Nosology and Causal Necessity; The Relation BetweenDefining a Disease and Discovering its Necessary Cause

The problem of disease definition is related to theproblem of proving that a certain agent is thenecessary cause of a certain disease. Natural kindterms like rheumatoid arthritis and AIDS refer toessences which are discoverable rather thanpredeterminate. No statement about such diseases isa priori necessarily true. Because theories onnecessary causes involve natural kind semantics,Koch's postulates cannot be used to falsify or verifysuch theories. Instead of proving that agent A is thenecessary cause of disease D, we include A in atheoretical definition of D, take this to representthe real meaning of D, and discard thepretheoretical definition. This is illustrated byKoch's own attempt to prove he had discovered thenecessary cause of tuberculosis. Methodologicalarguments about disease causation require a clear viewof our use of diagnostic terms. Medical lexicographersshould do more to provide such a view.     

Naming versus matching in color constancy

In this paper, a replication of the color-constancy study of Arend and Reeves (1986) is reported, and an alternative method is presented that can be used for the study of higher order aspects of color constancy, such as memory, familiarity, and perceptual organization. Besides a simultaneous presentation of standard and test illuminants, we also carried out an experiment in which the illuminants were presented successively. The results were similar to Arend and Reeves’s; however, in the object-matching condition of the successive experiment, we found an overestimation, instead of an underestimation, of the illuminant component. Because the results of matching experiments are difficult to interpret, mainly due to their sensitivity to instruction effects, we introduced another type of color-constancy task. In this task, subjects simply named the color of a simulated patch. It was found that, by applying such a task, a reliable measure of the degree of identification of object color can be obtained.     

An Implicit Theory of Intelligence-Related Mental Activities

ABSTRACT Mental act verbs are used to study implicit theories of intelligence as represented by mental activities. First, the multidimensional structure of the verbs was studied using a sorting task. The resulting structure was interpreted primarily in terms of three properties: a working property that refers to the operational aspect of information processing (and that is closely related to depth of a cognitive activity), a judgment property, and a creativity property. Second, the notion of intelligence was projected onto the structure, rating the verbs to determine how much intelligence they represented. We discovered that mental activities scoring high on intelligence were related primarily to the working property and to in-depth processing.     

Gamma-L-glutamyl-L-aspartate, interacting with NMDA receptors, affects appetitive visual discrimination tasks in mice.

gamma-L-glutamyl-L-aspartate (gamma-LGLA), which interacts with NMDA receptors, has been shown to impair retention of an active avoidance task in mice. Here, we specified the behavioral effects of gamma-LGLA on acquisition and retention of appetitive nondelayed visual discrimination tasks. Three experiments were conducted: the peptide (0.25 and 2.5 microM/kg/25 ml. ip) was administered 3 min after each of the first six sessions of either original learning, reversal 1 or reversal 3. gamma-LGLA affected acquisition of the original task and of the first reversal, as revealed by an absence of improvement on initial sessions and an increased number of sessions to reach criterion fixed at 7 of 10 correct choices on three consecutive sessions. This deficit did not result from an action of the peptide on position habits (repetition of spatial choices) nor on motivational processes, suggesting a specific interference of gamma-LGLA with acquisition and memorization of the visual rule. In contrast, gamma-LGLA had no effect on acquisition of the third reversal, in which the positively reinforced visual stimulus was identical to that used on the first reversal. These results show that the behavioral deficits of gamma-LGLA, which had previously been demonstrated in an aversive task, can be generalized to appetitive tasks based on acquisition of a new rule.     

Self-control in male and female rats

Eight male and 8 female Wistar rats were exposed to a discrete-trial procedure in which they chose between the presentation of a small (one pellet) or a large (three pellets) reinforcer. The delay to the small and large reinforcer was 6.0 s in the first condition of Experiment 1. Subjects consistently chose the large reinforcer. When the delay to the small reinforcer was decreased to 0.1 s in the next experimental condition, all subjects continued to choose the large 6.0-s delayed reinforcer. When the contingencies correlated with the two levers were reversed in the next experimental condition, the majority of subjects (5 males and 6 females) still chose the large delayed reinforcer over the small immediately presented reinforcer. The delay to the small reinforcer was maintained at 6.0 s, but the delay to the large reinforcer was varied among 9.0, 15.0, 24.0, and 36.0 s in Experiment 2, in which 4 males and 4 females participated. Most subjects consistently chose the large increasingly delayed reinforcer, although choice for the small 6.0-s delayed reinforcer developed in some females when the large reinforcer was delayed for 24.0 or 36.0 s. These choice patterns were not predicted from a literal application of a model that says choice should favor the alternative correlated with the higher (amount/delay) ratio.