Effects of adult age on structural and operational capacities in working memory

Eight experiments were conducted in which young adults and older adults were asked to report the latest value of 1 of several continuously changing numeric or spatial variables. Accuracy of reporting the current value of the target variable was lower with increases in the number of potentially relevant variables and with increases in the number of required processing operations. Young and older adults exhibited similar effects of the number of potentially relevant variables (hypothesized to be sensitive to the structural capacity of working memory) and of the number of required processing operations (hypothesized to be sensitive to the operational capacity of working memory), but older adults were generally less accurate than young adults.     

Distignuishing the source of memories reported during prior waking and hypnotic recall attempts

Subjects attempted to identify the occasion on which they first reported particular responses to questions that were asked twice during an experiment on hyphosis and memory 1 week earlier. During this earlier experiment, subjects of high and low hypnotizability had been randomly allocatd to one of two recall test sequences: wake-hypnosis ro wake-wake. Recall improved from the first (R1) to the second test (R2) in a comparable manner for both test sequences, indicating a failure of hypnosis to enhance memory. It is noteworthy that, when later queried about the origins of specific recollections, the majority of subjects exhibited a bias to attribute their responses to R1, regardless of whether hypnosis was used during R2. Moreover, low hypnotizables exposed to the hypnotic procedure and, to a lesser extent, high hypnotizables who recalled both times in the waking condition displayed and exaggerated tendency to overattribute recollections to R1. These data indicate that individuals cannot distinguish between memories retrieved prior to hypnosis and those that occured during hypnosis. Implications for implementing judicial standards regarding hypnosis are discussed.     

Pilot personality and crew coordination: implications for training and selection

The performance of pilots can be construed as a product of skill, attitude, and personality factors. Although a great deal of effort within the aviation community has been focused on ensuring technical expertise, and new efforts highlight attitudes associated with crew coordination, personality factors have been relatively unexplored. Further, it is argued that past failures to find linkages between personality and performance were due to a combination of inadequate statistical modeling, premature performance evaluation, and/or the reliance on data gathered in contrived as opposed to realistic situations. The goal of the research presented in this article is to isolate subgroups of pilots along performance-related personality dimensions and to document limits on the impact of crew coordination training between the groups. Two samples of military pilots were surveyed in the context of training in crew coordination. Three different profiles were identified through cluster analysis of personality scales. These clusters replicated across samples and predicted attitude change following training in crew coordination.     

Second-order conditioning of the rabbit's nictitating membrane response. Interstimulus interval and frequency of CS-CS pairings.

Second-order conditioning of the rabbit's nictitating membrane response (NMR) was investigated when second-order trials (CS1-CS2) were intermixed with first-order trials (CS2-US) from the outset of training. Experiment 1 showed that CR acquisition to CS1 was inversely related to the CS1-CS2 interval but nevertheless extended to an interval of 8,400 ms. Experiment 2 revealed that CR acquisition of CS1 was an inverted-U function of the number of CS1-CS2 trials relative to a fixed number of CS2-US trials. Experiment 3 directly contrasted second-order conditioning with a reinforced serial compound procedure (CS1-CS2-US) and a mixed procedure in which second-order trials were intermixed with the reinforced serial compound. Second-order conditioning was about half the strength of either the reinforced serial compound or the mixed procedure, which were similar. The present results are discussed with respect to the relative strength of excitatory and inhibitory processes in second-order conditioning.     

Improving the retrieval of information from external sources

A major barrier to successful retrieval from external sources (e.g., electronic databases) is the tremendous variability in the words that people use to describe objects of interest. The fact that different authors use different words to describe essentially the same idea means that relevant objects will be missed; conversely, the fact that the same word can be used to refer to many different things means that irrelevant objects will be retrieved. We describe a statistical method called latent semantic indexing, which models the implicit higher order structure in the association of words and objects and improves retrieval performance by up to 30%. Additional large performance improvements of 40% and 67% can be achieved through the use of differential term weighting and iterative retrieval methods.     

Performance of humans in concurrent avoidance/positive-reinforcement schedules

Performance maintained under concurrent schedules consisting of a variable-interval avoidance component and a variable-interval positive-reinforcement component was studied in three human subjects using points exchangeable for money as the reinforcer. The rate of responding in the avoidance component increased, and the rate of responding in the positive-reinforcement component declined, as a function of the frequency of point-losses avoided in the avoidance component. The performance of all three subjects conformed to equations proposed by Herrnstein to describe behavior in concurrent schedules. The logarithms of the ratios of the response rates in the two components, and the logarithms of the ratios of the times spent in the two components, were linearly related to the logarithms of the ratios of the frequency of loss avoidance in the avoidance component to the frequency of reinforcement in the positive-reinforcement component. When a changeover delay of 5.0 sec was imposed, the slopes of the linear functions were close to 1.0 in the case of two subjects, whereas the third subject exhibited significant undermatching. For two subjects the changeover delay was then reduced to 2.0 sec; in both cases the slopes of the linear functions were lower than under the 5.0-sec condition. One subject participated in a third phase, in which no changeover delay was imposed; there was a further reduction in the slopes of the linear functions.