3.5 Auditory Perception

As is the case with visual perception, our auditory perception of the world relies on much more than the vibrating air entering our ear canals. It can vary based expectations related to context and familiarity, again revealing our reliance on top-down perceptual processes. We will return to this in the Language chapter in more detail but I offer a few examples here.

An interesting auditory illusion that highlights our tendency to organize or group sounds based on experience was put together by Diana Deutsch and colleagues (Deutsch, 1975). In this illusion, musical notes are played across stereo presentation such that when played together, it sounds ascending and descending scales are being played simultaneously, one in each ear. However, if you isolate each channel, you find that in each individual channel, the notes are actually jumping around. An example of this illusion is below and works best if you use headphones:

Note that with headphones, if both sides are playing at the same time, our brain tends to organize the sounds so it appears that one scale is played in one ear and the other scale is played in the other ear.

Another interesting auditory illusion identified by Diana Deutsch is referred to as the “Speech- to-song” illusion (Deutsch, 2019). Deutsch famously (in some circles anyway) stumbled across this illusion when recording spoken content for a CD and looped a passage during the editing process. She came back to it later believing that she was hearing singing, but it was the same passage again on repeat. In this case, we find that our perception of speech can change depending on context, and in this case, looping the speech repeatedly is enough to shift that context by providing a sense of rhythm and repetition. While there are speech events we consider categorically different from normal speech (e.g., rap or poetry), this illusion demonstrates how the same stimulus can shift from being perceived as one type of event to another. A video demonstration can be found below, and a more detailed explanation can be found at Deutsch’s website here. Note that if you go back and listen to the original sentence, for many listeners, it seems as though it starts off as speech, breaks into song, and then goes back into speech again.