Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: April 03, 2013
Last Modified: January 07, 2025 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
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.
30 minutes
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.
(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.
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.
can be edited under EDITABLE Instructions
File Name: poffenbergerparadigm_summary*.iqdat
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| 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 |
| parameters- LatinSquareOrder | Stores the LatinSquareOrder used for this participant |
| processingSpeedDifference | Difference between mean reaction time (in ms) of correct responses for crossed and uncrossed trials ( Diff should be positive if crossed pathways take longer) meanRTUncrossed- |
| meanRTCrossed | Mean reaction time (in ms) of correct responses for uncrossed and crossed trials meanRTPos1LeftUncrossed- |
| meanRTPos1RightCrossed | 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) meanRTPos1Uncrossed- |
| meanRTPos1Crossed | Mean reaction time (in ms) of correct responses for position 1 uncrossed and crossed trials (same for position 2 and 3) |
File Name: poffenbergerparadigm_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockCode | Name of the current block |
| blockNum | Number of the current block |
| trialCode | Name of the current trial |
| trialNum | Number of the current trial |
| parameters- LatinSquareOrder | Stores the LatinSquareOrder used for this participant |
| part | Stores which part of the session is currently run (3 parts altogether) |
| rightLeftOrder | 1 = left ("nasal" for right eye) side first in a block 0 = right side ("temporal" for right side) first in a block |
| responseHandLabel | The assigned response hand (right or left) |
| crossed | 0 = not crossed 1 = crossed (position and response hand crossed) |
| stimX - stimY | 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 |
| validTrial | 1 = response latencies within latency boundaries (valid) 0 = response latencies outside latency boundaries (invalid -> trial will be repeated) |
| countPosition1Left- | Tracks how often position 1(2, 3) left and right blocks have been run countPosition3Right |
| countPosition1 - | Tracks how often position 1 to position 3 blocks have been run countPosition3 |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| latinSquareOrder | Stores the LatinSquareOrder !!! gets automatically assigned for first session; for subsequent sessions fill in the LatinSquareOrder manually below Physical Dimensions | |
| squareHeight | Sets the square height | 1% of the screen height |
| fixationHeight | Sets the height of the fixation cross Presentation Durations | 5% |
| squareDuration | Sets the duration of the square of light presentation | 32ms |
| fixationDuration | Sets the duration of the WHITE fixation cross | = 1000ms |
| posttrialPause | Adds a posttrialpause to the response trials for trial clean-up coordinates | 50ms |
| pos1Leftx | Sets the x-coordinate of position 1 stimuli on the left (position 1 = closest to fixation) | |
| pos2Leftx | Sets the x-coordinate of position 2 stimuli on the left (position 2 = second closest to fixation) | |
| pos3Leftx | Sets the x-coordinate of position 3 stimuli on the left (position 3 = furthest from fixation) | |
| pos1Rightx | Same for stimuli on the right | |
| pos2Rightx | ||
| pos3Rightx | responseKeys | |
| responseKey | Responsekey (default: " " -> spacebar Trial Details | |
| initialTrialNumber | Number of trials to run per block (if no repeats) | 15 |
| practiceTrialNumber | Number of trials to run per practice block (if no repeats) | 5 |
| anticipatoryResponsePosition1 | Lower boundary for position 1 response latencies | 180ms |
| anticipatoryResponsePosition2 | Lower boundary for position 2 response latencies | 190ms |
| anticipatoryResponsePosition3 | Lower boundary for position 3 response latencies | 200ms |
| delayedResponsePosition1 | Upper boundary for position 1 response latencies | 320ms |
| delayedResponsePosition2 | Upper boundary for position 2 response latencies | 350ms |
| delayedResponsePosition3 | Upper boundary for position 3 response latencies | 380ms |