Face in the Crowd Task

Technical Manual

Script Author: Millisecond Software, LLC

Last Modified: January 03, 2025 by K. Borchert (katjab@millisecond.com), Millisecond

Background

This script offers example code to 1) determine the relative coordinates of target locations (->block.determinecoordinates) 2) select locations in an image: FITC task (-> block.FITC)

The default is to run the FITC task. An editable variable (parameters.taskselection) can be set to run either task.

Duration

1 minute

Description

Participants are asked to select target faces in a picture depicting a crowd of people.

Procedure

Task: Determine The Relative Coordinates Of The Target Locations (->Block.Determinecoordinates)

1) Set your canvas under DEFAULTS. This is important as not all monitors are the same size.
Forcing a canvas on each monitor will keep the relative screen positions of the targets the same.

2) Force a picture size to ensure that the picture takes up the same relative canvas location on each monitor

3) create a trial that calculates the relative screen locations by using the x/y-coordinate of the mouse cursor at the end of the trial,
at the time of 'lButtonDown' (trial.determinecoordinates)
Stores the coordinates in the data file.

4) manually fill in the target coordinates into list.hposition and list.vposition under LISTS. Make sure that the index of the
coordinates corresponds to the index of the target image in item.targetfaces.
EXAMPLE: if the target image is 'Face03.jpg' and it is stored under index '/3 = "Face03.jpg"' in item.targetfaces
then make sure to store the corresponding coordinates as the third items in list.hposition and list.vposition

II) "Face in the Crowd" Task: FITC (-> block.FITC)

Task: Find Particular Faces In A Crowd

Steps:
1) Make sure the script runs the same /canvassize to run
block.FITC as was used to determine the target coordinates

2) The relative coordinates of the targets are used to define response circles (-> shape.responsecircle).
Check out shape.responsecircle for more details

3) Present these response circles BEFORE the crowd image, so that the crowd image covers response circles on the screen.
(FACE IN THE CROWD MAIN TRIALS-> trial.faceinthecrowd -> stimulusframes)
To check/debug the positions of the response circle: present the response circles AFTER the crowd image
(aka superimpose the circles onto the pictures)

4) Ask participants to click on the target faces in the crowd image. If they click on the underlying
response circles, the response is evaluated as 'correct'; if not the response is evaluated as 'incorrect'.

Summary Data

File Name: faceinthecrowd_demo_summary*.iqdat

Data Fields

Name	Description
inquisit.version	Inquisit version number
computer.platform	Device platform: win \| mac \|ios \| android
computer.touch	0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities
computer.hasKeyboard	0 = no external keyboard detected; 1 = external keyboard detected
startDate	Date the session was run
startTime	Time the session was run
subjectId	Participant ID
groupId	Group number
sessionId	Session number
elapsedTime	Session duration in ms
completed	0 = Test was not completed 1 = Test was completed
list.acc.mean	Overall proportion correct selections
list.rt.mean	Overall mean latency (in ms) of correct selections

Raw Data

File Name: faceinthecrowd_demo_raw*.iqdat

Data Fields

Name	Description
build	Inquisit version number
computer.platform	Device platform: win \| mac \|ios \| android
computer.touch	0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities
computer.hasKeyboard	0 = no external keyboard detected; 1 = external keyboard detected
date	Date the session was run
time	Time the session was run
subject	Participant ID
group	Group number
session	Session number
blockcode	The name the current block (built-in Inquisit variable)
blocknum	The number of the current block (built-in Inquisit variable)
trialcode	The name of the currently recorded trial (built-in Inquisit variable)
trialnum	The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file.
target	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)
percentHorizontalTargetx	Stores the percent (of canvas) of the horizontal target coordinate
percentVerticalTargety	Stores the percent (of canvas) of the vertical target coordinate
percentResponseX	Stores the percent (of canvas) of the x coordinate of the response
percentResponseY	Stores the percent (of canvas) of the x coordinate of the response

Parameters

The procedure can be adjusted by setting the following parameters.

Name	Description	Default
taskSelection	1 = determine coordinates of the targets and have the coordinates saved as screen percentages in the datafile 0 = run the task of finding the faces the crowd (FITC) (default)	0