Saturday, 8 November 2008

Audiory Illusion

Every week I drive from my family home to stay at our cottage near the University. Normally I have the SatNav switched on - not because I don’t know the way (I’ve been doing this journey every week for the past four years), but because the SatNav beeps in advance of all the speed cameras along the route and I don’t want to earn a speeding ticket by an inadvertent lapse of concentration.

The other day I drove my regular route, but this time I didn’t have the SatNav (as it had been switched into my wife’s car). As usual I was listening to the radio, and on this particular night they were playing a live Oasis rock concert. As the journey progressed, I was amazed to find that on a number of occasions I was convinced that I could hear the usual speed camera warning beeps (issued by the non-existent SatNav)! As I became aware of what was happening, I noticed that I appeared to 'hear' the warnings at the exact times/locations on the road as they would have occurred if the SatNav had been on board.

The music was loud and cacophonous, so I can only assume that I experienced an auditory illusion that had been triggered by visual (episodic) memory – a dramatic illustration of the powerful top-down predictive nature of perception, and very much in line with my PRESENCE theory. Had I not had the radio switched on, then I’m sure that I would not have experience the illusion.


Kevin said...

It is an interesting experience.
Just do not understand why you said that:
"Had I not had the radio switched on, then I’m sure that I would not have experience the illusion."

At least to me, it seems more reasonable to have the audiory illusion if you didnot listen to music at that time. In other words, the audiory illusion may happen more frequently if the audio processing organ in your brain is NOT occupied by external sound such as music.

Stuart Cunningham said...

Hi Roger - Interesting post...

@Kevin: auditory illusions such as temporal induction and phonemic restoration only occur when acoustic energy is present sufficient to mask the illusory sound.

Perhaps, in this instance Roger expected to hear the warning sound and as the music *could* have masked it the illusory perception occurred.

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