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==Notes on the McGurk Stimuli==
==Notes on the McGurk Stimuli==


The McGurk-MacDonald effect is an audiovisual illusion. Here are some audiovisual files that can be used to demonstrate the effect.
The McGurk-MacDonald effect is an audiovisual illusion. Here are some audiovisual files that can be used to demonstrate the effect. McGurk stimuli consist of an auditory syllable and an incongruent visual syllable that produce the percept of a different syllable (e.g. auditory "ba" + visual "ga" perceived as "da"). Other incongruent stimuli (e.g. auditory "ga" + visual "ba") do not produce the effect. Here is an archive of some the stimuli used in our publications, referenced in [[Beauchamp:Publications]].
McGurk stimuli consist of auditory syllables and an incongruent visual syllable that produced the percept of a different syllable (e.g. auditory "ba" + visual "ga" perceived as "da").
[[Media:McGurkAndControlStimuli.zip|McGurk and Other Stimuli Archive]]


Farnsworth-Munsell 100 Hue test is a behavioral test of color vision.
Note that some of these files require a particular video codec that is freely available in the VLC player, available from
http://www.videolan.org/vlc/


It was adapted for use in the fMRI scanner as described in
To see the stimuli on any platform, you may view them on YouTube
#Beauchamp, M.S., Haxby, J.V., Jennings, J.E., and DeYoe, E.A.: An fMRI version of the Farnsworth-Munsell 100-Hue test reveals multiple color-selective areas in human ventral occipitotemporal cortex. Cereb Cortex 9: 257-263, 1999. [[Media:BeauchampCerCor99.pdf|Click here to download the PDF. ]][[Media:BeauchampCerCor99Cover.pdf|Click here for the related journal cover image]]
#Auditory "ba" + Visual "ga" --> AV "da"  http://www.youtube.com/watch?v=WK3T7LWIkP8
# Beauchamp, M.S., Haxby, J.V., Rosen, A.C., and DeYoe, E.A.: A functional MRI case study of acquired cerebral dyschromatopsia. Neuropsychologia 38:1170-1179, 2000. [[Media:BeauchampNeuropsychologia2000.pdf|Click here to download the PDF]]
#Auditory "pa" + Visual "ka" --> AV "ta" http://www.youtube.com/watch?v=An5vvn-gcwA


In these publications, stimuli was presented using a Cambridge Research Systems graphics board. Each color was calibrated to be the same brightness as every color using flicker photometry. This is important because the F-M 100 Hue test requires subjects to place the colors in order by hue. If the colors differ in brightness, subjects could "cheat" and use brightness as a cue.
See also
However, equating brightnesses is time-consuming.
[[Beauchamp:Stimuli]] for other McGurk YouTube examples.
Therefore, the fMRI adaptation was further adapted to eliminate the brightness matching step as described in


# Simmons, W. K., Ramjee, V., Beauchamp, M. S., McRae, K., Martin, A., and Barsalou, L. W.: A common neural substrate for perceiving and knowing about color. Neuropsychologia 45:2802-2810, 2007. [[Media:SimmonsetalNeuropsychologia2007.pdf|Click here to download the PDF]]
==Single-syllable audiovisual words==
Please cite
# Nath, AR and Beauchamp, MS. A Neural Basis for Interindividual Differences in the McGurk Effect, a Multisensory Speech Illusion. Neuroimage. 2012 59:781-787.
# Nath, AR, Fava EE and Beauchamp, MS. Neural Correlates of Interindividual Differences in Children's Audiovisual Speech Perception. Journal of Neuroscience. 2011 Sept 28;31(39)13963-13971.


These stimuli consist of JPGs of colored and black and white stimuli. To localize color-selective areas, present separate blocks of colored stimuli and black-and-white stimuli, one stimulus every two to three seconds; a brief interstimulus interval (500 ms was used in Cerebral Cortex article above) is also a good idea. Twenty second blocks of stimulation interspersed with 10 seconds of fixation could work reasonably well.
The following is from the methods section of Nath and Beauchamp (2012):
Click here to download a .zip file of the stimulus archive
 
[[Media:Beauchamp100HueStimuli.zip|Beauchamp100HueStimuli|]]
Word stimuli for the localizer were selected from two hundred single-syllable words from the MRC Psycholinguistic Database with Brown verbal frequency of 20 to 200, imageability rating greater than 100, age of acquisition less than 7 years and Kucera-Francis written
frequency greater than 80 (Wilson, M., 1988. The MRC Psycholinguistic Database: Machine Readable Dictionary, Version 2. Behav. Res. Methods Instrum. Comput. 20, 6–11.). The duration of the words ranged from 0.5 to 0.7 seconds. The total length of each video clip
ranged from 1.1 to 1.8 seconds in order to start and end each video with the speaker in a neutral, mouth-closed position and to include all mouth movements from mouth opening to closing.
 
