Personality and dual-task processing: Disruption of procedural learning by declarative processing

In two experiments, procedural learning, consisting of serial reactions to predictable/random target movements, was studied (1) under either (a) dual-task or (b) single-task conditions for blocks 1–3, and then under (2) single-task conditions for blocks 4–6. In Experiment 1, the declarative dual-task comprised mental arithmetic; in Experiment 2a, the counting of nonsense syllables. Mental arithmetic, but not the less cognitively demanding counting of nonsense syllables, significantly impaired procedural learning (a further control condition during dual-task processing, comprising all random targets, eliminated the possibility that latent learning occurred under mental arithmetic). Personality factors, viz. Psychoticism and Neuroticism (Experiment 1), and Psychoticism (Experiment 2a), modified the effects of dual-task processing, although these effects were modest in terms of effect size. High scores on Psychoticism were associated with an erratic pattern of performance during single-task processing in blocks 4–6, pointing to a perseveration of the effects of dual-task processing in blocks 1–3. A further experiment (2b) showed that there was little awareness of the procedural rule used in Experiments 1 and 2a. Results point to the general conclusion that there are considerable individual differences (related to Psychoticism and Neuroticism) in the effects of dual-task processing on procedural learning, sufficient to either obscure or confuse the effects of experimental variables. In order to illustrate the possible implications of these experimental and personality results, the behavioral phenomenon of latent inhibition is discussed.