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										ERIKSEN FLANKER TEST
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Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date:  09-19-2012
last updated:  03-09-2020 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC

Script Copyright © 03-09-2020 Millisecond Software

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BACKGROUND INFO 	
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This script implements the original Flanker Test procedure by Eriksen & Eriksen (1974).
The Flanker test is an inhibition test to assess the ability to suppress inappropriate responses
evoked by task irrelevant information.											
											
Reference:

Eriksen, B.A. & Eriksen, C.W (1974) Effects of noise letters upon the identification of a target letter 
in a nonsearch task. Perception & Psychophysics, 16, 143-149.

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TASK DESCRIPTION	
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simple categorization task of 4 target letters (H, K, S, C) that appear above a fixation cross
into "angular"  vs. "curved" categories.
=> Press "Q" if it's H or K, press "P" if it's S or C.
Target letters can appear alone ("nonoise") or be flanked by noise letters ("noise") that can 
either be close together or far apart. 

Note: Responsekeys 
*can be changed under EDITABLE VALUES. 
*are counterbalanced by odd and even subjectnumbers

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DURATION 
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the default set-up of the script takes appr. XXX minutes to complete
(if no task duration is provided, please contact Millisecond Software
(katjab@millisecond.com)

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

(1) Raw data file: 'flankertest_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.
									
values.trialcount:					counts the number of trials
values.responsecondition:			counterbalanced response key condition
values.noisecondition:				stores the current noise condition (1-5)

									1)	noise equal to target: all 6 noise letters = target letter (e.g, HHHHHHH)
									2)	noise similar to target: all 6 noise letters = the other letter in the target category (e.g. KKKHKKK)
									3)	noise other target set: all 6 noise letters = one of the letters of the opposite target category (e.g. SSSHSSS)
									Note: choice of letter of opposite target category is balanced across experiment 
									4)	noise similar to target: noise = 3 letters that have similar characteristics (e.g. NWZHNWZ)
									Note: position of the three letters balanced across experiment
									5)	noise dissimilar to the target: noise = 3 letters with dissimilar characteristics (e.g. QJGHQJG)
									Note: position of the three letters balanced across experiment 

values.spacingcondition:			stores the current spacing condition (1-3)
values.trialtype:					contains all trialinformation
											(Example: "K53B" -> target K, condition 5, spacing 3, 
											B=refers to one of three possible rotations of the noise stimuli in condition 5)
stimulusitem.-
stimulusitem.4:						the presented stimuli
								
response:							the participant's response (scancode of response buttons)
									16 = Q (left)
									25 = P (right)

correct:							accuracy of response: 1 = correct response; 0 = otherwise
latency: 							the response latency (in ms); measured from onset of stimuli


(2) Summary data file: 'FlankerTest_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)

expressions.properror_noise1-
expressions.properror_noise5:		error proportion, separately for each noise condition

expressions.properror_spacing1-
expressions.properror_spacing3:		error proportion, separately for each spacing condition

expressions.properror_nonoiseM:		error proportion of nonoise trials tested in a mixed (M) design
expressions.properror_nonoiseB:		error proportion of nonoise trials tested in a blocked (B) design

expressions.meanRT_noise1-
expressions.meanRT_noise5:			mean latency of correct responses, separately for each noise condition		

expressions.meanRT_spacing1-
expressions.meanRT_spacing3:		mean latency of correct responses, separately for each spacing condition

expressions.meanRT_nonoiseM:		mean latency of correct responses to nonoise trials tested in mixed (M) design
expressions.meanRT_nonoiseB:		mean latency of correct responses to nonoise trials tested in blocked (B) design


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EXPERIMENTAL SET-UP 
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(A) DESIGN:
3 (spacings) x 5 (noise conditions) tested within participants,
2 control conditions of nonoise targets tested in a mixed vs. blocked format within participants

(B) SESSION SET-UP:
6 experimental sessions (see Eriksen & Eriksen, 1974, p.146)
1 experimental session: 3 blocks.Mixed (3*32 trials = 3*(28 noisetrials + 4 nonoisetrials)) + 1 block.blocked (12 nonoisetrials)

= 6*3*28 noisetrials + 6*3*4 nonoisetrials(mixed) * 6*1*12 nonoisetrials(blocked)
= 504 noisetrials + 72 nonoisetrials(mixed) + 72 nonoisetrials(blocked)

=> nonoisetrials:
nonoisetrials per target letter (4 letters) in mixed and blocked format= 72/4= 18 (see Eriksen & Eriksen, 1974, p.146)

=> noisetrials:
noisetrials per letter spacing condition (3 spacing conditions)= 504/33 = 168
noisetrials per letter spacing condition per noise conditions (5+2* conditions) = 168/7 = 24 (see Eriksen & Eriksen, 1974)
noisetrials per letter spacing condition per noise conditions per letter (4)= 24/4 = 6 

(C) INDEPENDENT VARIABLES:

1. SPACING CONDITIONS: Eriksen & Eriksen (1974)
1)about 0.06 degree visual angle separation (depends on viewing distance and font size) -
2)about 0.5 degree visual angle separation (depends on viewing distance and font size)
3)about 1 degree visual angle (depends on viewing distance and font size)
(4) distance from target to fixation cross: 0.5 degree visual angle)

