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PubMed1993

A protoconnectionist theory of memory.

I.A. Richards published a chapter entitled "Memory" in 1924 in which he proposed what may be viewed as the outline of a connectionist theory of memory. However, this protoconnectionist theory attracted no subsequent attention. There appear to be two types of reason for this neglect. The first concerns the impossibility at that time of implementing the theory in the form of an explicit model. The second concerns the nature of Richard's career. On the one hand, Richards did not himself subsequently develop his theory of memory any further. On the other, the fact that Richards was not generally perceived as a psychologist probably impeded the dissemination of his theory among psychologists. The neglect of Richards's theory demonstrates the range of factors, other than the strictly scientific, which can be important in determining the influence or otherwise of a psychological theory.

History, 19th Century↗
PubMed1997

Memory recovery and repression: what is the evidence?

Both the theory that traumatic childhood memories can be repressed, and the reliability of the techniques used to retrieve these memories are challenged in this paper. Questions are raised about the robustness of the theory and the literature that purports to provide scientific evidence for it. Evidence to this end is provided by the authors which surveyed New Zealand families in which one member had accused another (or others) of sexual abuse on the basis of recovered memories. It is shown that a number of these allegations involve very low probability events. Since memory repression theory is not currently scientifically substantiated it is argued that care needs to be taken in the mental health, legal and insurance compensation arenas. Memories recalled during therapy may be treated as metaphorical but, in the absence of corroborative evidence, should not be considered factually true. Clinicians who wish to use memory recovery techniques should inform patients of their experimental and controversial nature, point out adverse effects, and obtain consent before proceeding.

Child↗
PubMed2001

Signed Orders, Choice Probabilities, and Linear Polytopes.

Self-reflecting signed orders were proposed as an aid in estimating preference between subsets of items on the basis of limited information. The data of a signed order are preference comparisons that consider the desirability of excluding items from a subset as well as including items in a subset. This paper investigates signed orders within the setting of probabilistic choice and random utility theory. It focuses on linear signed order polytopes and their relationship to binary choice probabilities. The theory applies both to individual choice behavior and to group decision making. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Forecasting trial outcomes: lawyers assign higher probability to possibilities that are described in greater detail.

The study of judgment under uncertainty has revealed that people judge the probability of an event to be higher when the event is described as a disjunction of constituent events or when they judge constituent events separately. These observations have motivated the development of support theory (Y. Rottenstreich & A. Tversky, 1997; A. Tversky & D. J. Koehler, 1994), a descriptive model of judgment under uncertainty. The major predictions of support theory are that (1) the judged probabilities of complementary events sum to 1; (2) the judged probabilities of n > 2 exclusive and exhaustive events generally sum to more than 1; and (3) the judged probability of an event generally increases when it is described as a disjunction of specific possibilities. We test these predictions in 6 studies of experienced attorneys who judged the likelihood of particular trial outcomes or were asked to offer advice on whether or not to accept a settlement offer. The results demonstrate that attorneys are indeed susceptible to bias in forecasting trial outcomes, consistent with support theory.

Forecasting↗
PubMed2000

CPP calculation of multiple scattering distributions for charged particles penetrating compounds or mixtures.

Charged particle multiple scattering distributions may be constructed from individual atomic scattering events on the basis of compound Poisson process (CPP) theory. We present a CPP method for computing multiple scattering transition probability densities from charged particles penetrating compounds and mixtures. Water as a scattering medium provides here an example of the calculation method which is applicable to compounds or mixtures. Electrons are chosen as examples of charged particle beams. The Rutherford single scattering cross section and a partial wave analysis single scattering cross section are chosen as example cross sections. Transition probability densities predicted on the basis of CPP theory can be calculated with great accuracy for the improvement of radiation dose calculations. The advantages of the CPP method are (a) an effective atomic number need not be defined for the scattering medium, (b) it can be applied in both spherical and planar coordinate systems, and (c) it does not require any specific form for the single scattering cross section.

Algorithms↗
PubMed2005

Thermodynamic prediction of protein neutrality.

