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									GLOBAL LOCAL TASK - NAVON TASK
SCRIPT INFO

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date: 10-30-2013
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 Global Local Task as described in:

Navon, D. (1977). Forest Before Trees: The Precedence of Global Features in Visual Perception.
COGNITIVE PSYCHOLOGY, 9, 353-383.(Experiment3)

											  *Task*
Participants are briefly presented with letter shapes (e.g. H or S) that are made up of little
letter shapes (e.g. H or S). Some of these letters have the same global (overall shape) and 
local (individual building shapes) letters (e.g. an H that consists of Hs), and some have 
different global and local letters (e.g. an H that consists of Ss). In the global condition
participants are asked to respond to the global shape of the letter (e.g. press key H if the
global shape of the letter is an H regardless of individual building blocks); 
in the local condition participants are asked to respond to the local shapes of the letter 
(e.g. press H if the local building elements are Hs regardless of overall shape). 



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

(1) Raw data file: 'GlobalLocalTask_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 subjectnumber
								(group: 1 = global->local; 2 = local->global)
blockcode, blocknum:			the name and number of the current block
/countblocks_global:			counts the number of global blocks
/countblocks_local:				counts the number of local blocks
trialcode, trialnum: 			the name and number of the currently recorded trial
								(Note: not all trials that are run might record data) 
/phase:							"practice" vs. "test" 
									Note: by default 2 (parameters.numberpracticeblocks) blocks in each condition are
									practice blocks
/condition:						1 = Global; 2 = Local									
/quadrant:						stores the currently selected quadrant the stimulus is presented in
/consistency:					"consistent": global and local shapes are consistent (e.g. an H made of little Hs)
								"conflicting": global and local shapes are conflicting (e.g. an H made of little Ss)
								"neutral": global and local shapes are inconsistent but not conflicting as one element
											("O") has no response button attached to it (e.g. an H made of little "Os")
/stimulus:						stores the name of the current stimulus picture
/stimulusitem:					the first stimulus presented in a trial
/target:						'S' or 'H'
response:						the participant's response
correct:						the correctness of the response
latency: 						the response latency (measured from onset of stimuli; in ms)

(2) Summary data file: 'GlobalLocalTask_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)

/meanRT_consistent_global-
/meanRT_neutral_local:			mean latency (in ms) of correct responses to the 6 different conditions


EXPERIMENTAL SET-UP:
-2 conditions (global vs. local) tested within. Order is counterbalanced by groupnumber.
-3 consistencies (consistent vs. neutral vs. conflicting): 
		global and local shapes the same (congruent); 
		global and local shapes different (incongruent)
		neutral = control condition

*Blocks:
- per condition: 6 blocks of 36 trials  
	=> by default, the first 2 blocks of each condition are considered practice blocks
	=> altogether 8 test blocks of 36 trials = 288 trials total
- the 6 stimuli per condition (global: overall shapes S and H only; local: building elements S and H only) are presented
	6 times (random selection)
- the stimuli can be either presented randomly in any of the 4 screen quadrants (default) or in the center of the screen 
	(if random; the four different screen quadrants that the stimuli can be presented in are randomly selected 9 times each.)

*Trial Sequence:
Beep (50ms) + Fixation Cross (500ms) -> Stimulus (parameters.stimulusduration) -> mask until response -> ITI: 3s
Latencies are measure from onset of stimulus. Participants are instructed to press either S or H.

STIMULI
A)Letter Stimuli
- The letter stimuli used in this script were generated by Millisecond Software with the help of PowerPoint and
Paint.Net. 
	=> The height of the global shape = 7* the height of the individual local shapes
	=> The width of the global shape = 6* the width of the individual local shapes
There are 9 different stimuli: 3 global shapes (H, S, "O"*) and 3 local shapes (H, S, "O").
You are welcome to use these stimuli or substitute your own under 
section Editable Stimuli -> item.stims

* the actual shape was supposed to be a rectangle but Navon (1977) notes that it was referred to as an "O"
by participants

-Size of the Letters: the size of the letter stimuli can be fine-tuned for a particular display under
section Editable Parameters -> parameters.picturesize

B) Beep:
the beep was produced in Audacity

INSTRUCTIONS
This script provides general instruction slides that are not original. Instruction slides
can be easily changed for customized ones under
EDITABLE CODE -> Editable Instructions -> item.instructionslides


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:

/responsekey1:							scancode of the first response key (default: 35)
											Note: scancodes under Tools -> Keyboard Scancodes
/responsekey_label1:					label of the first response key (default: "H")
/responsekey2:							scancode of the second response key (default: 31)
											Note: scancodes under Tools -> Keyboard Scancodes
/responsekey_label2:					label of the second response key (default: "S")

/picturesize:							height of the targets in screen height percentages (default: 20%)
											Notes: 		- Stimuli used in Experiment 3 were the same as in Experiment 2 - small size condition (Navon, 1977, p.369)
														- 'The size of the whole stimulus was the same as in Experiment 1' - small size condition (Navon, 1977, p.365)
														- 'The longest vertical diameter of each of the visual stimuli was 28 mm' (50cm viewing distance) (Navon, 1977, p.362)										
/fontsize_fixation:						fontsize of the fixation mark in screen height percentages (default: 10%)

/stimulusduration:						presentation duration of the targets 
											Note: the original study (Navon, 1977) used an oscilloscope with a presentation time of 40ms.
											This script adapts the procedure to the computer and increases the presentation time
											(default: 100ms)
/fixationduration:						presentation duration of the fixation stimulus (default: 500ms)
/iti:									intertrialinterval (default: 3000ms)
/restduration:							duration of the resttrial after each block (default: 20000ms)

/numberofpracticeblocks:				the number of blocks in each condition that count as practice.
										Navon (1977) used the first 2 blocks in each condition as practice blocks.
/randomtargetlocation:					true = target is presented randomly in any of the four screen quadrants; 
											the four different screen quadrants that the stimuli can be presented in are randomly selected 9 times each. (default)
										false = target is presented in the center of the screen

Quadrant screen coordinates:			Navon (1977, p.369): "The distance between the center of any of the stimuli and the fixation point was 24 mm."
/xpos1 = 25%					
/xpos2 = 75%
/ypos1 = 25%
/ypos2 = 75%

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