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Representative Results






A Two-interval Forced-choice Task for Multisensory Comparisons

Published: November 9th, 2018



1Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México

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.

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.

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 inputs1,2,3. 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 ....

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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.......

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This protocol presented a method to perform a psychophysics experiment in humans. The technique replicated previous research on the discrimination of intervals of AP trains of V, A, and AV pulses, which was performed using a 2IFC method. The stimuli resulted from P and AP distributions of trains of six 50-ms pulses in different intervals within the range of milliseconds (i.e., from 500 ms to 1,100 ms in steps of 100 ms). Figure 2A shows some interval.......

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In psychophysics, the selection of a task depends on particular interests in perceptual phenomena5,6. 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,.......

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This work was supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT), CB-256767. The authors thank Isaac Morán for his technical assistance and Ana Escalante from the Computer Unit of the Instituto de Fisiología Celular (IFC) for her valuable assistance.


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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
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

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