Item-to-Item Associations Contribute to Memory for Serial Order

Abstract

Since Ebbinghaus’ (1885) work more than a century ago, there has been substantial interest in understanding how people store and retrieve information in order. The field has largely relied on the serial recall procedure to examine how serial order is accomplished in memory. The research using this procedure has emphasized that associations are formed between items in the sequence and their serial positions (position-to-item associations) and that a sequence is reproduced by stepping through the positions and retrieving the item most strongly associated with each. It is generally assumed that the associations that form between items (item-to-item associations) are not used to remember a sequence. I present a series of experiments that test this assumption, using a serial learning procedure inspired by Ebenholtz (1963). In this procedure, participants practiced recalling ordered lists of letters, and the order of the letters was manipulated. Half of the lists were scrambled such that the serial positions and relative positions of the letters were inconsistent over practice. The other half of the lists were instead spun, making the serial positions inconsistent but preserving the relative positions of the letters over practice. When the relative positions are consistent, the item-to-item associations between letters are given the opportunity to strengthen. If the generally held assumption about item-to-item associations is correct, then the consistency in relative positioning should not matter – the rate of learning spun and scrambled lists should not differ. If the assumption is incorrect, learning should be faster for the spun lists. The results of my experiments indicate that the commonly held assumption is incorrect; spun lists were learned more quickly, so item-to-item associations were used to remember a sequence. Memory for serial order is more complex than contemporary theories describe; both position-to-item associations and item-to-item associations contribute to retrieval. The information used to remember ordered lists is also used to remember unordered lists (i.e., free recall), so the memory system does not seem to have a specialized solution for the problem of serial order.