The course of proactive interference in immediate probed recall

Measurement of RT in positionally probed immediate recall was used to study the effect of interlist proactive interference (PI) on short-term retention in near- and subspan lists. The first experiment showed a pronounced effect of PI in the sense of a constant increase of RT, but only to the first three serial positions. This was confirmed in a second study that further showed that the size of PI was independent of the size of the preceding list. These results argue against a general acid-bath view of PI but are consistent with the hypothesis of degraded access to the first item. The minimal length of a list susceptible to PI was five items which suggests that PI develops as soon as the list grows beyond the span of direct access to all individual items.