Kenneth R. Laughery

Computer Simulation of Short-Term Memory: A Component-Decay Model

Publisher Summary This chapter discusses the computer simulation of short-term memory. The first of these systems is the sensory storage or very-short-term memory, viewed as a peripheral or perceptual storage. There is general agreement that information stored in this type of memory decays with time and is lost in a matter of a few seconds or less. Another type of memory, short-term memory (STM), is the focus of these various models. Despite general agreement that information is lost from STM, there are two views as to the nature of this loss. One view is that information is lost as a result of decay; an alternative is that STM has a limited capacity so that items are lost by being replaced by new items entering the system. The model represents the human at an information-processing level of description. At this level, the human is viewed as having available a variety of processing mechanisms which can be employed to operate upon information.

Detection of vehicle velocity changes during expressway driving

The time required by an observer in a moving vehicle to detect controlled accelerations and decelerations by the vehicle ahead was measured for automobiles travelling on a four-lane, divided, limited-access highway. Two levels of rate of velocity change and two initial intervehicle separations were studied. Detection time increased with intervehicle separation and decreased with increasing rate of change.

KEEPING TRACK OF SEQUENTIAL EVENTS: EFFECTS OF STIMULUS ON-TIME AND INTERSTIMULUS OFF-TIME

Ss were required to keep track of the number of occurrences of each of four different letters (categories) presented sequentially as a function of the total number of letters presented (trial length), the rate of presentation, and the two components which, when combined, constitute the rate, namely, stimulus on-time and the interstimulus interval or off-time. In general, performance varied inversely with trial length and rate of presentation. Of greater importance, however, was the complex interaction between the rate of presentation and the components of that rate. At the fastest rate, performance was relatively invariant as a function of these components; at intermediate rates the shortest on-time led to the best performance, while at the slowest rate the shortest on-time led to the poorest performance. The observed results are explained primarily in terms of the time available for rehearsal.

Short-Term Memory: Mode of Presentation for Alphanumeric Information1

Performance in a memory-span task using eight-letter sequences was explored as a function of presentation rate (.5, .75, 1.0, 2.0, and 3.0 sec/item) and presentation mode (visual, auditory, simultaneous visual and auditory, and mixed visual and auditory). Results indicate that performance in the mixed mode was inferior to the other three modes, but the other modes did not differ from each other. As presentation rate decreased, performance improved. These results are consistent with current theories of memory and indicate that the mode in which alphanumeric information is displayed is unimportant provided the modes are not mixed.

The effect of rate of presentation, substitution, and mode of response in paired-associate learning.

The meaning of the phrase to form an association serves as a focus for the expe-riments to be reported here. Inferences about the processes that enable S to learn paired-associates range from analogies to the classical conditioning paradigm to assumptions of highly cognitive mediating acts.l In the conditioning analogy, there are, presumably, incremental increases in stimulus-response strength over successive repetitions of the pairs. Our own biases tend toward the view that most performance changes in the human adult depend on cognitive processes utilizing information previously acquired. The data presented by Rock were therefore of particular interest to us.2 It was Rocks contention that an association between the elements of a pair is formed in a single trial. Repetition is not necessary for the formation of associations, but does assume importance in that only a few associations may be formed on any one trial. Hence, to learn a long list of items, the list must be repeated. Two experiments were carried out using the general procedure employed by Rock. In Experiment I, the Ss were required to spell the nonsensesyllables, instead of pronouncing them, at two different rates of presentation. In Experiment II, a direct comparison of the spell vs. pronounce modes of response was made at a single rate of presentation identical to that used by Rock. The purpose of these procedural changes was to determine the generality of the phenomenon reported by Rock. Specifically, it was hypothesized that in a more diScult task Rocks conclusions will not be supported.

A simulation model of short-term memory: Parameter sensitivity studies and implications for two current issues ☆

Abstract A simulation model of human short-term memory (STM) has been formulated. The model postulates a number of basic information processes which are executed in a serial fashion and each has an associated time parameter. The model also postulates that information is lost from memory as a result of decay. The nature of this decay is exponential and its rate is a model parameter. Several studies were simulated in which the processing-time and decay-rate parameters were manipulated to determine the models sensitivity to these parameters. Also, the models performance was examined as a function of whether or not visual information is stored in STM and whether order information is retained perfectly or lost as a result of decay. The results of these simulated studies were compared to experimental data to determine at which parameter values and under which conditions of visual and order information storage the model performs most appropriately.