We present a simple theory that uses thermodynamic parameters to predict the probability that a protein retains the wild-type structure after one or more random amino acid substitutions. Our theory predicts that for large numbers of substitutions the probability that a protein retains its structure will decline exponentially with the number of substitutions, with the severity of this decline determined by properties of the structure. Our theory also predicts that a protein can gain extra robustness to the first few substitutions by increasing its thermodynamic stability. We validate our theory with simulations on lattice protein models and by showing that it quantitatively predicts previously published experimental measurements on subtilisin and our own measurements on variants of TEM1 beta-lactamase. Our work unifies observations about the clustering of functional proteins in sequence space, and provides a basis for interpreting the response of proteins to substitutions in protein engineering applications.

Amino Acid Substitution↗
PubMed1991

[Determinants of pride and shame: outcome, expected success and attribution].

In two experiments we investigated the relationship between subjective probability of success and pride and shame. According to Atkinson (1957), pride (the incentive of success) is an inverse linear function of the probability of success, shame (the incentive of failure) being a negative linear function. Attribution theory predicts an inverse U-shaped relationship between subjective probability of success and pride and shame. The results presented here are at variance with both theories: Pride and shame do not vary with subjective probability of success. However, pride and shame are systematically correlated with internal attributions of action outcome.

Achievement↗
PubMed2005

Constructivism, the so-called semantic learning theories, and situated cognition versus the psychological learning theories.

In this paper, the perspective of situated cognition, which gave rise both to the pragmatic theories and the so-called semantic theories of learning and has probably become the most representative standpoint of constructivism, is examined. We consider the claim of situated cognition to provide alternative explanations of the learning phenomenon to those of psychology and, especially, to those of the symbolic perspective, currently predominant in cognitive psychology. The level of analysis of situated cognition (i.e., global interactive systems) is considered an inappropriate approach to the problem of learning. From our analysis, it is concluded that the pragmatic theories and the so-called semantic theories of learning which originated in situated cognition can hardly be considered alternatives to the psychological learning theories, and they are unlikely to add anything of interest to the learning theory or to contribute to the improvement of our knowledge about the learning phenomenon.

Cognition↗
PubMed2006

Reasoning with conditionals: a test of formal models of four theories.

The four dominant theories of reasoning from conditionals are translated into formal models: The theory of mental models (Johnson-Laird, P. N., & Byrne, R. M. J. (2002). Conditionals: a theory of meaning, pragmatics, and inference. Psychological Review, 109, 646-678), the suppositional theory (Evans, J. S. B. T., & Over, D. E. (2004). If. Oxford: Oxford University Press), a dual-process variant of the model theory (Verschueren, N., Schaeken, W., & d'Ydewalle, G. (2005). A dual-process specification of causal conditional reasoning. Thinking &Reasoning, 11, 278-293), and the probabilistic theory (Oaksford, M., Chater, N., & Larkin, J. (2000). Probabilities and polarity biases in conditional inference. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 883-899). The first three theories are formalized as multinomial models. The models are applied to the frequencies of patterns of acceptance or rejection across the four basic inferences modus ponens, acceptance of the consequent, denial of the antecedent, and modus tollens. Model fits are assessed for two large data sets, one representing reasoning with abstract, basic conditionals, the other reflecting reasoning with pseudo-realistic causal and non-causal conditionals. The best account of the data was provided by a modified version of the mental-model theory, augmented by directionality, and by the dual-process model.

Adolescent↗
PubMed1999

Biological probability: cognitive processes of generating probabilities of events in biological systems.

