Response probability and latency: a straight line, an operational definition of meaning and the structure of short term memory

The functional relationship between response probability and time is investigated in data from Rubin, Hinton and Wenzel (1999) and Anderson (1981). Recall/recognition probabilities and search times are linearly related through stimulus presentation lags from 6 seconds to 600 seconds in the former experiment and for repeated learning of words in the latter. The slope of the response time vs. probability function is related to the meaningfulness of the items used. The Rubin et al data suggest that only one memory structure is present or that all memory structures probed show the same linear relation of response probability and time. Both sets of data also suggest that the memory items, presumably in the neocortex, have a finite effective size that shrinks in a logarithmic fashion as the time since stimulus presentation increases or the overlearning decreases, away from the start of the search. According to the logarithmic decay, the size of the memory items decreases to a couple of neurons at about 1500 seconds for recall and 1100 seconds for recognition – this could be the time scale for a short term memory being converted to a long term memory. The incorrect recall time saturates in the Rubin et al data (it is not linear throughout the experiments), suggesting a limited size of the short term memory structure: the time to search through the structure for recall is 1.7 seconds. For recognition the corresponding time is about 0.4 seconds, to compare with the 0.243 seconds given by the data analysis of Cavanagh of Sternberg-like experiments (1972)

A QUANTITATIVE MODEL OF THE AMPLIFICATION OF POWER THROUGH ORDER AND THE CONCEPT OF GROUP DEFENSE

I propose a simple quantitative model of how the power of a leader over a group is amplified when he or she starts to order the group. This model implies that a small well-informed minority can easily govern a previously ordered majority such as hijacked passengers. The model leads to the concept, “group defense,” which stresses the importance of group members resisting enemy ordering and creating a counter-ordering. Group defense may be helpful in preventing fatal hijackings such as the ones that occurred on September 11 and other massacres on civilians

Initial Free Recall Data Characterized and Explained By Activation Theory of Short Term Memory

The initial recall distribution in a free recall experiment is shown to be predictably different from the overall free recall distribution including an offset which can cause the least remembered items to be almost completely absent from the first recall. Using the overall free recall distribution as input and a single parameter describing the probability of simultaneous reactivated items per number of items in the presented list, activation theory not only qualitatively but quantitatively describes the initial recall distributions of data by Murdock (1962) and Kahana et al (2002). That the initial free recall can be simply explained in terms of the overall recall suggests that theories of memory based on interference or other context sensitive information are false since knowledge of the future would have to be incorporated to predict the initial recall

The free recall search process introduces errors in short term memory but apparently not in long term memory

Here it is reported that the free recall search process increases the error rate for short term memory (about 1% per second in data from Murdock & Okada (1970)) but not for long term memory (in data from McDermott (1996)). If the short term memory search process introduces random excitations, which would account for the search errors, the subjects should be unaware of making such errors. This is in agreement with DRM findings (Gallo, 2010) and the new finding that the error terminated distributions in Murdock (1962) are the same as those terminated by studied items

The Atkinson-Shiffrin model is ill-defined and does not correctly describe the Murdock free recall data

The Atkinson-Shiffrin (1968) model, the de facto standard model of short term memory cited thousands of times, fits the characteristically bowed free recall curves from Murdock (1962) well. However, it is long overdue to note that it is not a theoretically convincing explanation and that it does not fit all of the experimental relationships in the Murdock data.\ud To obtain a qualitatively correct fit of the bowing I show that four model concepts have to work together. “Long term memory” is needed in the short term memory experiment, conscious or subconscious rehearsal of four items has to take place, this “rehearsal buffer” has to drop items randomly rather than according to a first-in firstout model, and the rehearsal buffer has to be empty before the experiment starts.\ud Beyond the qualitative fit to the bowed recall curves, other relationships in the data are not borne out by the model. First, the “primacy strength”, the ratio of the probability of recall of the first item to the smallest probability of recall of an intermediate item, shows a significant experimental variation with presentation rate but no such variation is predicted by theory. Second, randomly emptying the rehearsal buffer predicts incorrectly that the number of recalled items should be the highest when the first recalled item is the last list item. Third, a simplified Atkinson-Shiffrin model is found to predict exact relationships between the recall probabilities of the initial items which do not seem to be borne out by the Murdock data. Fourth, the theory predicts a discontinuity in the differences between free recall graphs with different presentation rates for early list items which is probably not found in the Murdock data

How Dreams And Memory May Be Related

I present a theory of dreams and long term memory structure that proposes that both entities are closely related. It is based on a variation of Freud's dream theory: (1) I re-label Freud's "Unconscious" the “Long Term Memory Structure” (LTMS), (2) I propose that dreams are ever present excitational responses to perturbations of perceptions and thought, during waking life as well as sleep, which only become conscious when the executive function of waking life ceases, and (3) I reinterpret Freud’s “Dream Work” as describing the pre-dream Storage Transformation of perceptions and thought into the LTMS. I make one further conjecture: Memories are stored in the LTMS according to what is already in the LTMS. The observables of Freud's theory remain the same. The new theory is also consistent with recent experimental findings and suggests a partial basis for personality: the selection process of the Storage Transformation

Properties of the Short Term Memory Structure

Properties of a short term memory structure are discovered in the data of Rubin, Hinton and Wenzel (1999): Cued-recall probability and search time are linearly related from 6 seconds to 666 seconds after stimulus presentation with a zero probability of cued-recall at 2.6 seconds and a 100% recall probability at 1.3 seconds. This linear relationship defines a short term memory structure which is a moving structure: the memory structure travels away from the starting point of the search (suggesting that the starting points of the search and storage are the same), decaying with a rate proportional to the time it takes to find the structure. The travel speed is slower than Brownian motion. The incorrect recall time saturates, giving an upper limit for the number of neurons involved in the short term memory structure of 3*108 using an interneuron transfer time or 4 msecs or 3*106 using an neuron-neuron transfer time of 20msecs