A Test of Cue-overload Hypothesis on Formation of Proactive Inhibition

The purpose of this experiment was to investigate the cue-overload hypothesis on formation of proactive inhibition by manipulating both the kind of components in list and the number of items in list. Our hypothesis to examine was as follows: Proactive inhibition was formed slowly in the condition which the list consisted of small number of items and of two distinct categories. A 2×3×4 factorial design was used, which incorporated list components (dissimilar, similar and control), number of items (4 and 8 item) and trials (from 1 to 4). The subjects were 108 students at Nara University of Education with a mean age of 19 years and 2 months, who were assinged to one of the six conditions. Each list was consisted of four or eight words. Under the 4 (or 8)・dissimilar conditions, lists were consisted of 2 (or 4) words from each two categories which were dissimilar each other in semantic categories (e. g., vegetables and furnitures). Under the 4 (or 8)・similar conditions, lists were consisted of 2 (or 4) words from each two categories which were similar each other in semantic categories (e.g., vegetables and fruits). Under the 4 (or 8)・control conditions, lists were consisted of 4 (or 8) words from one category (e.g., vegetables, fruits or furnitures). The experiment was conducted individually by Brown-Peterson paradigm. Each item was presented through the television at a 1-sec rate. After 4 (or 8) items were presented all over, the distractor task (counting backwards by-three from a three digit number) was given during retention interval (18 sec) and then recall test was given for 15 sec (or 30 sec). Following the recall test, next trial was introduced until four trials were completed. The main results were as follows: Proactive inhibition was formed as a function of trials. The performances of 4 item conditions were higher than those of 8 item conditions in all trials. The differences of performance from trial 1 to 3 were larger than those of trial 4. Performance reductions on two adjacent trials were shown the different pattern of reduced performance. The performances of 4 item conditions decreased smaller than those of 8 item conditions from trial 1 to 2. By contrast, the performances of 8 item conditions decreased smaller than those of 4 item conditions from trial 2 to 3 and trial 3 to 4. These results were congruenced with our expectation based on the cue-overload hypothesis that degree of formation of proactive inhibition were become large as a function of the number of items in the list. The performances of correct recalled among the dissimilar, similar and control conditions were not different significantly each other. However the rate of reduced performances on two adjacent trials showed that on 4 item conditions the degree of reduced performance on the dissimilar conditions were smaller than those of similar and control conditions, and that on 8 item conditions the degree of reduced performance were not significantly different from each other condition. These results partially supported our expectations based on cue-overload hypothesis. From the above results on the number of item and composition of list, we suggested the possibility of some relatedness between cue-overload and memory-span