Attention, reliability, and validity of perceptual asymmetries in the fused dichotic words test

The present experiment investigated the claim that the fused dichotic words test (FDWT) is affected minimally by attentional factors. A total of 40 right-handed undergraduate students were randomly assigned to either a free recall or exogenous cueing condition. In the free recall condition, participants circled on a response sheet the word corresponding to the percept they heard for each trial. In the exogenous cueing condition, a lateralised tone cue was presented with a stimulus onset asynchrony (SOA) of either 150 or 450 ms. Participants responded by circling the word presented to the ear where the tone sounded. Results of the free recall condition showed the expected large right ear advantage (REA). In the exogenous cueing condition, the significant SOA by ear of presentation interaction predicted by an attentional explanation of perceptual asymmetries was obtained. Specifically, the REA obtained at the 150 ms SOA was reduced at the 450 ms SOA for both correct responses and intrusions. These findings suggest that, contrary to claims conveyed in the literature, the FDWT is subject to the influences of attention. This supports the claim that the large and reliable laterality effects obtained with the fused dichotic words test are due in part to a consistent attentional bias.