The study by Nakayama and MacKeben investigates the components of focal visual attention, specifically sustained and transient components. In a series of experiments, human observers were asked to discriminate an odd target in a search array, which could be either simple (defined by orientation) or conjunctive (defined by both orientation and color). The array was presented for a variable duration, and a cue was either visible all the time (sustained cuing) or appeared transiently before the array (transient cuing). The results showed that sustained cuing significantly enhanced performance in the conjunctive condition but not in the simple condition. Transient cuing further improved performance, with peak discrimination occurring when the cue preceded the target array by 70-150 msec. Longer delays led to a significant decline in performance. Control experiments indicated that the transient attentional component was independent of prior knowledge and not subject to voluntary control. The authors suggest that the transient component does not originate at the earliest stages of visual processing, as it could not be extended by flickering the cue and did not require a local sensory transient to trigger its onset. The findings indicate the existence of two distinct attentional processes: a sustained and a transient component, with the transient component operating at an earlier stage of visual cortical processing.The study by Nakayama and MacKeben investigates the components of focal visual attention, specifically sustained and transient components. In a series of experiments, human observers were asked to discriminate an odd target in a search array, which could be either simple (defined by orientation) or conjunctive (defined by both orientation and color). The array was presented for a variable duration, and a cue was either visible all the time (sustained cuing) or appeared transiently before the array (transient cuing). The results showed that sustained cuing significantly enhanced performance in the conjunctive condition but not in the simple condition. Transient cuing further improved performance, with peak discrimination occurring when the cue preceded the target array by 70-150 msec. Longer delays led to a significant decline in performance. Control experiments indicated that the transient attentional component was independent of prior knowledge and not subject to voluntary control. The authors suggest that the transient component does not originate at the earliest stages of visual processing, as it could not be extended by flickering the cue and did not require a local sensory transient to trigger its onset. The findings indicate the existence of two distinct attentional processes: a sustained and a transient component, with the transient component operating at an earlier stage of visual cortical processing.