Constant and variable aspects of the dichotic listening right-ear advantage: A comparison of standard and signal detection tasks

Abstract

The study was designed to disentangle perceptual and attentional components of the dichotic listening right-ear advantage (REA). A total of 120 normal adults (108 right-handers and 12 left-handers) were administered the Halwes Fused Dichotic Words Test (FDWT) under standard conditions, which entail a forced-choice response format and no attention instructions. Two weeks later, the same stimuli were administered in a signal detection format with varied attention instructions (left, right, and equally divided). The standard task yielded the expected REA. The signal detection task yielded an REA for detection of targets that remained invariant across attention conditions. In contrast, ear asymmetry for localisation of targets varied with attention instructions. The REA on the standard task was correlated with the asymmetry of target detection (r = .57) on the signal detection task but not with the asymmetry of localisation or response bias. Ear asymmetry on the standard test seems to reflect an early stage of processing that is not altered by shifts of attention. Volitional shifts of attention influence the localisation of targets, but this component of signal processing is unrelated to the REA obtained on the standard test.