Hearing a sound can alter perception of finger size

Hearing an ascending sound while pulling their own finger can make a person think their finger is longer than it is, finds a new study led by UCL and the Institute of Philosophy, School of Advanced Study, University of London. The study, published in Scientific Reports and funded by the Economic and Social Research Council (ESRC) and the Arts and Humanities Research Council (AHRC), provides the first evidence that an artificial sound, unrelated to the sound of body movements, can alter how a person perceives their own body when the sound is arbitrarily paired with a bodily action. 'Just like how cartoons will play a rising-pitch sound effect to illustrate something being stretched, we found that playing a rising pitch while people pull on their finger can give people the impression that their finger is longer,' said the study's lead author, Dr Ana Tajadura-Jiménez (UCL Interaction Centre and Universidad Loyola Andalucía). In a series of three studies, female participants were asked to pull on their index finger while a simple sound was played, with ascending, descending, or constant pitch. Their hand was hidden from view by a black cloak. They were then asked to estimate the position of their fingertip and of their knuckle by using a pair of sliders. The distance between the two sliders represented how long they judged their finger to be, without being able to see it.