Nancy C. Waugh

Short-term memory and intertrial interval

Subjects attempted to recall a single word-triad after 9-sec retention interval. The interval between successive tests (each with a different triad) was varied over a wide range. Proactive inhibition was found to decrease as a function of the length of the intertrial interval; when this interval exceeded 2 min, proactive inhibition was negligible. It did not appear to cumulate across a series of several trials.

Age-related differences in naming latency.

Older people seem to have difficulty learning new materials, perhaps because it takes them longer to retrieve relevant encoding information from memory. To assess the effects of age on speed of retrieval, 60 healthy males from 25 to 74 were shown pictures of common objects they were to name aloud as quickly as possible. The older subjects took longer to name the pictured objects. This difference was minimized with practice or when the name was cued, but did not interact with word frequency. The pattern of results for healthy older subjects was not similar to that found by Wingfield for brain-damaged subjects.

On the effective duration of a repeated word

Three experiments on immediate free recall are reported. Lists of words were read rapidly or slowly or at a variable rate; some items occurred only once while others were presented two or more times within a list, either in immediate succession or at widely separated locations. The results indicate that an items frequency of recall depends not only on how often it is presented, and for how long, but also on the average duration of the items that surround it. When the rates at which items occur exceed the rate at which they can be processed for storage, S evidently attends fully to each in turn; while in the opposite case he evidently tries to distribute his attention as evenly as possible among all of them.

Free recall of conspicuous items

Subjects attempted to recall lists of homogeneous unrelated words, some of which had been accompanied by a signal denoting that they were to be specially attended to. The results are consistent with the idea that “isolated” items are well retained because they are held in mind for a relatively long time.

A stochastic model for free recall

A statistical model for verbal learning is presented and tested against experimental data. The model describes a Markov process with a realizable absorbing state, allowing complete learning on some finite trial as well as imperfect retention prior to this trial.

The measure of interference in primary memory

The S s attempted to remember a minimally rehearsed serial association after attending to a sequence in which items were either ordered at random or repeated according to certain rules. The results indicate that, although a new and unpredictable item may displace an earlier one from primary memory, a recently presented and redundant one does not.

The effect of intralist repetition on free recall

Summary The S s were presented with lists of unrelated English words which they were to recall in any order. Within each list, four different words were repeated two, three, four, and five times, respectively. The proportion of repeated words that were recalled consistently exceeded the proportion predicted by the all-or-none hypothesis, which states that items are memorized either completely or not at all.

Proactive inhibition of prompted items

Retention of three-item lists was measured after 15 sec of interpolated activity. Recall was either prompted by the first word of a list or it was not: lists were presented after a very short or after a relatively long intertrial interval. Data from Ss differing widely in age and educational background failed to support the hypothesis that prompted recall should result in less proactive inhibition than unprompted; proactive inhibition in short-term memory may accordingly represent a deficit in storage rather than retrieval.

Age-Related Differences in Mental Performance

The effects of age and socioeconomic status on two sets of measures of cognitive performance were reviewed. One set consisted of the 12 subtests of the General Aptitude Test Battery; the other was a group of laboratory-based experiments, most of which were initiated by the late George A. Talland. The relationships among the various measures of performance within and between the two sets were examined. Finally, plans for future studies of age-related differences in cognitive performance were outlined. The four principal findings are as follows. (1) Age-related declines in performance were found in all subtests of the General Aptitude Battery. Performance declined least in those subtests where the effects of socioeconomic status were strongest and most in those subtests where socioeconomic status effects were weakest. There was no evidence for a significant interaction between the effects of differences in age and socioeconomic status. (2) It is more difficult for older individuals than for younger ones to (a) retrieve special information from short-term memory, (b) monitor two verbal sequences concurrently, and (c) initiate a response in a two-choice discrimination. Variations in performance on those tasks were not systematically related to socioeconomic status or education. (3) In both sets of measures, the major age-related differences in the level of performance were observed between subjects in their sixties or seventies and the younger ones. The largest age-related decrements occurred in tasks which were probably relatively unfamiliar in content or in form to the subject. (4) There was little overlap among the assessments of abilities represented by the General Aptitude Test Battery and the various Talland experiments.

Encoding Deficits in Aging

The ability to register, retain, and recollect experienced events is basic to every other higher mental process. Remembering is an essential component of problem-solving, concept-formation, and intelligent decision-making. By now there exists a growing mass of evidence that memory undergoes progressive deterioration throughout the late adult years, even in the absence of specific neurological disease. It takes the normal elderly individual longer than it does the young adult to assimilate, search for, and locate information, both verbal and nonverbal— and he is less likely to do so successfully. Different processes may, as Walsh has indicated (Chapter 6), decline at different rates within the same individual, and I the pattern is not necessarily the same from subject to subject. This is an important point to consider, all the more so if one wishes to construct and standardize more sophisticated tests of memory function than are currently available. We really ought to measure individual patterns of performance in the study of aging more than we do.