Set size and order requirements in immediate memory

JAMES V. HINRICHS 0 GAIL McKOONt 0 0 University of Iowa , Iowa City, Iowa 52240 1 This research was supported by Grant MH-16362 from the National Institute of Mental Health. The second author was a member of the Undergraduate Research Participation program supported by National Science Foundation Grant GY6113 2 Now at the University of Colorado. Boulder , Colorado 80302 Three types of order requirements in the immediate recall of number sequences were investigated in two experiments. Experiment I examined written recall and Experiment II spoken recall. Natural serial recall was found to be superior to same order and free recall (a) in Experiment I because repeated correct intrusions were reduced, and (b) in Experiment II because more responses were produced. Implications for the analysis of mnemonic devices were briefly introduced. - At least three different recall order requirements can be distinguished in immediate memory experiments employing short sequences of homogeneous material: same order recall, natural serial recall, and free recall. Requiring same order recall is clearly the most stringent of the three: 5 is required to remember the items in exactly the same order as they were presented. In free recall, no recall order is imposed upon S; he is free to recall the items in any order he wishes. However, the use of free recall procedure does not eliminate a recall order requirement. Even though no specific order is specified, S still must recall the items in some order; the order, however, is self-imposed rather than experimenter-imposed, The natural serial recall order would appear to be immediate between same order and free recall requirements. In the natural serial recall method, Ss are required to produce the items in their natural ascending sequential order, such as numbers in cardinal order or letters in alphabetical order. Therefore, an order requirement is imposed upon S, but the order is well known and overlearned. Comparison of natural serial recall with free recall and same order recall raises some questions about expected degree of difficulty. On the one hand, natural serial recall might be expected to be superior to same order recall but inferior to free recall because retention of order information is required but the particular order is very well learned and known to Ss in advance. On the other hand, natural serial recall might be expected to be superior to free recall because it provides an efficient organization upon which to base later retention. In fact, Buschke and Hinrichs (1968) found little difference between natural serial and free recalL although both were superior to either forward or backward recall orders. Their study was restricted to 1Odtern sequences, and performance was very high in both natural serial and free recall conditions. Therefore, one purpose of the present series of experiments was to explore natural serial and free recall over several set sizes and restrictions in production order to distinguish any possible differences in retention. Hinrichs and McKoon (1971) demonstrated that order and number requirements play an important role in distinguishing between natural serial and same order retention. Depending upon the number of responses required, the order of production of the responses and the modality of the responses may both influence the retention of order information. For example, when Ss are allowed to use spoken recall, the free recall procedure would appear to have an important advantage. With spoken recall, Ss may produce the responses in any order they please in the free recall condition. However, in natural serial and same order recall, the items must be produced in a particular final order. In other words, with spoken recall, production order and final protocol order must be identical. However, with written recall, production order and the final recall order need not be identical. Unless otherwise restricted, Ss have the option of producing their responses in any order they choose. Therefore, another goal of the present.research was to consider the role of restrictions in production order for retention of order information. Consequently, both written and oral recall methods were investigated in separate experiments. Subjects and Design The Ss were 54 members of introductory psychology classes at the University of Iowa who fulfilled a course requirement by participating in the experiment. All Ss were tested in groups of two or three individuals and were screened from each other's view during the experiment. The Sswere assigned to one of three recall groups, 18 Ss per group, according to a prearranged assignment schedule. The recall groups differed according to the required order of recall: same order - the same order as the items were presented: natural serial-the items were required to be ~c'"-~= arranged into their numerical ascending order: and free recall-no response order was specified. Within each recall group, three sequence lengths were presented. Ten sequences of 10. 15. and 25 numbers were presented in three blocks with order of administration of the blocks counterbalanced across Ss. Each presented sequence consisted of a series of two-digit numbers chosen from a set size exactly twice the length of the presented sequence. The 10-item sequences consisted of 10 numbers from the set of 20 numbers from 21 to 40 inclusive; the 15-item sequences consisted of 15 numbers from the 30-member set from 21 to 50; and the 25-item sequence consisted of 25 numbers from the 50-item set from 21 to 70. The numbers in each sequence were chosen randomly from the designated set WIth the constraint that no number could appear more than once within each sequence. The same set of 30 sequences was used for all Ss. The numbers were presented aurally via a tape recorder at a l-item/sec rate with the beginning and the end of each sequence signaled by a tone. After the tone at the end of the sequence, Ss recalled the numbers by writing them in boxes on answer sheets with the number of boxes provided for each sequence equal to the number of items in the presented sequence. In the same order condition. Ss were required to list the first number presented in the first box, the second in the second box, and so forth. In the free recall condition, Ss could place any number in any box. In the natural serial condition. Ss were instructed to list the smallest presented number in the first box. the second smallest number in the second box, and so forth. In all recall conditions, Ss were required to list as many numbers as were presented. guessing whenever necessary. The order of production of the responses was not specified so that Ss were permitted to begin listing responses in any response box and could skip from any box to any other box. Although the Ss were strongly instructed not to deviate from the required recall order, responses out of order were accepted in order to equate response opportunity among the three conditions. (...truncated)