Combining letter-matching and tone discrimination: Evidence of automatic perceptual and spatial congruity effects

Dual task and priming paradigms were combined to investigate the distinction between automatic and attentional processes. Subjects in two experiments performed a primed letter-matching and a tone discrimination task separately and concurrently. The interval between prime onset and letter pair (SOA) was varied from 50 to 500 msec. Cost-benefit analyses in Experiment 1 indicated that primes that matched target letter pairs began to facilitate performance at an SOA of 150 msec. Primes inhibited performance when they mismatched identical letter pairs at SOA 100. In the dual-task situation, the benefits of priming letter targets were reflected in probe latencies with no evidence of concurrent costs in tone latencies. Experiment 2 revealed that two tasks could be primed simultaneously as effectively as when each was primed alone. Findings are discussed in reference to Posner and Snyder's (1975a, 1975b) two-process theory of priming and the applicability of a secondary task technique.