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								DICHOTIC LISTENING TASK (Consonant-Vowel approach)

Script Author: Katja Borchert, Ph.D. ( for Millisecond Software, LLC
Date: 04-02-2012
last updated: 01-15-2016 by K.Borchert ( for Millisecond Software LLC

Copyright © 01-15-2016 Millisecond Software


This script implements the primed dichotic listening task using the Consonant-Vowel (CV) Nonsense Syllables 
approach described in:

Saetrevik, B. &  Hugdahl, K. (2007) . Endogeneous and exogeneous control of attention in dichotic listening. 
Neuropsychology, 21, 285-290.

After hearing two nonsense syllables simultaneously spoken in the left and right ear, participant are asked to select their target
(=depends on instructions) out of 6 possible choices. The target is determined by the instructions that participants receive that 
may specify which ear (left or right) to pay attention to. In this experiment, participants also listen to a prime syllable that is
played in both ears BEFORE the simultaneous probe syllables are played. The prime can match one of the two probe syllables or none.

The default data stored in the data files are:

(1) Raw data file: 'DichoticListening_syllables_raw*.iqdat' (a separate file for each participant)

build:							Inquisit build
computer.platform:				the platform the script was run on
date, time, subject, group:		date and time script was run with the current subject/groupnumber ( used to counterbalance color)
blockcode, blocknum:			the name and number of the current block
trialcode, trialnum: 			the name and number of the currently recorded trial
									(Note: not all trials that are run might record data) 
primecondition:					0 = noprime, 1 = left; 2 = right (codes the current prime condition)
left/right/prime:				the index of the left/right/prime syllable
response:						the participant's response (e.g. selected button)
correct:						the correctness of the response (1 = correct; 0 = error)
latency: 						the response latency (in ms)
values.response:				0 = error (response does not match left or right syllable)
								1 = response matches left syllable
								2 = response matches right syllable

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

script.startdate:						date script was run
script.starttime:						time script was started
script.subjectid:						subject id number
script.groupid:							assigned group id							group subject was assigned to
script.elapsedtime:						time it took to run script (in ms)
computer.platform:						the platform the script was run on
/completed:								0 = script was not completed; 1 = script was completed (all conditions run)
sumleftresponses/sumrightresponses:		total of all left matching/right matching responses


Trial Flow:
Prime (both ears) ---500ms pause--> Targets (left/right ear) ---500ms---> Response Screen: 6 possible syllables arranged in a clockwise fashion

Experimental Design:
(I) 3 within subject instruction blocks 
1) NF (not-forced): instructions don't specify which ear to pay attention to  ("Select the one you heard best")
2) LF (left-forced): instructions specify to pay attention only to the LEFT ear ("Select the left target")
3) RF (right-forced): instructions specify to pay attention only to the RIGHT ear ("Select the right target")

After a short practice session (NF), the script starts every participant in condition NF. The order LF-RF / RF-LF is then counterbalanced 
between participants by groupnumber. There are 80 trials in each instruction condition (=240 trials total) 
(see Saetrevik & Hugdahl, 2007).

(II) 3 within priming conditions
1) No prime: the prime is unrelated to the target syllables
2) Left prime: the prime is the left target syllables
3) Right prime: the prime is the right target syllables
the 3 priming conditions are randomly sampled (without replacement) during each instruction condition: 
50% of the trials in each instruction conditions are noprimes (40trials), 25% are left primes (20trials), and 25% are right primes (20trials) 
(see Saetrevik & Hugdahl, 2007)

(III) Dichotic Listening Task (trial.dichotic: presentation of target syllables, trial.dichoticresponse: selection of target syllable out of 6 possible targets):
*6 possible syllables: ba, ga, ta, ka, pa, da (spoken by a male native American English speaker)
*30 different pairings (no pairings of same syllables)
=> 8 x 30 = 240 trials, randomly distributed over the three instruction conditions
Note: if only the dichotic listening task is of interest check out 
trial.dichotic: presentation of target syllables 
trial.dichoticresponse: selection of target syllables out of 6 possible targets
as well as the necessary stimuli that go with it.

NOTE: Difference between script and Saetrevik & Hugdahl (2007):
a) The x/y screen positions of the 6 possible syllables targets in a clocklike arrangement is randomly determined for each participant in the script.
It is counterbalanced by Saetrevik & Hugdahl (2007).
b) the pause between targets and response screen was not explicitly specified in Saetrevik & Hugdahl (2007) (to the best of our knowledge).
It is set to 500ms (default) in this script and can be easily edited under Editable Parameters.

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:

prime_posttrialpause:					sets the pause after the prime is presented in ms (default: 500ms)
dichotic_posttrialpause:				sets the pause after the dichotic pairs are presented in ms (default: 500ms)
dichoticresponse_posttrialpause:		sets the pause after the response is made in in ms (default: 800ms) 

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