same time. By default, this script runs the dual channels conditions.

Response key assignments to left or right: by default the left and right response keys are the 'A' and 'L' keys (change under Editable Parameters)
Assignment of low-high, soft-loud, short-long response keys to the left and right response key (2 possible orders) is counterbalanced 
by odd vs. even groupnumber (See section EXPERIMENT for more info)

(1) Stabilization: participants are asked to respond randomly with the left and right response keys to various beeps (20 trials, editable parameter)
(2) Familiarization: participants are presented all experimental stimuli but no response is required. The presentation
stream can be paused in this script and the last stimuli repeated.
!!!Note: parameters.run_stabilization/parameters.run_familiarization (Editable values) control if these blocks are run.
If parameters.session_nr > 1, these values are automatically set to false (and these training blocks are skipped)

(3) Practice: participants are asked to respond to a block of 12 randomly selected experimental stimuli by pushing the response button that 
corresponds to the instructions (e.g. LEFT/RIGHT) on the screen. LEFT/RIGHT instructions are randomly selected without replacement.
Participants have to hit a certain criterium to move from practice otherwise another block of 12 trials is started.

Criterium to quit practice: 
If the standard deviation of the response latencies of those 12 trials < 50% of the mean latency of those 12 trials (Morgan & Brandt, 1989, p.597)

Experimental Block:
(4) 324 trials: runs all 54 possible trials of each acoustic dimension (6 acoustic dimensions)
(54 => 3 levels x 6 stimuli per level x 3 repetitions per stimuli)

!Note: the semi-random order of the 324 trials is generated before each session by 
included helper script 'stimordergeneration.iqx' with the following constraints:
the same dimension (pitch, loudness, duration, control) cannot be run consecutively
(this includes not running a pitched control word after a pitched stroop word etc.)

The provided sound files are not original to Morgan & Brandt (1989). They are provided by Millisecond Software.
All recordings by a male native speaker of American English.
Pitch & Duration were manipulated in Audacity.
Volume is manipulated by script itself
(neutral volume is set to be at -1000 for all conditions; loud is set to be at 0; and soft is set to be at -2000 - editable values)

Stimuli can be exchanged under section Editable Stimuli

The provided instructions are not original to Morgan & Brandt (1989). They are provided by Millisecond Software.
The instructions are presented in the form of html pages. To change the instructions, edit the corresponding
html files. 
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).

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:

/responsekeyleft:						the left response key ("A")
/responsekeyright:						the right response key ("L")

/Earcondition:							1 = right ear is tested; 2 = left ear is tested; 3 = dual channels (default)

/familiarization_duration:				duration (in ms) of the stimuli presentations during familiarization trials (default: 2000ms)

/run_Stabilization:						true: runs the stabilization procedure 
										false: does not run the stabilization procedure => might have to update default instructions
/StabilizationTrials:					number of stabilization trials to run (default: 20)	=> Max number that can be run is 108									

/run_familiarization:					true: runs the familiarization procedure
										false: does not run the familiarization procedure => might have to update default instructions
										Note: if parameters.session_nr = 2; parameters.run_Stabilization and parameters.run_familiarization are set to fault automatically

/soa:									stimulus onset asynchrony: time between onset of one stimulus and the onset of the next
										in ms (default: 5000) -> every 5 s a new word is spoken.

Volume Adjustment:
/loudvolume:							volume setting for the loud volume (default: 0)
											Note: a setting of 0 plays the sound file at the recorded volume (0 is the max setting)
/neutralvolume:							volume setting for all neutral sound files (default: -1000)
											Note: a slight volume reduction
/softvolume:							volume setting for all soft sound files (default: -2000)