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											DOT PROBE TASK
										Measure of Attentional Bias
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Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software LLC
Date: 11-28-2012
last updated:  11-08-2019 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC

Script Copyright © 11-08-2019 Millisecond Software

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BACKGROUND INFO 	
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This script implements a dotprobe procedure to measure attentional bias.
The implemented procedure is based on:

MacLeod, C. , Soong, L.Y., Rutherford, E., & Campbell, L.W. (2007). Internet-delivered assessment and manipulation 
of anxiety-linked attentional bias: Validation of a free-access attentional probe software package. 
Behavior Research Methods, 39, 533-538.

(the free-access attentional probe software package as well as the stimuli used is available under:
http://www.psy.uwa.edu.au/labs/cogemo/AttProbe1.html)

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TASK DESCRIPTION	
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After presentation of a fixation cross in the center of the screen, participants are presented with 
2 words from two categories (here: threat and neutral words). The position of the words is randomly
chosen to be either above or below the location of the fixation cross. After a short duration,
the two words disappear and a probe stimulus (here: < or >) appears in the location of one of the
words. Participants are asked to press one key if the probe is < and another if the probe is >.

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DURATION 
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the default set-up of the script takes appr. 6 minutes to complete

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

(1) Raw data file: 'dotprobe_macleod_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.
											
parameters.probetaskselection:			determines which type of dotprobe task to run
											1 = probe always in threat position
											2 = probe always in neutral position
											3 = probe randomly in threat or neutral position (half the time in threat position) (default)

parameters.randomprobe_x:			1 = the x-coordinate of the probe is randomly determined within the space that the 
											target previously occupied (see MacLeod et al, 2007); default
									2 = the probe is always presented at parameters.target_x (location of target)											
											
congruence:						1 = probe and target (threat) congruent; 2 = probe and target (threat) incongruent
targetlocation:					1 = target is displayed top (and comp is presented bottom); 2 = target is presented bottom (comp is presented top)
probeposition:					1 = probe is displayed on top; 2 = probe is displayed on bottom
probetype:						determines the type of the probe presented (1 vs. 2)

threat_y-probe_x:					the y-coordinate (in %) of the threat/neutral/probe (and x-coordinate of probe)
itemnumber						the itemnumber of the current word pair
threatword-neutralword:			contain the current stimuli
text.probe.currentitem:				current probe item

response:						the participant's response (scancode of response button): 18 vs. 23
correct:							accuracy of response (1 = correct; 0 = error)
latency: 							the response latency in ms (measured from onset of probe until response)


(2) Summary data file: 'dotprobe_macleod_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)

Task Parameters:
									
parameters.probetaskselection:				determines which type of dotprobe task to run
											1 = probe always in threat position
											2 = probe always in neutral position
											3 = probe randomly in threat or neutral position (half the time in threat position) (default)
											
parameters.fixationduration/targetduration:	the duration of the fixation crosses in ms (default: 500ms)/the targets (default: 500ms)

TP_ISI:							the interstimulus interval between offset of target and onset of probe in ms (default: 0)
probe_posttrialpause:				the interstimulus interval between offset of probe and begin of next trial in ms (default: 0)
probe1-probe2:					the symbols used for probe1 and probe 2 (default: >,<)

parameters.randomprobe_x:		1 = the x-coordinate of the probe is randomly determined within the space that the target previously occupied (see MacLeod et al, 2007); default
								2 = the probe is always presented at parameters.target_x (right above fixation)
								
Summary Variables:									
									
propcorrect:						overall proportion correct of all test trials
meanRT:							overall mean latency in ms of correct responses of all test trials

propcorrect_congruent:			proportion correct of all congruent test trials (congruent = target/threat and probe position congruent)
propcorrect_incongruent:			proportion correct of all incongruent test trials (congruent = target/threat and probe position incongruent)

meanRT_congruent:				mean latency in ms of correct congruent test trials
meanRT_incongruent:				mean latency in ms of correct incongruent test trials

TBI:								threat bias index calculated by subtracting the mean latency of responses to probes in threat positions (congruent)
								from mean latency of responses to probes in neutral positions (incongruent)
											Note: MacLeod et al (2007) use the medians instead of the means
								=>If positive: attentional bias towards threats words
								(the bigger the number, the higher the attentional focus on the threat words)

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EXPERIMENTAL SET-UP 
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2 target positions (up, down) x 2 target-probe congruence (congruent, incongruent) x 2 probe symbols, tested within participants

- 1 Block of 20 practice trials with digits; not original; practice trials give errorfeedback
- 1 Block of 96 trials
	- it can be set (see section Editable Values) whether 
			a) all the trials are threat-probe congruent
			b) all the trials are threat-probe incongruent
			c) 1/2 trials are congruent; 1/2 trials are incongruent (default)

- Default trialsequence: fixation (500ms)->targets(500ms)->TP_ISI(0ms)->Probe (until response) -> ISI (1000ms)
- stimuli pairs are randomly determined for each trial
- target positions/target-probe congruence/probe symbol randomly determined
- Probe can be right above the fixation cross or it is randomly placed in one of the previously occupied letter positions (default)
(can be set under section Editable Values)

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STIMULI
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This script uses the stimuli generously provided by MacLeod et al (2007) on their website (see above)
They can be edited under section Editable Stimuli
Probes can be edited under section Editable Parameters.

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INSTRUCTIONS 
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Instructions are not original to the task. They are provided by Millisecond Software
as htm/html pages and can be edited by changing the provided htm/html files.
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).

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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:

/probetaskselection:						1 = probe always in threat position (all probe-threat congruent)
										2 = probe always in neutral position (all probe-threat incongruent)
										3 = probe randomly in threat or neutral position (half the time in threat position) (default)
										
/fixationduration/targetduration:				the duration of the fixation crosses (default: 500ms)/the targets (default: 500ms)
/fixation_posttrialpause :					the posttrialpauses for the fixation crosses/the targets/the probe
/TP_ISI:									the interstimulus interval between offset of target and onset of probe in ms (default: 0)
/probe_posttrialpause:						the interstimulus interval between offset of probe and begin of next trial in ms (default: 0)
/probe1-probe2:							the symbols used for probe1 (E) and probe 2 (I)

/responsekey_probe1-
responsekey_probe2:						the keyboard scancodes associated with probe1 (default: 18, "E") and probe2 (default: 23, "I")
										as well as their respective labels
										
/letterheight:								the height of the letter in % of screen height (default: 5%)
											!!!NOTE: this script uses mono-spaced Lucinda Console as the default font;
											we suggest to not change the fontstyle as the calculation of the width of a single letter
											is based on this particular fontstyle.
											
/target_top_y-target_bottom_y:				the y-coordinate in % of the top/bottom target (default: 25%, 75%)
/target_x:								the x-coordinate of the target (default: center at 50%)

/randomprobe_x:							1 = the x-coordinate of the probe is randomly determined within the space that the 
											target previously occupied (see MacLeod et al, 2007); default
										2 = the probe is always presented at parameters.target_x (location of target)


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