Learning in mature mice (Peromyscus leucopus) subjected to deep hypothermia as neonates

In certain species of nonhibernating rodents, although young nestlings cease breathing and heart action when their body temperature is lowered to near freezing, the nestlings need only be rewarmed to recover. This remarkable capacity for immediate recovery has been known many years, but long-range consequences of deep neonatal hypothermia have never before been investigated. Mice (Peromyscus leucopus) that had been exposed to four 2.5-hr episodes of deep (2-4 degrees C) hypothermia when 4-10 days old were later compared with littermate controls in their performance on two learning tasks. The two groups did not differ in their acquisition or extinction of a lithium-induced learned taste aversion to sucrose. Nor did they differ in learning to find a hidden platform in a swimming pool. Thus in a nonhibernating rodent species, deep hypothermia experienced neonatally--unlike similar hypothermia administered in adulthood--seems not to induce deficits in subsequent learning capabilities. The resistance of neonates to damage probably represents an adaptation, for their modest thermoregulatory abilities render them vulnerable to deep hypothermia in frigid environments.     

Rhythm and the timing of movement sequences

Summary Many motor skills involve a sequence of movements phased over a period of time. The present study investigated the importance of rhythmic timing structures in the acquisition and control of a serial key-pressing task. Four groups of subjects received extensive practice on 9-element finger sequences varying in the form of the inherent temporal structure. Following a training period, the stability of the various timing patterns was examined by requiring subjects to perform the key-pressing task concurrently with a verbal memory task. The memory task involved reporting back a sequence of visually-presented words with a lag of one word. A comparison was made of performance on the two tasks under dual task and control (single task) conditions. The results suggested that natural rhythmic timing structures require less attention for production than unnatural temporal patterns. A breakdown of the temporal patterns into within-group and between-group intervals showed that patterns containing within-group intervals that related as 1:1 or 1:2 evidenced good stability under dual-task conditions. These results were taken as support for the suggestion by Fraisse (1946) that the perception and production of rhythms can be understood by an internal representation that allows only two distinct durations that relate as 1:2. Furthermore, it was suggested that relative timing may become an invariant property of motor program representation only in those instances in which the timing sequence completely fits the internal timing structure.     

Neonatal responsiveness as a function of maternal contact and obstetrical drugs

This work was designed to study changes in neonatal behavior during the first two days of life. Infants in Part I were from middle-class backgrounds. Half of these infants had unrestricted maternal contact during the first two days of life, the other half had contact with their mothers only at feeding time. Infants in Part II were from low socio-economic backgrounds. They were cared for entirely by the nursery staff during the first two days of life, so that differences in maternal style did not affect their behavior. Half of these babies were born to mothers who received 50 mg meperidine during labor, half to mothers who received no meperidine. This work provided evidence for the sensitivity of the neonate during the first two days of life. Both those infants who received unrestricted maternal contact and those whose mothers had received no obstetrical drugs exhibited more behavioral change than those who received low maternal contact or whose mothers had received meperidine during labor. High maternal contact and absence of obstetrical drugs also resulted in increased sensitivity to some environmental stimuli.     

Modeling a tactile sensory register

A detailed analysis was made of the data of a previous paper by Bliss et al (1966). That paper describes a series of experiments, in which 2 to 12 simultaneous air-jet stimuli were presented on the 24 phalanges of both hands. In addition, new data from an early blind S, whose performance was significantly better, is compared to the data of the original four Ss. Memory properties of all five Ss estimated by whole- and partial-reporting techniques gave evidence for a tactile short-term memory that (1) has a duration of a few seconds, (2) varies considerably in size (but not in temporal characteristics) for different Ss, and (3) has a capacity limited by spatial resolution. Tactile masking did not account for the limited spatial resolution, but a stimulus-spreading (or lateral-excitation) model did.     

Comparisons of stimulus learning and response learning in a punishment situation

These experiments use a procedure in which a rat is trained to make two topographically distinct responses on a single manipulandum, and then one of the responses is punished. Differential suppression of the punished response is taken as evidence of response learning, whereas the common suppression of both responses is attributed to stimulus learning or to general and nonassociative factors. Thus, this procedure begins the experimental separation of animals learning about the consequences of their behavior and animals learning what happens in a particular environment. A further separation is effected by using two such manipulanda; this procedure begins to distinguish between stimulus learning about the manipulandum and the more gereral factors that cause suppression. Some parameters affecting the relative importance of stimulus learning and response learning are examined.     

