Testing hearing in people who cannot respond by pressing a button, raising a hand, or speaking, such as infants, older children with developmental deficits, and adults who have a debilitating disorder or are too ill to respond is difficult.
But what if it was enough to examine the dilation of the pupils of the eyes?
Ocular dilation
Recently, two neuroscientists have published a study in the Journal of the Association for Research in Otolaryngology in which they use eye-tracking technology simultaneously while conducting traditional hearing exams with 31 adults .
Dilation was monitored for about three seconds while the participants looked at a point on a monitor while a tone was played.
The levels of dilation observed throughout the tests directly reflected the participants’ subsequent responses to whether or not a tone was heard .
In the tests, participants looked at a point on a screen, and listened to tones at 1, 2, 4 and 8 kilohertz, which were played in random delays to ensure that the subjects could not predict when the sound would appear.
The researchers observed that the pupils began to change within 250 milliseconds, about a quarter of a second, of the sound stimulus. The speed of response allowed the team to see and establish causality.
The neuroscientists authors of the singular study, Avinash Singh Bala and Terry Takahashi , are now collaborating with Dare Baldwin , professor of psychology, in the development of their own technology for testing babies.