Item difficulty and distribution of practice in short-term memory

The effects of the difficulty of the material to be remembered, memory ability of the subjects and the distribution of practice on short-term memory, were investigated.;Recall of stimuli of all difficulty levels, and for subjects of all memory ability levels, was found to improve as the time between the two presentations increased. Subjects of all memory ability levels improved at the same rate, and the rate of improvement was greatest for the least difficult stimulus items.;The findings were discussed in terms of Walker's action decrement theory.;Stimulus items were six-letter, sequences of three different levels of approximation to English. These were presented visually and subjects were required to spell them aloud. Subjects were tested for recall at various intervals after single presentations of the stimuli and divided into three groups according to their memory ability. To minimize rehearsal, the interval between presentation and recall was filled by reading out numbers aloud. In trials with practice, the stimuli were presented twice each with interpresentation intervals varying from 0 to 30 seconds. Recall was tested ten seconds after the second presentation. Interpresentation and retention Intervals were filled by reading out numbers.