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										ERIKSEN FLANKER TEST
SCRIPT INFO

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date:  09-19-2012
last updated: 01-11-2016 by K.Borchert (katjab@millisecond.com) for Millisecond Software LLC

Copyright © 01-11-2016 Millisecond Software


BACKGROUND INFO

											*Purpose*
This script implements the Flanker Task described in 

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.


											  *Task*
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


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

(1) Raw data file: 'FlankerTest_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, 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)
/trialcount:					counts the number of trials
/responsecondition:				counterbalanced response key condition
/noisecondition:				stores the current noise condition (1-5)
/spacingcondition:				stores the current spacing condition (1-3)
/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:					the presented stimuli in order of trial presentation
response:						the participant's response
correct:						the correctness of the response
latency: 						the response latency (in ms)

(2) Summary data file: 'FlankerTest_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; 1 = script was completed (all conditions run)
/properror_noise1-
/properror_noise5:				error proportion, separately for each noise condition

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

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

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

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

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


EXPERIMENTAL SET-UP:

(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_incm)
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).

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

Note: 
* 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. That's the default in this script.  
If targets and noise should disappear immediately  after a response is given, go to TRIALS and follow instructions.

Note:
* 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.

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

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

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:

/fontheight_incm:						fontheight in cm (default: 0.5cm)
/screenheight: 							the height of the monitor that the experiment runs on
/fix_distance:							the distance of the target stimuli from the fixation cross in cm 
										(default is 1cm)
/spacing1:								the distance between stimuli in spacing condition 1 in cm
										(default is 0.03cm)
/spacing2:								the distance between stimuli in spacing condition 2 in cm
										(default is 1cm)
/spacing3:								the distance between stimuli in spacing condition 3 in cm
										(the default is 3cm)
/key1:									scancode of responsekey 1 (default: 16, "q"), if change, also change label
/key2:									scancode of responsekey 2 (default: 25, "p")
/key1label:								the label of responsekey 1 (used in instructions)
/key2label:								the label of responsekey 2 (used in instructions)
/maxpracticeblocks:						determines how many practice blocks should be run (default: 3
										equivalent to one experimental session)

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