This paper analyses relationships between probabilities of events happening in biological systems (or probabilistic disposition of systems) and cognitive properties of biological entities comprising such systems. Two kinds of cognitive properties are identified as relevant to the current problem: the ability to respond differently against different configurations of the environment (discriminability of cognition), and the ability to make an appropriate response to maintain a particular relation with the environment (selectivity of cognition). A basic framework bridging the two features of living systems, probabilistic disposition and the cognitive properties, is presented towards a general theory explaining the process generating probabilities of biological events. In this framework, a deterministic model of a system of entities is developed, in which objects are described as subjects that cognize events (i.e. entities as cognizers). Cognition is used in a wider sense, including not only biotic but also abiotic, and cognizers are conceptually distinguished from the meta-observer who describes the system externally. Based on this perspective, this paper seeks to explicate how events can occur in an uncertain, probabilistic manner, if observed from a cognizer viewpoint, even under a deterministic system. Each cognizer is identified with both the set of states that are actually taken, and its motion function which maps its state uniquely to a successor state depending on the current states of itself and of the rest of cognizers constituting the system. The model analysis reveals that the cognitive properties, discriminability and selectivity, of a cognizer can contribute to determining the probability of an event encountered by the cognizer itself-in particular, discrimination reducing the uncertainty in events occurrence for the cognizer. Biological implication of this result is discussed focusing on the concept of the probability of survival and reproduction.

Animals↗
PubMed1990

Ammon's horn sclerosis: its pathogenesis and clinical significance.

Sclerosis of the cornu Ammonis or Ammon's horn sclerosis (AHS) is an "often-described, yet hitherto enigmatic phenomena" as Spielmyer put it in 1927. It has been found in cases with ischemia, anoxia or hypoglycemia and in more than half of the epileptic brains examined at autopsy. Various theories about its pathogenesis have been propounded. Among them, the "Pathoklise" theory of the Vogts and the vascular theory of Spielmeyer and his associates were prevailing until recently. In 1953, two articles were published to contribute to the pathogenesis of ictal automatism (a type of complex partial or temporal lobe seizures). One is the incisural sclerosis theory by Penfield and his associates and the other is the Ammon's horn sclerosis theory by Sano and Malamud. The former authors described a diffuse sclerosis of the infero-mesial temporal structures without, however, specifically relating it to AHS. They considered it was the result of localized anoxia of that portion of the brain caused by incisural herniation occurring during parturition. Sano and Malamud maintained that AHS is a result of convulsions, a distinct scar adjacent to which epileptogenic foci may develop in the course of time to cause ictal automatism. The latter theory was corroborated by Sano, Falconer and others. Falconer expanded the theory to the assertion that not only ictal automatism but other types of intractable epilepsy may be due to "mesial temporal (Ammon's horn) sclerosis". The most recent development in the pathogenesis of AHS is the excitotoxicity theory. Namely, AHS is caused by excessive excitation of neurons, probably by putative excitatory neurotransmitters, especially, glutamate. For this theory, there is a significant body of evidence. The problem of AHS, an old research subject and a matter of long-lasting controversy, has now been updated and become one of the newest topics in the field of experimental neurobiology.

Animals↗
PubMed1993

An exact algebraic theory of genetic drift in finite diploid populations with random mating.

We study random mating in a finite diploid monoecious population with two alleles at one locus. We take into account selection and a constant probability of self-mating. The generations are assumed discrete (non-overlapping). An exact algebraic theory of genetic drift is developed by the technique of transition probability matrices. The theory works on the genotype level (Hedrick, 1970), but also allows the population size to vary from generation to generation. Thus, it gives an exact statistical description of bottleneck processes, as an inhomogeneous Markov chain. Numerical Monte Carlo simulations are performed and give full agreement with the present algebraic theory. The decay rates for heterozygosity agree with the asymptotic theory by Wright (1931).

Animals↗
PubMed1986

Do mental events cause neural events analogously to the probability fields of quantum mechanics?