Role relevant sex typing and opportunity in agentic and communal domains1

The hypothesis associating psychological androgyny with greater personal adjustment has recently been contradicted in several studies in which masculine individuals, regardless of gender, generally appeared to be better adjusted than either androgynous or feminine persons. In the present research, five studies involving 363 subjects tested the hypothesis that such data may reflect a culture that values and differentially rewards agentic (masculine) characteristics and competencies in both men and women while taking communal (feminine) characteristics somewhat for granted. Subjects evaluating candidates for agentic roles preferred masculine candidates (regardless of gender). Masculine and androgynous persons were preferred for a communal role, while feminine persons were almost never chosen for either agentic or communal roles.     

Conceptual differentiation, integration and empathic prediction

Several investigators have examined the relationship of a rater's cognitive complexity to accurate empathic prediction of a target's self-concept or behavior, with mixed results. The present study sought to clarify this relation by considering both the conceptual differentiation (functionally independent construction) and integration (ordination) of both rater and target as they bear on predictive accuracy at early and later stages of acquaintance. Two sets of ten subjects participated in weekly self-disclosure groups, and attempted to predict one another's self-ratings on personal constructs after four and eighteen weeks of structured dyadic interaction. Results suggested that (a) the conceptual structure of the rater was unrelated to predictive accuracy, (b) high differentiated/low integrated targets were less accurately predicted at Time 1, (c) raters generally became more accurate predictors over time, and (d) conceptual structure was related to predictive accuracy at early, but not advanced stages of relationship. These findings were interpreted within an expanded theoretical framework emphasizing the multidimensional assessment of cognitive complexity as well as the stage of acquaintance at which social prediction takes place.     

Ontology-free modal semantics

The problem with model-theoretic modal semantics is that it provides only the formal beginnings of an account of the semantics of modal languages. In the case of non-modal language, we bridge the gap between semantics and mere model theory, by claiming that a sentence is true just in case it is true in an intended model. Truth in a model is given by the model theory, and an intended model is a model which has as domain the actual objects of discourse, and which relates these objects in an appropriate manner. However, the same strategy applied to the modal case seems to require an intended modal model whose domain includes mere possibilia.Building on recent work by Christopher Menzel (Nous 1990), I give an account of model-theoretic semantics for modal languages which does not require mere possibilia or intensional entities of any kind. Menzel has offered a representational account of model-theoretic modal semantics that accords with actualist scruples, since it does not require possibilia. However, Menzel's view is in the company of other actualists who seek to eliminate possible worlds, but whose accounts tolerate other sorts of abstract, intensional entities, such as possible states of affairs. Menzel's account crucially depends on the existence of properties and relations in intension.I offer a purely extensional, representational account and prove that it does all the work that Menzel's account does. The result of this endeavor is an account of model-theoretic semantics for modal languages requiring nothing but pure sets and the actual objects of discourse. Since ontologically beyond what is prima facie presupposed by the model theory itself. Thus, the result is truly an ontology-free model-theoretic semantics for modal languages. That is to say, getting genuine modal semantics out of the model theory is ontologically cost-free. Since my extensional account is demonstrably no less adeguate, and yet is at the same time more ontologically frugal, it is certainly to be preferred.Special thanks to Brian Chellas, Charles Chihara, Harry Deutsch, Bernard Linsky, Kirk Ludwig, Christopher Menzel and Gila Sher for helpful discussion. My thanks also to an anonymous referee for this Journal for kind words and attention to detail. Portions of this paper were presented at the 1993 meeting of the Society for Exact Philosophy in Toronto, and at the 1994 conference of the Association for Symbolic Logic in Gainesville, Florida. Thanks to all who attended those sessions.     

Displaying and Deciding Substructural Logics 1: Logics with Contraposition

Many logics in the relevant family can be given a proof theory in the style of Belnap's display logic (Belnap, 1982). However, as originally given, the proof theory is essentially more expressive than the logics they seek to model. In this paper, we consider a modified proof theory which more closely models relevant logics. In addition, we use this proof theory to show decidability for a large range of substructural logics.