Differential effect of directed attention on input versus output pathways
The effect of directed attention cued by a peripheral cue or foveal stimulus on a temporal discrimination task and simple RT detection task was investigated. Directed attention (both voluntary and automatic) demonstrated no effect on peripheral temporal discrimination. The simple RT detection task was employed to investigate the spatial aspects of directed attention as well as the efficiency of various cue-types. The no-cue condition was superior to both a peripheral and a foveal or central cue condition. It was concluded that spatial cues incur costs rather than benefits to RT and these costs are directly related to the SOA interval between the cue and target. The comparison of spatial cues showed peripheral cueing to be superior to central cueing. This finding was attributed to longer cue processing time and attention shift time required by the central cue. For both spatial cues, clear advantages were found for the cued hemifield relative to the miscued (opposite) hemifield. Within hemifield differences between cued and miscued targets were not found. These results indicate that in this study directed attention operated like a "floodlight" restricted to the attended hemifield rather than as a "flashlight" or beam. Kinsbourne's attentional model of cerebral lateral asymmetry appears to be consistent with this floodlight mechanism. Attentional biasing of the cued hemisphere however did not facilitate motor (output) channels. Additional evidence was presented to suggest the possibility that under the condition of voluntary attention, some intrahemifield differences between cued and miscued targets may occur. Independent findings as well as physiological evidence to support this possibility that attention may additionally operate like a spatially restricted "flashlight" or "beam" were also discussed.