Serial position and clustering effects in a chimpanzee's "free recall".

Abstract

Lana, a chimpanzee sophisticated in the language Yerkish, was tested for free recall on lists consisting of from one to eight words randomly drawn from one of three taxonomic categories or on lists consisting of nine words with every third word from a different category. Serial position effects were observed for the four- to eight-item lists, with statistically significant first-item primacy effects on the seven- and eight-word lists and last~position recency effects on the six-, seven-, and eight-word lists. Also, above-chance clustering was observed in the recall of the nine-item categorized lists. These results were compared and contrasted with the serial position and clustering effects obtained in free recall with humans. Several alternative theoretical accounts of the results were considered.