General slowing of nonverbal information processing: evidence for a power law.

Data were analyzed from studies of nonverbal information processing in which the dependent measure was the latency of pressing or releasing a response key. Positively-accelerated power functions described the relationship between the response latencies of groups of older (50 to 60 years and 65 to 75 years) and younger adults (20 to 25 years) with extreme precision (r2 = .99). The exponent of the best-fitting power function increased with the age of the older group. The form of the relationship is allometric, and is consistent with a model (Botwinick, 1984) in which response latency increases exponentially with task difficulty. The present findings suggest that this model holds across a wide variety of information-processing tasks and over a very broad range of latencies.