!!!Note: SPACING = NEEDS FINE TUNING
the default coordinates for the noise stimuli in this script are only 
rough approximations. They need to be fine-tuned by each experimenter.
Specifically: fine tune 
*distance target-to-fixation cross under EDITABLE VALUES (parameters.fix_distance)
*spacings between stimuli under EDITABLE VALUES (parameters.spacing1, parameters.spacing2, parameters.spacing3)
*fontstyle: Erikson & Erikson (1974) used Paratipe 18point Futura Bold Style,
=> this script uses Monospaced Lucida Console, 0.5cm: can be changed under EDITABLE VALUES (parameters.fontheight_innm)
Note: If Monospaced Lucida Console is not available try a different monospaced fontstyle

2. NOISE CONDITIONS:
1)	noise equal to target: all 6 noise letters = target letter (e.g, HHHHHHH)
2)	noise similar to target: all 6 noise letters = the other letter in the target category (e.g. KKKHKKK)
3)	noise other target set: all 6 noise letters = one of the letters of the opposite target category (e.g. SSSHSSS)
Note: choice of letter of opposite target category is balanced across experiment 
4)	noise similar to target: noise = 3 letters that have similar characteristics (e.g. NWZHNWZ)
Note: position of the three letters balanced across experiment
5)	noise dissimilar to the target: noise = 3 letters with dissimilar characteristics (e.g. QJGHQJG)
Note: position of the three letters balanced across experiment 

*Note:
Eriksen & Eriksen (1974) ran double the amount of trials in noise conditions 4 and 5 than in the remaining 3 conditions
(refer to Eriksen & Eriksen, 1974, Table 3, p.147), numberwise this is equivalent to running 7 conditions

(D) BLOCKS:
Each block.mixed runs 32 trials: 7 H-trials, 7 K-trials, 7 S-trials, 7 C-trials, as well as 
4 nonoise trials (one of each letter). 
Trials are randomly chosen without replacement.

3 blocks make up 1 experimental session: 
Every combination of letter x spacing condition x noise condition is run once (combinations of 
noise condition 4 and 5 are run twice), 
H: 1(=noise condition)1(=spacing condition),12,13,21,22,23,31,32,33,41,42,43,41,42,43,51,52,53,51,52,53 
K: 11,12,13,21,22,23,31,32,33,41,42,43,41,42,43,51,52,53,51,52,53 
S: 11,12,13,21,22,23,31,32,33,41,42,43,41,42,43,51,52,53,51,52,53 
C: 11,12,13,21,22,23,31,32,33,41,42,43,41,42,43,51,52,53,51,52,53 

Balancing of the different letter rotations/selections of noise conditions 3 (selection), 4 (rotation), 5 (rotation) 
is achieved across all 6 experimental sessions (but not across a single experimental session).
This script runs all 6 experimental sessions in a row.

Each block.blocked runs 12 nonoise trials, 3 of each of the 4 target letters. Letters
are randomly sampled without replacement.

(E) TRIALS:
*Fixation Cross => press Space Bar to bring on target (and noise letters)
*target appears directly above Fixation Cross 
	(NOTE: Eriksen & Eriksen, 1974: 1/2 degree visual angle above,
	the location in this script is only a rough approximation and needs fine-tuning under EDITABLE VALUES)
*noise letters appear flanking the target (in noise trials),
type of noise letters depends on noise condition, spacing depends on spacing condition

Notes: 
* In Eriksen & Eriksen (1974) the target and noise letters remained on the screen for 1s (regardless of whether 
a response is given) and then disappeared together. In this script the response terminates the trial.
* In Eriksen & Eriksen (1974) error trials were repeated later in the session. In this script, error trials
are not rerun.

PRACTICE:
By default, three blocks of 32 trials are given as practice. Number can be edited under section EDITABLE VALUES.
During practice, participants receive feedback if they make a mistake.

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STIMULI
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target letters: H, K (angular), S, C (curved)

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INSTRUCTIONS 
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Instructions are not original and can be easily edited under section INSTRUCTIONS

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EDITABLE CODE 
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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:

Stimuli Sizing in mm:
/fontheight_inmm:						fontheight in cm (default: 0.5cm)
/screenheight: 							the height of the monitor that the experiment runs on
/fixed_distance_inmm:					the distance of the target stimuli from the fixation cross in mm (default is 10mm)
/spacing1_inmm:							the distance between stimuli in spacing condition 1 in mm (default is 3mm)
/spacing2_inmm:							the distance between stimuli in spacing condition 2 in mm (default is 10mm)
/spacing3_inmm:							the distance between stimuli in spacing condition 3 in mm (the default is 20mm)

Response Keys:
/leftkey:								left responsekey (default: "Q")
/rightke2:								right responsekey (default: "P")

Experimental Design:
/maxpracticeblocks:						determines how many practice blocks should be run (default: 3
										equivalent to one experimental session)
										
/trialtimeout:							the max. trial duration (in ms) (default: 1000ms)