Individual Differences in Behavioral Decision Weights Related to Irregularities in Cochlear Mechanics

Jungmee Lee, Inseok Heo, An-Chieh Chang, Kristen Bond, Christophe Stoelinga, Robert Lutfi, Glenis R. Long

An unexpected finding of previous psychophysical studies is that listeners show highly replicable, individualistic patterns of decision weights on frequencies affecting their performance in spectral discrimination tasks – what has been referred to as individual listening styles (Doherty and Lutfi, 1996; Lutfi and Liu, 2007; Jesteadt et al., 2014). We, like many other researchers, have attributed these listening styles to peculiarities in how listeners attend to sounds, but we now believe they partially reflect irregularities in cochlear micromechanics affecting what listeners hear. The most striking evidence for cochlear irregularities is the presence of low-level spontaneous otoacoustic emissions (SOAEs) measured in the ear canal and the systematic variation in stimulus frequency otoacoustic emissions (SFOAEs), both of which result from back-propagation of waves in the cochlea. SOAEs and SFOAEs vary greatly across individual ears and have been shown to affect behavioural thresholds, behavioural frequency selectivity and judged loudness for tones (Long and Tubis, 1988, Baiduc, Lee and Dhar, 2012, Mauermann, Long and Kollmeier, 2004). The present paper reports pilot data providing evidence that SOAEs and SFOAEs are also predictive of the relative decision weight listeners give to a pair of tones in a level discrimination task. In one condition the frequency of one tone was selected to be near that of an SOAE and the frequency of the other was selected to be in a frequency region for which there was no detectable SOAE. In a second condition the frequency of one tone was selected to correspond to an SFOAE maxima, the frequency of the other tone, an SFOAE minima. In both conditions a statistically significant correlation was found between the average relative decision weight on the two tones and the difference in OAE level.