Manipulating the spatial arrangement of stimuli in a precuing task.

Within the context of the spatial precuing paradigm a consistent finding is that, with hands placed adjacently, precuing of two fingers on the same hand results in faster discrete finger responses than precuing of two fingers on different hands. This phenomenon is known as the 'hand advantage'. The present study examined the possibility that perceptual factors contribute to this hand advantage. Results showed that the perceptual manipulation of moving the two center stimulus positions each one position inwards significantly reduced the hand advantage over the first 250 ms of preparation interval. This result was interpreted as reflecting a perceptual locus of the hand advantage. Perceptual encoding processes were tentatively postulated to operate according to the familiar subgroup hypothesis, which claims that spatial precues may differ in the 'familiarity' or 'strength' of the subgroups they create. The fact that a significant hand advantage remained present was taken as evidence in support of post-perceptual processes mediating the hand advantage. On the basis of these findings we argue that both perceptual and post-perceptual processes play a role in the spatial precuing task and mediate the hand advantage.