Return to the Poffenberger Paradigm page
___________________________________________________________________________________________________________________
*POFFENBERGER PARADIGM*
___________________________________________________________________________________________________________________
Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com) for Millisecond Software, LLC
Date: 4-03-2013
last updated: 10-21-2019 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC
Script Copyright © 10-21-2019 Millisecond Software
___________________________________________________________________________________________________________________
BACKGROUND INFO
___________________________________________________________________________________________________________________
This script implements the Poffenberger Paradigm Task, a visual reaction time comparing crossed and
uncrossed information processing pathways:
Berlucchi, G., Heron, W., Hyman, R., Rizzolatti, G., & Umilta, C. (1971). Simple reaction times of ipsilateral
and contralateral hand to a lateralized visual stimulus. Brain, 94, 419–430.
___________________________________________________________________________________________________________________
TASK DESCRIPTION
___________________________________________________________________________________________________________________
Participants sit in front of a monitor screen (in Berlucchi et al, 1971: a domelike screen was used),
and are asked to press one key with either left or right hand when they detect a flash of light on the screen.
The flashes of light either appear on the left or right side of monitor. Depending on which hand is used
to respond, the reaction times are taken to reflect reaction times from uncrossed (e.g. left side & left hand) or
crossed pathways (e.g. left side & right hand).
In Berlucchi et al (1971), participants' left eyes were covered.
___________________________________________________________________________________________________________________
DURATION
___________________________________________________________________________________________________________________
the default set-up of the script takes appr. 30 minutes to complete
___________________________________________________________________________________________________________________
DATA FILE INFORMATION
___________________________________________________________________________________________________________________
The default data stored in the data files are:
(1) Raw data file: 'poffenbergerparadigm_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 such as feedback trials. Thus, trialnum
may not reflect the number of main trials run per block.
parameters.LatinSquareOrder: stores the LatinSquareOrder used for this participant
values.part: stores which part of the session is currently run (3 parts altogether)
values.rightleftorder: 1 = left ("nasal" for right eye) side first in a block;
0 = right side ("temporal" for right side) first in a block
values.responsehand_label: the assigned response hand (right or left)
values.crossed: 0 = not crossed;
1 = crossed (position and response hand crossed)
values.stim_x -values.stim_y: contains x/y coordinates of the current square
response: the participant's response (scancode of response button)
57 = spacebar
correct: the correctness of the response (1 = correct; 0 = incorrect)
latency: the response latency (in ms); measured from onset of square
values.validtrial: 1 = response latencies within latency boundaries (valid);
0 = response latencies outside latency boundaries (invalid -> trial will be repeated)
values.count_position1_left- tracks how often position 1(2, 3) left and right blocks have been run
values.count_position3_right
values.count_position1 - tracks how often position 1 to position 3 blocks have been run
values.count_position3
(2) Summary data file: 'poffenbergerparadigm_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)
parameters.LatinSquareOrder: stores the LatinSquareOrder used for this participant
expressions.ProcessingSpeed_difference: Difference between mean reaction time (in ms) of correct responses for crossed and uncrossed trials
(Note: Diff should be positive if crossed pathways take longer)
expressions.meanRT_uncrossed-
expressions.meanRT_crossed: mean reaction time (in ms) of correct responses for uncrossed and crossed trials
expressions.meanRT_pos1left_uncrossed-
expressions.meanRT_pos1right_crossed: mean reaction time (in ms) of correct responses for all position 1 combinations (position 1 = light flash closes to center)
(same for position 2 and 3)
expressions.meanRT_pos1_uncrossed-
expressions.meanRT_pos1_crossed: mean reaction time (in ms) of correct responses for position 1 uncrossed and crossed trials
(same for position 2 and 3)
___________________________________________________________________________________________________________________
EXPERIMENTAL SET-UP
___________________________________________________________________________________________________________________
(a) Design: 2 hands (right, left) x 2 stimulation sides (right, left side of screen) x 3 horizontal distances from the fixation point
(b) This script is set up to run this experiment over 3 different sessions (see Berlucchi et al, 1971)
see below (8) for more detailed information
(c) 3 sessions with 3 parts
(d) Each part: 4 blocks (position 1, 2, or 3 on one side), 4 blocks (same position on the other side)
=> it's randomly decided which part in a session presents which position with the constraint that over
the 3 experimental sessions, the presentation follows a Latin Square, so that each position occurs in each
part exactly once over the course of 3 sessions.
