The relationship between central cues and peripheral cues in covert visual orientation.

Four experiments were conducted to compare valid and invalid cue conditions for peripheral and central cues. Experiments 1, 3, and 4 used reaction time (RT) as the dependent variable. Experiment 2 used a threshold measure. Peripheral and central cues were presented on each trial. The peripheral cue was uninformative in all experiments. The central cue was informative in Experiments 1 and 2, where it predicted stimulus side on 70% of the trials. Experiment 3 included 50% and 100% central-cue prediction conditions as well as the 70% treatment. Experiment 4 included 60%, 75%, and 90% central-cue prediction conditions. The effects of the central and peripheral cues were independent and additive in all four experiments, indicating that: (1) both cue types can act simultaneously, and that the relationship between them is additive under the conditions used in these experiments, (2) informativeness is not a necessary condition for attentional effects with peripheral cues, and (3) covert visual orientation influences sensory thresholds and RT in similar ways. The results of Experiments 3 and 4 demonstrated that the facilitation associated with peripheral cues was insensitive to manipulations which demonstrate that subjects use the informational value of the central cue to direct voluntary attention. The results are discussed with reference to two issues; first, the proposition that central and peripheral cues exert their influence on performance in independent information-processing stages, following the additive factor method, and, second, the problems raised for additive factors method when cues elicit both an "explicit" response-regarding the presence or absence of a specified letter-and an "implicit response"-involving the planning and possible execution of eye and hand movements.