Attentional biases and the right-ear effect in dichotic listening

Most dichotic listening experiments permit subjects to deploy attention in any way they choose. We argue that this adds uncontrolled variance to the observed right-ear advantage. In the first experiment, more robust laterality effects were obtained in an identification task with focused than with divided attention. Such differences were not found in the second experiment, when a detection procedure was used. Virtually all the laterality effect observed in the second study could be attributed to subjects who were biased attenders, in the sense that they exhibited more intrusions from the right ear to the left than vice versa. However, rather than indicating that laterality effects are simply attentional bias, this effect can be attributed to an asymmetry of perceptual discrimination.