Return to the Police Officer's Dilemma Task page

Script Author: Katja Borchert, Ph.D. ( for Millisecond Software LLC
Date: 04-12-2012
last updated: 01-21-2016 by K.Borchert ( for Millisecond Software LLC

Copyright © 01-21-2016 Millisecond Software


This script provides the Police Officer Dilemma Task (PODT)  as described in (Experiment1):

Correll, J., Park, B., Judd, C.M., & Wittenbrink, B. (2002). The Police Officer's Dilemma:
Using Ethnicity to Disambiguate Potentially Threating Individuals. Journal of Personality 
and Social Psychology, 83, 1314-1329.

All images used in this script are the originals. Millisecond Software thanks Dr. Correll et al for
providing generous assistance!

Participants see a series of men, either White or Black, that either hold harmless objects or guns, 
and have to decide -within a short timeframe- whether to 'shoot' (if there is a gun) or not to 'shoot' (no gun present).
'Shooting' is done via response button presses.
Before each target appears, participants see a varying number of backgrounds. 
The targets (men with objects) appear in the last background shown. 

The default data stored in the data files are:

(1) Raw data file: 'PODT_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; by default data is collected unless /recorddata = false is set for a particular trial/block) 
itemnumber:						determines the itemnumber of the target image
selectbackground:				determines which background picture is selected
repetition:						determines how many background images are to be  presented
backgroundduration:				determines how long each background slide is presented
count_background:				counts how many background slides have been presented

response:						the participant's response
correct:						the correctness of the response (1 = correct; 0 = incorrect)
result:							either "Hit", "Miss", "CR", "FA" or "Noresponse"
latency: 						the response latency (in ms)
total:							keeps a running tab of the total money earned (or lost)

(2) Summary data file: 'PODT_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)
/countObjectBlack:		        counts the trials in each of the 8 conditions
/SumBlackCRs:					keeps a running total of Hits, Misses, FAs, CRs for each ethnicity
/MeanRT_BlackCRs:				the mean reaction times for Hits, Misses, FAs, CRs for each ethnicity (in ms)
/percent_BlackCRs:				the percentages of Hits-Misses and CRs-FAs, separately for each ethnicity

Design: 2 (ethnicity: black vs. white) x 2 (gun vs. no gun) = 4 experimental conditions, 
all tested within participants in a mixed design (see Correll et al, 2002)

1 Practice Block: 20 trials
1 Test Block: 80 Trials, 20 trials in each of the 4 conditions, conditions are randomly sampled without replacement (see list.condition for details)
(shoot keys are counterbalanced by groupnumber)
- Number of background images in background slideshow: randomly  (with replacement) determined, between 1-4 (see list.repetition) (-> Correll et al, 2002)

Trials Sequences: 
Fixation (500ms)-> Background (variable number) (500-1000ms)-> target (850ms)-> Feedback (3000ms)

original pictures; editable under section Editable Stimuli

Instructions easily adaptable under section Editable Instructions. Current Instructions modelled after
the latest instructions used by Correll et al (these later instructions are 
less detailed than the original 2002 instructions)

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:

HitReward....FAPunish: 					amounts earned or lost depending on Hits, Misses, Correct Rejections (CR), False Alarms (FA)
fixationduration:						the duration of the fixation cross in ms (default: 500, original)
key1/key2:								the scancodes of the shoot and noshoot keys (keys are counterbalanced), default: "A" and "L"
key1_label/key2_label:					the default labels for the response keys
timeout:								timeout of main experimental trials in ms, default = 850ms
feedbackduration:						the duration of the feedback in ms, default = 3000

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