Return to the NBack Task (letter stimuli) page
						
						SINGLE N-BACK TASK NON-ADAPTIVE (1-KEY VERSION)- LETTERS
SCRIPT INFO

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software LLC
Date: March, 2012
last updated: 01-20-2016 by K.Borchert (katjab@millisecond.com) for Millisecond Software LLC

Copyright © 01-20-2016 Millisecond Software


BACKGROUND INFO

											*Purpose*
The current script is based on the SingleTaskNBack.exp script which implements the single-task version of the N-Back procedure as 
described in the following publication:

Jaeggi, Susanne M.; Studer-Luethi, Barbara; Buschkuehl, Martin; Su, Yi-Fen; Jonides, John; Perrig, Walter J. (2010). The 
relationship between n-back performance and matrix reasoning - implications for training and transfer. Intelligence, 38, 625-635.

The current script is adapted to implement the procedure of the Single N-back task using letters as described in:
Ragland, J.D., Turetsky, B.I., Gur, R.C, Gunning-Dixon, F., Turner, T, Schroeder, L., Chan, R., & Gur, R.E. (2002).Working Memory
for Complex Figures: An fMRI Comparison of Letter and Fractal n-Back Tasks. Neuropsychology, 16, 370-379.

This Inquisit script provides trials and instructions for single n-back tasks with 20 upper case consonants for 4 levels of N
(N = 0, N = 1, N = 2, N = 3). Other levels of N can be implemented with minimal change.

											  *Task*
In the 1-key single n-back task, participants are shown a sequence of stimuli (here: a sequence of white letters
on a black background) and are asked to indicate whether the currently presented stimulus fulfills the following criteria:

for N=0 trials*:
- is the letter the same as the first letter presented in the sequence? If so (it's a target), and press "A". If not, don't respond.

for N=1 trials:
- is the letter the same as the one that preceded it? If so (it's a target), and press "A". If not, don't respond.

for N=2 trials:
- is the letter the same as the one presented two trials before? If so (it's a target), and press "A". If not, don't respond.

for N=3 trials:
- is the letter the same as the one presented three trials before? If so (it's a target), and press "A". If not, don't respond.

*Note: The implementation for 0-nback tasks in this script differs from the procedure used by Jaeggi and collegues in her research.
Jaeggi and collegues used a pre-defined shape. In this script, the target shape is defined at runtime for each participant during the first trial. 
Participants are instructed to pay close attention to this first presentation and are warned that presentation time is short.
Furthermore in this script, the experimenter can set how long the target letter should be presented to participants in 0 nback trials, as well
as how much time before starting the actual task (after the target has disappeared)


DATA FILE INFORMATION: 
The default data stored in the data files are:

(1) Raw data file: 'SingleTaskNBack_letters_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 
blockcode:						the name of the current block
values.TotalBlocks:				the total number of experimental blocks run
trialcode:						the name of the current trial
starttrialcounter:				keeps track of how many start trials have been run
stimulusitem:					the letter presented
stimulusnumber: 				the item number of the presented letter
values.currenttarget:			the item number of the current target
response:						the response of the participant
correct:						the correctness of the response
latency:						how fast a participant responded within the given timeframe, if at all (in ms)
values.trial_Hit:				whether the response was a Hit (=1)
values.trial_FA:				whether the response was a False Alarm (=1)
values.trial_Miss:				whether the response was  Miss (=1)
values.trial_CR:				whether the response was a Correct Rejection ( = 1)
values.Hits:					the sum of Hits in a block
values.FalseA:					the sum of False Alarms in a block
values. Misses:					the sum of Misses in a block
values.CorrReject:				the sum of Correct Rejections in a block
values.TotalHits:				the sum of total hits across all experimental blocks
values.TotalFA:					the number of total false alarms across all experimental blocks
values.DV:						the proportion of (TotalHits - TotalFA)/number of experimental blocks

(2) Summary data file: 'SingleTaskNBack_letters_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:					group id number
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 (prematurely aborted); 1 = script was completed (all conditions run)
values.TotalHits:				the sum of total hits across all experimental blocks
values.TotalFA:					the number of total false alarms across all experimental blocks
values.DV:						the proportion of (TotalHits - TotalFA)/number of experimental blocks


EXPERIMENTAL SET-UP:
- After instructions, participants receive 9 trials of practice per level N tested (here: N = 0 to N = 3) , 
(-> can be changed to eliminate N = 3 as was done by Ragland et al (2002))
- once practice is done, participants get the option to repeat practice
- After practice, participants receive 3 blocks per level of N tested. Which particular level a participant works on is
pseudo-randomly determined (see Ragland et al, 2002).
- the instructions are self-paced as a default, to change them to a timed format (default = 9s, see Ragland et al, 2002),
	follow instructions under parameters.instruction_duration

Block Information:
- Each single n-task block consists of 15+ trials (Ragland et al, 2002) using 20 different consonants. 
=> + trials are the N trials that cannot display target shapes yet (=start trials). Their numbers vary depending on N. 
		The data collected during these  start trials are NOT included in performance counts for Correct Rejections/False Alarms.
=> Of the actual  15 experimental trials, 5 present a target and 10 do not (1:2 ratio as in Ragland et al, 2002). 
- The computer selects randomly 
a) whether it is a target trial or not and 
b) what letter to show if it is not a target trial

Trial Information:
- Each trial presents the letter for 500ms and waits another 2000ms before presenting the next letter in the sequence
(see Ragland et al. for InterstimulusInterval = 2500ms). The trialduration can be edited by experimenter.
- Participants have the entire 2500ms to respond by pressing "A" if they detect a target.


INFORMATION FOR CODE-CHANGES (e.g. ADDITIONAL/DIFFERENT LEVELS OF N)

Instructions for changing code for additional Ns are provided with this script. Please check the following sections for the relevant info:
1. Custom Values
2. Instructions: (a) Instruction Slides -> Editable Instructions (b) Instruction Blocks -> section Instructions (block.Nbackinstruct_start)
3. Trials
4. Blocks: (a) Practice (b) Experimental


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:

trialduration:							Interstimulusinterval (in ms) for regular n-back trials, default = 2500ms, 
posttrialpause_aftertarget0:			the posttrialpause (in ms) after the target in 0nback tasks disappears from sight and the actual 0 nback testing starts
												(default = 2000ms, to make it comparable to the remaining trials)
showtarget0:							the amount of time the target for N = 0 trials should be presented; default = 3000
instruction_duration:					the time the instructions for each experimental block are shown (in ms), default = 9000ms
										only applies if instructions for experimental blocks are NOT self-paced
												(see INSTRUCTIONS -> INSTRUCTION TRIALS -> trial.expinstructiontrial for further info)
										NOTE: the default for this script are self-paced instructions
debugmode = 0							debugmode = 1: targetalerts are shown on screen, 
										debugmode = 0, no targetalerts are shown (default)
/stimulusPresentationtime:		the presentation time (in ms) of the stimuli (default: 500ms)

(in general: if levels of N are changed, adjustments need to be made to instructions and list.Nlevel)

Copyright © Millisecond Software. All rights reserved.
Contact | Terms of Service | Security Statement | Employment