A Two-interval Forced-choice Task for Multisensory Comparisons

Summary

Psychophysics is essential for studying perception phenomena through sensory information. Here we present a protocol to perform a two-interval forced-choice task as implemented in a previous report on human psychophysics where participants estimated the duration of visual, auditory, or audiovisual intervals of aperiodic trains of pulses.

Abstract

We provide a procedure for a psychophysics experiment in humans based on a previously described paradigm aimed to characterize the perceptual duration of intervals within the range of milliseconds of visual, acoustic, and audiovisual aperiodic trains of six pulses. In this task, each of the trials consists of two consecutive intramodal intervals where the participants press the upward arrow key to report that the second stimulus lasted longer than the reference, or the downward arrow key to indicate otherwise. The analysis of the behavior results in psychometric functions of the probability of estimating the comparison stimulus to be longer than the reference, as a function of the comparison intervals. In conclusion, we advance a way of implementing standard programming software to create visual, acoustic, and audiovisual stimuli, and to generate a two-interval forced-choice (2IFC) task by delivering stimuli through noise-blocking headphones and a computer's monitor.

Introduction

The purpose of this protocol is to convey a procedure for a standard experiment on psychophysics. Psychophysics is the study of perception phenomena through the measure of behavioral responses, elicited by sensory inputs^1,2,3. Usually, human psychophysics is an inexpensive and essential tool to implement in imaging or neurophysiological experiments⁴. However, it is never easy to select the most appropriate psychophysical method out of many that exist, and the selection somewhat depends on experience and preference. Nevertheless, we encourage beginners ....

Protocol

The experiments were approved by the Bioethical Committee of the Institute of Cellular Physiology of UNAM (No. CECB_08) and carried out under the guidelines of The Code of Ethics of the World Medical Association.

1. Experimental Set-up

1. Material and stimuli set-up for performing an aperiodic interval discrimination (AID) task
   1. Perform this experiment on a computer with a minimum of 8 GB RAM, 2.5 GHz processor, and a 60 Hz refreshing rate monitor to create.......

Discussion

In psychophysics, the selection of a task depends on particular interests in perceptual phenomena^5,6. For instance, this protocol consisted of recreating a previously reported paradigm on the time-interval perception of visual, auditory, and audiovisual stimuli of aperiodically arrayed pulses, which implemented the 2IFC method¹³. Here, as in most of the psychophysics tasks, adequate hardware and software are essential to create, reproduce,.......

Materials

Name	Company	Catalog Number	Comments
Lapt top Dell Precision	Dell	M6800 CTO	Procesador Intel Core i7-4710MQ, 2.5GHz RAM 16 GB, 64-bit OS; 17.3" screen 1920 x 1080; 60 Hz refreshing rate
Noise-blocking headphones	Bose	QC25	Headphones QuietComfort 25, noise-blocking
Decibel meter	Extech Instruments	SL 130G	Sound Level meter (dB), range 30 to 130 dB, this meter meets ANSI and IEC Type 2 sound level meter standards
Name	Company	Catalog Number	Comments
Software
Labview	National Instruments	Labview 2014	Labview SP1 130, 64-bits, version 14
Matlab	Mathworks Inc	Matlab 2016a	The Mathworks Inc., Natick, MA, USA
GUI To create Visual and Acoustic stimuli. Created by Fabiola Duarte	Mathworks Inc	Matlab 2016a	The Mathworks Inc., Natick, MA, USA