If non-material mental events, such as the intention to carry out an action, are to have an effective action on neural events in the brain, it has to be at the most subtle and plastic level of these events. In the first stage of our enquiry an introduction to conventional synaptic theory leads on to an account of the manner of operation of the ultimate synaptic units. These units are the synaptic boutons that, when excited by an all-or-nothing nerve impulse, deliver the total contents of a single synaptic vesicle, not regularly, but probabilistically. This quantal emission of the synaptic transmitter molecules (about 5000-10 000) is the elementary unit of the transmission process from one neuron to another. In the second stage this refined physiological analysis leads on to an account of the ultrastructure of the synapse, which gives clues as to the manner of its unitary probabilistic operation. The essential feature is that the effective structure of each bouton is a paracrystalline presynaptic vesicular grid with about 50 vesicles, which acts probabilistically in vesicular (quantal) release. In the third stage it is considered how a non-material mental event, such as an intention to move, could influence the subtle probabilistic operations of synaptic boutons. On the biological side, attention is focused on the paracrystalline presynaptic vesicular grids as the targets for non-material mental events. On the physical side, attention is focused on the probabilistic fields of quantum mechanics which carry neither mass nor energy, but which nevertheless can exert effective action at microsites. The new light on the mind-brain problem came from the hypothesis that the non-material mental events, the 'World 2' of Popper, relate to the neural events of the brain (the 'World 1' of matter and energy) by actions in conformity with quantum theory. This hypothesis that mental events act on probabilistic synaptic events in a manner analogous to the probability fields of quantum mechanics seems to open up an immense field of scientific investigation both in quantum physics and in neuroscience.

Animals↗
PubMed1994

Simple stochastic theory of stem cell differentiation is not simultaneously consistent with crypt extinction probability and the expansion of mutated clones.

It is shown that a simple Galton-Watson branching process model of the stem-cell pool in intestinal crypts is not simultaneously consistent with observations of the dynamics of replacement of normal by mutant crypt stem cells and other observations which put limits on the probability of crypt loss through extinction of all stem cells. This is because the limits on extinction probability forces the probability that a stem-cell division yields only non-stem cells to be small, but such a small probability makes it unlikely that a mutant stem-cell clone would expand while the normal stem-cell clones decay (it is more likely that both normal and mutant clones persist). It is suggested that the fundamental assumptions of independence and constancy of stem-cell behavior are flawed.

Cell Differentiation↗
PubMed2002

Lévy processes in free probability.

This is the continuation of a previous article that studied the relationship between the classes of infinitely divisible probability measures in classical and free probability, respectively, via the Bercovici-Pata bijection. Drawing on the results of the preceding article, the present paper outlines recent developments in the theory of Lévy processes in free probability.

Journal Article↗
PubMed1990

Probabilistic secretion of quanta from nerve terminals at synaptic sites on muscle cells: non-uniformity, autoinhibition and the binomial hypothesis.

A model of the secretion of a quantum at a release site is proposed in which, following the influx of calcium ions, synaptic vesicles are made available for release by the activation of kappa phosphorylation steps with rate alpha. At any time during this process the vesicles may become unavailable for secretion at rate gamma. On completion of the kappa phosphorylation steps the vesicles participate in the formation of a fusion pore with the terminal membrane to give exocytosis at rate delta. Changes in alpha, delta and kappa are shown to produce characteristic changes in the number and timecourse of quantal secretions following a nerve impulse, which are similar to those observed following drug treatments that are thought to act selectively on each of these processes. The number of quanta secreted from nerve terminals that consist of many release sites does not fluctuate much during a low frequency train of impulses: the variance is small compared with the mean level, so secretion follows binomial rather than Poisson statistics. A theory is derived that shows that variations in the probability of secretion amongst these release sites of any particular kind fails to reduce the variance of the total secretion from the terminal; Poisson rather than binomial statistics then still apply. The theory shows that an interaction between release sites is required to reduce this variance and such an effect is provided if secretion at a site inhibits secretion at nearby sites. Simulations show that incorporating this process of autoinhibition into the model reproduces the experimental observations on the effects of calcium ions on the binomial parameters p and n as well as on the relative constancy of p during facilitation and depression of quantal secretion. Methods for estimating the timecourse of changes in the probability of secretion at release sites following an impulse, by using either the time of occurrence of first, second, third or later quantal latencies, are given. These procedures show that current methods for estimating the time-dependent probability changes are inadequate for detecting interaction between release sites, such as autoinhibition, unless this is relatively large. Therefore, estimates from third quantal latencies are used.

Animals↗