Example:
session 1: part 1 (presents position 1) - part 2 (presents position 2) - part 3 (presents position 3)
session 2: part 1 (presents position 2) - part 2 (presents position 3) - part 3 (presents position 1)
session 3: part 1 (presents position 3) - part 2 (presents position 1) - part 3 (presents position 2)
(e) block 1 & 4: same hand; block 2 & 3: opposite hand (randomly decided which hand goes first)
Example:
block.position1_left: L R R L ---- block.position1_right: R L L R
(it's randomly decided whether the left positions or the right positions are presented first)
uncrossed: hand and screen location the same (e.g. flash of light appears on left side, left hand responds)
crossed: hand and screen location are opposite (e.g. flash of light appears on the right side, left hand responds)
BLOCKS:
* Each block runs 15 trials
* if latencies are outside the boundaries of acceptable responses (Berlucchi et al (1971), p.421, set your own boundaries
under EDITABLE CODE -> Editable Values), the trial is declared invalid and will immediately get repeated.
TRIAL SEQUENCE:
a) Participants are presented a white fixation cross
b) after a set time, a sound is played (1000hz, 100ms duration, 0.2 Amplitude, created in Audacity),
signaling that the flash of light is soon to appear
c) flash of light appears and participants are asked to press the response key with the assigned hand.
___________________________________________________________________________________________________________________
INSTRUCTIONS
___________________________________________________________________________________________________________________
can be edited under EDITABLE Instructions
___________________________________________________________________________________________________________________
STIMULI
___________________________________________________________________________________________________________________
To fine-tune the stimulus size of the flashing light square and its 6 locations to your monitors,
go to section EDITABLE PARAMETERS and edit the following:
=> Coordinates of Light Square for three positions: EDITABLE CODE -> Editable Values
=> Size of Light Square: EDITABLE CODE -> Editable Values -> parameters.square_height
=> Contrast of Light Square to Background: adjust color under EDITABLE CODE -> Editable Stimuli -> shape.square
OPTIONAL SESSIONS #2 and #3
Berlucchi et al (1971) ran the experiment in three sessions. The distribution of stimulus location (3 different locations)
across the three parts in one session were randomly assigned with the constraint that the assignments
add up to a Latin Square across three sessions (= each location would appear in each part across all three sessions).
Assign the session ID at the start of the script.
/LatinSquareOrder = the value found in the participant's data file from the first session (e.g. 6)
these values together ensure the Latin Square assignment of locations to parts across 3 sessions.
___________________________________________________________________________________________________________________
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:
/LatinSquareOrder: stores the LatinSquareOrder
!!! NOTE: gets automatically assigned for first session; for subsequent sessions
fill in the LatinSquareOrder manually below
Physical Dimensions:
/square_height: sets the square height (default: 1% of the screen height)
/fixation_height: sets the height of the fixation cross (default: 5%)
Presentation Durations:
/squareduration: sets the duration of the square of light presentation (default: 32ms)
/fixationduration: sets the duration of the WHITE fixation cross (default: = 1000ms)
/posttrialpause adds a posttrialpause to the response trials for trial clean-up (default: 50ms)
Coordinates:
/Pos1_leftx: sets the x-coordinate of position 1 stimuli on the left (position 1 = closest to fixation)
/Pos2_leftx: sets the x-coordinate of position 2 stimuli on the left (position 2 = second closest to fixation)
/Pos3_leftx: sets the x-coordinate of position 3 stimuli on the left (position 3 = furthest from fixation)
/Pos1_rightx: same for stimuli on the right
/Pos2_rightx:
/Pos3_rightx:
Responsekeys:
/responsekey: scancode of responsekey (default: 57)
/responsekey_label: label of responsekey (default: "Spacebar")
Trial Details:
/initialtrialnumber: number of trials to run per block (if no repeats) (default: 15)
/practicetrialnumber: number of trials to run per practice block (if no repeats) (default: 5)
/anticipatoryresponse_position1: lower boundary for position 1 response latencies (default: 180ms)
/anticipatoryresponse_position2: lower boundary for position 2 response latencies (default: 190ms)
/anticipatoryresponse_position3: lower boundary for position 3 response latencies (default: 200ms)
/delayedresponse_position1: upper boundary for position 1 response latencies (default: 320ms)
/delayedresponse_position2: upper boundary for position 2 response latencies (default: 350ms)
/delayedresponse_position3: upper boundary for position 3 response latencies (default: 380ms)