Here is a link to a ZIP file containing all of the words. Please contact MSB if the link is broken.
https://dl.dropboxusercontent.com/u/70081110/MRC_Words_1_syl_words.zip
 
==Unisensory Stimuli==
===Auditory stimuli===
The stimuli were presented with a grey background on the monitor. If you would like to use any of the following stimuli please cite as: Basu Mallick, D., Magnotti, J.F. & Beauchamp, M.S. (2013). Wide variability in McGurk perception across stimuli. Manuscript in preparation.
==== Male Speaker====
* [http://openwetware.org/wiki/Image:John_ba_aonly.wav /ba/]
* [http://openwetware.org/wiki/Image:John_pa_aonly.wav /pa/]
* [http://openwetware.org/wiki/Image:John_baba_aonly.wav /baba/]
* [http://openwetware.org/wiki/Image:John_papa_aonly.wav /papa/]
 
==== Female Speaker====
* [http://openwetware.org/wiki/Image:Sarah_ba_aonly.wav /ba/]
* [http://openwetware.org/wiki/Image:Sarah_pa_aonly.wav /pa/]
* [http://openwetware.org/wiki/Image:Sarah_baba_aonly.wav /baba/]
* [http://openwetware.org/wiki/Image:Sarah_papa_aonly.wav /papa/]

Revision as of 11:43, 5 September 2014

Brain picture
Beauchamp Lab




Notes on the McGurk Stimuli

The McGurk-MacDonald effect is an audiovisual illusion. Here are some audiovisual files that can be used to demonstrate the effect. McGurk stimuli consist of an auditory syllable and an incongruent visual syllable that produce the percept of a different syllable (e.g. auditory "ba" + visual "ga" perceived as "da"). Other incongruent stimuli (e.g. auditory "ga" + visual "ba") do not produce the effect. Here is an archive of some the stimuli used in our publications, referenced in Beauchamp:Publications. McGurk and Other Stimuli Archive

Note that some of these files require a particular video codec that is freely available in the VLC player, available from http://www.videolan.org/vlc/

To see the stimuli on any platform, you may view them on YouTube

  1. Auditory "ba" + Visual "ga" --> AV "da" http://www.youtube.com/watch?v=WK3T7LWIkP8
  2. Auditory "pa" + Visual "ka" --> AV "ta" http://www.youtube.com/watch?v=An5vvn-gcwA

See also Beauchamp:Stimuli for other McGurk YouTube examples.

Single-syllable audiovisual words

Please cite

  1. Nath, AR and Beauchamp, MS. A Neural Basis for Interindividual Differences in the McGurk Effect, a Multisensory Speech Illusion. Neuroimage. 2012 59:781-787.
  2. Nath, AR, Fava EE and Beauchamp, MS. Neural Correlates of Interindividual Differences in Children's Audiovisual Speech Perception. Journal of Neuroscience. 2011 Sept 28;31(39)13963-13971.

The following is from the methods section of Nath and Beauchamp (2012):

Word stimuli for the localizer were selected from two hundred single-syllable words from the MRC Psycholinguistic Database with Brown verbal frequency of 20 to 200, imageability rating greater than 100, age of acquisition less than 7 years and Kucera-Francis written frequency greater than 80 (Wilson, M., 1988. The MRC Psycholinguistic Database: Machine Readable Dictionary, Version 2. Behav. Res. Methods Instrum. Comput. 20, 6–11.). The duration of the words ranged from 0.5 to 0.7 seconds. The total length of each video clip ranged from 1.1 to 1.8 seconds in order to start and end each video with the speaker in a neutral, mouth-closed position and to include all mouth movements from mouth opening to closing.

Here is a link to a ZIP file containing all of the words. Please contact MSB if the link is broken. https://dl.dropboxusercontent.com/u/70081110/MRC_Words_1_syl_words.zip

Unisensory Stimuli

Auditory stimuli

The stimuli were presented with a grey background on the monitor. If you would like to use any of the following stimuli please cite as: Basu Mallick, D., Magnotti, J.F. & Beauchamp, M.S. (2013). Wide variability in McGurk perception across stimuli. Manuscript in preparation.

Male Speaker

Female Speaker

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