Differences in pitch between tones affect behaviour even when incorrectly identified in direction

The ability to detect differences between simultaneously presented contra- and ipsilesional stimuli but not to identify the former on neurological patients with the symptom termed 'extinction' has given rise to the hypothesis that extinguished stimuli have impaired access to attentive processing but are detected pre-attentively. Such a dissociation found in normal participants with experimentally degraded sensory information, and its absence in equivalent tasks in terms of the amount of information required has, however, led to an alternative hypothesis that the lesser amount of information required to perform same/different judgements is sufficient to explain this dissociation. In the present paper, the correctness and reaction time (RT) of normal participants' forced-choice decisions about whether the second (comparison) tone of a pair of tones is higher/lower in pitch than the first (standard) tone were measured. It was found that even when participants' decisions were incorrect, the RT of these decisions varied as a function of the magnitude of the difference in pitch between the two tones. The first hypothesis was supported in the sense that stimulus differences might affect behaviour even without their successful attentive processing in normal participants.