Memory overload or expectancy effect? ‘Hysteresis’ revisited*

Abstract

The effects of expectancy and variation in task demand on the rate of human information transmission were studied. Subjects performed an eight-choice key-pressing task, attempting to match characters presented singly under both increasing and decreasing demand. The results support previous research indicating that the relationship between the rate of information an individual is able to transmit and task demand depends, at least in part, upon the temporal history of demand. When a relatively high level of demand was imposed, performance failed to recover at the expected rate as demand was reduced. However, this ‘hysteresis’ effect occurred even when a cue was provided to indicate clearly that a reduction in task demand was imminent, suggesting that an overload of short-term memory, rather than an individual's erroneous expectations regarding demand, is primarily responsible for the effect.