Short-term retention of individual verbal items.

It is apparent that the acquisition of verbal habits depends on the effects of a given occasion being carried over into later repetitions of the situation. Nevertheless, textbooks separate acquisition and retention into distinct categories. The limitation of discussions of retention to long-term characteristics is necessary in large part by the scarcity of data on the course of retention over intervals of the order of magnitude of the time elapsing between successive repetitions in an acquisition study. The presence of a retentive function within the acquisition process was postulated by Hull (1940) in his use of the stimulus trace to explain serial phenomena. Again, Underwood (1949) has suggested that forgetting occurs during the acquisition process. But these theoretical considerations have not led to empirical investigation. Hull (1952) quantified the stimulus trace on data concerned with the CS-UCS interval in eyelid conditioning and it is not obvious that the construct so quantified can be readily transferred to verbal learning. One objection is