Psychological Refractory Period Task

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond

Created: January 22, 2013

Last Modified: January 01, 2024 by K. Borchert (katjab@millisecond.com), Millisecond

Script Copyright © Millisecond Software, LLC

Background

This script implements the Psychological Refractory Period (PRP) Task by Marczinski & Fillmore (2006). The PRP task is a dual reaction time task, requiring participants to perform a task1 before performing a task2 during each trial. Typically, responses to task1 interfere with responses to task2 as expressed by delayed response times to task2. According to Marczinski & Fillmore (2006) this delay is attributed to the psychological refractory period which refers to the time period during which task1 is still being processed and task2 cannot be processed yet. The interference effect is particularly sensitive to disruptions of alcohol.

References

Marczinski, C.A. & Fillmore, M.T. (2006). Clubgoers and Their Trendy Cocktails: Implications of Mixing Caffeine Into Alcohol on Information Processing and Subjective Reports of Intoxication. Experimental and Clinical Psychopharmacology, 14, 450–458.

Millisecond thanks Dr. Fillmore for graciously reviewing this script and giving us ample feedback!

Duration

15 minutes

Description

DUAL TASK; temporally separated by randomly selected stimulus onset asynchronies (SOA). Task1: go-nogo task. Press the ENTER* key with your right hand (index finger) as soon as you see a "1" (go), don't do anything with your right hand if you see an "X" (nogo) • original task used "1" key on numeric keypad Task2: auditory discrimination task. Press "a" with your left hand (middle finger) when you hear a high sound; press "z" with your left hand (index finger) when you hear a low sound.

The response to Task 1 (if one is given) should be given before response to Task 2 - as a response to task 2 terminates the trial.

A PRPInterferenceScore calculates the interference score by subtracting the mean rt times (task2) for maximum SOAs (low interference) from the mean rt times (task 2) for minimum SOAs (high interference). Incorrect responses (responses that were either incorrect for task 1 or task 2 or both) as well as responses that were faster than 100ms and slower than 2000ms were filtered out as recommended by Dr. Fillmore.

Procedure

EXPERIMENTAL DESIGN (see Marczinski & Fillmore, 2006)
• 2 (types of task 1 stimuli) x 2 (types of task 2 stimuli) x 4 (SOAs) * 12 repetitions = 192 trials
=> each combination of task stimuli (= 4 combinations) are paired with 12 sets of the 4 SOAs

SEQUENCE OF TRIAL EVENTS:
1. fixation cross appears for 250ms (default, editable value)
2. a blank screen is presented for a randomly determined time period
(list.foreperiodduration contains default values)
3. task 1 stimulus appears in the middle of the screen (response to task 1 stimulus can be given as soon as
stimulus appears on the screen; reaction time to task 1 is measured from onset of task 1 stimulus);
task 1 stimulus disappears after 2000ms (default, editable value) or when response to task 2 is given
4. after a randomly sampled SOA, the task 2 stimulus is presented (response to task 2 stimulus can be given as
soon as task 2 stimulus appears on the screen; reaction time to task 2 is measured from onset of task 2 stimulus);
task 2 stimulus was presented for 500ms.
5. after participant responds to task 2 stimulus or after 2000ms of onset of task 2 stimulus (default, editable value),
whichever comes first, the intertrialperiod of 2200ms is started. Error Feedback is given during this
time.

PRACTICE:
Practice is given twice, once to give participants an opportunity to learn about the tasks and the stimuli and once
to assess whether PRP interference (likely) occurs. The first set of practice trials (20 trials) gives
complete feedback (correct, incorrect, no response detected). The second set of practice trials (20 trials)
is presented like the actual test with only error feedback/no response detected. After the second practice set,
the PRP index score is presented and the experimenter can decide to continue on to the actual test
or repeat practice.

Stimuli

TASK 1: go stimulus = "1" and nogo stimulus = "X" (see Marczinski & Fillmore, 2006).
The default response key for the go stimulus is the ENTER key (scancode 28, editable value). This differs from
Marczinski & Fillmore (2006) as they used the "1" key on the numeric key pad on the right side of the keyboard.
In order to run this experiment on keyboards that do not have the numeric keypad on the right, a different response
key is used in this script.

TASK 2: low tone (125 Hz) ; high tone (1000hz), both 500ms long (see Marczinski & Fillmore, 2006);
the stimuli are NOT originals.
The stimuli for this script were created in Audacity.
The low tone was created with an amplitude of 0.8 (125Hz, 500ms);
the high tone was created with an amplitude of 0.1 (1000Hz, 500ms).
The default keyboard response keys are "a" for high tone and "z" for the low tone (this combination is chosen due
to the fact that they both appear on the left and side of the keyboard with "a" sitting above (=high) "z" (=low)

Instructions

Instructions are not original but based heavily original instructions kindly provided by Dr. Fillmore.
Instructions are provided by Millisecond
as htm/html pages and can be edited by changing the provided htm/html files.
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).

Summary Data

File Name: psychologicalrefractoryperiod_summary*.iqdat

Data Fields

Raw Data

File Name: psychologicalrefractoryperiod_raw*.iqdat

Data Fields

Parameters

The procedure can be adjusted by setting the following parameters.