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										CHANGE BLINDNESS

SCRIPT INFO

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date: 09-13-2013
last updated:  01-06-2016 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC

Copyright ©  01-06-2016 Millisecond Software


BACKGROUND INFO

											*Purpose*
This script implements the change blindness paradigm as described in:
Beck, M.R. & Levin, D.T (2003). The role of representational volatility in recognizing pre- and postchange objects. 
Perception & Psychophysics, 65, 458-468.


											  *Task*
Participants are presented a 'before' and an 'after' picture for 2s. Each picture consists of 3-16 different objects that
are arranged in a 4x4 matrix. One object is changed from the 'before' to the 'after' picture. In two recognition tasks
participants are asked to select a) the prechange object and b) the postchange objects out of 4 possible choices. 
The order of the tasks is counterbalanced between participants.


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

(1) Raw data file: 'ChangeBlindness_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) 
/expcondition:					1 = prechange Forced Choice Task before postchange Forced Choice Task
								2 = postchange Forced Choice Task before prechange Forced Choice Task
/shift:							1 = right shift of coordinates for postchange presentation; 
								2 = left shift of coordinates for postchange presentation
/numberofobjects:				stores the current number of objects in the array
/arraypresentationtime:			current arraypresentation time
stimulusitem:					the presented stimuli in order of trial presentation (may not coincide with screen position)
response:						the participant's response
correct:						the correctness of the response
latency: 						the response latency in ms

/array_itemnumbers:				string variable that stores all the itemnumbers of the selected array objects
/prechangeobject:				contains the itemnumber of the prechanged object (= same as object1)
/postchangeobject:				contains the itemnumber of the postchanged object
/prefoilobject:					contains the itemnumber of the prefoil object (= same as object2) in prechange lineup
/postfoilobject:				contains the itemnumber of the postfoil object (= same as object3) in postchange lineup
/pre_unrelatedobject1:			contains the itemnumber of a totally new object in prechange lineup
/pre_unrelatedobject2:			contains the itemnumber of a totally new object in prechange lineup
/post_unrelatedobject1:			contains the itemnumber of a totally new object in postchange lineup
/post_unrelatedobject2:			contains the itemnumber of a totally new object in postchange lineup
/object1-
/object16:						stores the itemnumber of object1 to object16 (screen locations randomly determined)

(2) Summary data file: 'ChangeBlindness_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)
/expcondition:						1 = prechange Forced Choice Task before postchange Forced Choice Task
									2 = postchange Forced Choice Task before prechange Forced Choice Task
/practice_arraypresentationtime:	sets the object array presentation time during practice (default: 3000ms)
										Note: a practice session wasn't mentioned in the original article
/test_arraypresentationtime:		sets the object array presentation time during testing (default: 2000ms)
										Note: could also be declared as a list in case different test_arraypresentationtimes = IV

/array_ISI:							(interstimulus) time between offset of 'before' array and onset of 'after' array (default: 350ms) in ms
/4AFC_ISI:							time between the two recognition tasks (default: 500ms) in ms
/ITI:								(intertrial) time between end of 2nd recognition task and onset of next 'before' array (default: 1000ms) in ms
/prechange_hits-
/postchange_FAs:					sums up hits/False Alarms (FAs) for prechange and postchange recognition
/prechange3_diff: 					difference in values.prechange_hits - values.prechange_FAs for array number = 3 (same for all array numbers)
/postchange3_diff:					difference in values.postchange_hits - values.postchange_FAs for array number = 3 (same for all array numbers)


EXPERIMENTAL SET-UP
* 'before' and 'after' picture: consist of 3-16 objects, randomly arranged in a 4x4 matrix ('after' picture is slightly
shifted to the left or right by default) => one object changes from the 'before' to the 'after' picture
* order of recognition tasks (prechange picture -> postchange picture) is counterbalanced by groupnumber
* recognition tasks present: one foil (a different one for each task), the target item (prechange object or postchange
object, 2 unrelated objects (different ones for each task); the order of the objects is randomly determined
* by default half the 'after' pictures are shifted to the left, the other half to the 'right' (randomly determined)
* Test Block: 14 different array objects (3-16) * 4 repetitions = 56 trial sequences
*optional practice block: 10 practice trials with number of array objects = 4 and with error feedback (it is run by default);
array presentation times can be increased (default) from testing session.

STIMULI
The images provided with this script are digitalized versions (300px x 300px) of the pictures presented by:
Snodgrass, J. G., & Vanderwart, M. (1980). A standardized set of 260 pictures: Norms for name agreement, 
image agreement, familiarity, and visual complexity. Journal of Experimental Psychology:
Human Learning & Memory, 6, 174-215.

The images were created in Paint.NET by Millisecond Software LLC.


INSTRUCTIONS
not original; can be edited under section EDITABLE 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:

Durations:
/runpracticeblock:								true = runs a practice block (see block.practice under BLOCKS) - default option
												false = skips the practice block (!!!Instructions need to be updated accordingly)

/practice_arraypresentationtime:				sets the object array presentation time during practice in ms (default: 3000ms)
													Note: a practice session wasn't mentioned in the original article
/test_arraypresentationtime:					sets the object array presentation time during testing in ms (default: 2000ms)
													Note: could also be declared as a list in case different test_arraypresentationtimes = IV

/array_ISI:										(interstimulus) time in ms between offset of 'before' array and onset of 'after' array (default: 350ms)
/4AFC_ISI:										time between the two recognition tasks (default: 500ms)
/ITI:											(intertrial) time in ms between end of 2nd recognition task and onset of next 'before' array (default: 1000ms)


4x4 Matrix Presentation:
/pictureheight:									sets the picture size in canvas height percentages
/column1_x -
/row4_y:										sets the picture center (in %) for the 4columns/4rows for 'before' picture 
/shiftpercent:									determines how much the after picture should be shifted to right/left (default: 10% = 1/2 column width)

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