When something suddenly appears in our visual field, we
usually notice right away. That isn’t the case when something changes or
disappears. Even though the difference is equivalent, it takes us a lot longer
to register the loss or alteration of an object within our field of view. This
phenomenon has been termed ‘change blindness’. You can see an example here.
Apparently, the same is true for our sense of hearing.
University College London researchers led by Francisco Cervantes Constantino
tested people for ‘change deafness’. They played specific sets of 4 to 14 pure
tones for groups of people with normal hearing. Each auditory scene lasted from
two to four seconds. In some trials, a tone was either added or subtracted
partway through the sound-scape. You can see a visual representation of these
trials below.
No change: the scene was played unaltered.
Change-disappear: A single tone
was removed.
Change-appear: A single tone was
added.
Participants did significantly
better at detecting when a tone was added than when one was subtracted. As more
tones were added to the original mix, people became worse and worse at noticing
the disappearance of one sound. In contrast, the subjects were close to 100%
accurate in detecting the addition of a new tone even when listening to
fourteen other notes. People were also far more adept at identifying exactly which
tone had been added than which had been removed.
Francisco Cervantes Constantino, Leyla Pinggera, Supathum Paranamana, Makio Kashino, & Maria Chait (2012). Detection of Appearing and Disappearing Objects in Complex Acoustic Scenes PLoS ONE : doi:10.1371/journal.pone.0046167
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