On the relation between similarity and ratio estimates

Summary Data obtained in four sets of experiments involving pitch, heaviness, greyness, and circular area were re-analyzed. It was found (1) that similarity estimates S _ijare a power function of stimulus ratios S _ijwith the exponent n _s,(2) that ratio estimates q _ijare also a power function of stimulus ratios S _ijwith the exponent n _q(i.e., Stevens' power law), (3) that the exponent n of similarity estimates as power function of ratio estimates is equal to the ratio n _s/n _q,and (4) that, inversely, the exponent m of ratio estimates as power function of similarities is equal to the ratio n _q/n _s.The investigation was supported by a grant from the Swedish Council for Social Science Research.     

Deprivation and satiation: The interrelations between food and wheel running

Two experiments were designed to assess whether depriving rats of food would increase the reinforcement effectiveness of wheel running (Experiment 1) and whether satiation for wheel running would decrease the reinforcement effectiveness of food (Experiment 2). In Experiment 1, a progressive-ratio schedule was used to measure the reinforcement effectiveness of wheel running when rats were deprived or not deprived of food. Completion of a fixed number of lever presses released a brake on a running wheel for 60 s, and the response requirement was systematically increased until the rat stopped pressing or until 8 hr had elapsed. The ratio value reached (and the total number of lever presses) was an inverted-U function of food deprivation (percentage body weight). In Experiment 2, when wheel running preceded test sessions, fewer food-reinforced lever presses were maintained by the progressive-ratio schedule, and responding occurred at a lower rate on a variable-interval schedule. An interpretation of these results is that deprivation or satiation with respect to one event (such as food) alters the reinforcement effectiveness of a different event (such as access to wheel running).     

On the similarity of features

Tversky's featural contrast model for similarity judgments is discussed and its featural definition of entities and Boolean characterization of judgments are criticized. Features are themselves identified on the basis of appraisals of similarity and so cannot be defined in an a priori or context-free manner. Tversky's model may assist the discovery of orderly psychological patterns, but misses the central cognitive issues of concern. Empirical findings relevant to this critique are reviewed. The criticisms of Tversky's model lead to a more general critique of the representational-computational model of mind and its associated methods.     

Category-based induction from similarity of neural activation

The idea that similarity might be an engine of inductive inference dates back at least as far as David Hume. However, Hume’s thesis is difficult to test without begging the question, since judgments of similarity may be infected by inferential processes. We present a one-parameter model of category-based induction that generates predictions about arbitrary statements of conditional probability over a predicate and a set of items. The prediction is based on the unconditional probabilities and similarities that characterize that predicate and those items. To test Hume’s thesis, we collected brain activation from various regions of the ventral visual stream during a categorization task that did not invite comparison of categories. We then calculated the similarity of those activation patterns using a simple measure of vectorwise similarity and supplied those similarities to the model. The model’s outputs correlated well with subjects’ judgments of conditional probability. Our results represent a promising first step toward confirming Hume’s thesis; similarity, assessed without reference to induction, may well drive inductive inference.     

Effector localization and transfer of reactive inhibition

An experimental test was made of Hull's (1943) notions that reactive inhibition is effector-specific and that it has primary negative motivational properties. Four groups of 20 subjects (10 males and 10 females in each) executed two segments of continuous right-hand practice on a mirror-tracking task. The two segments were separated either by 0 min rest, 5 min rest, 5 min continuous right-hand practice on rotary pursuit, or 5 min continuous left-hand practice on rotary pursuit. Effects of interpolated conditions were measured in terms of main-task reminiscence arid initial post-treatment performance. When interpolated practice was conducted with the right hand, reminiscence and post-treatment performance were significantly depressed relative to the rest effect, but not when interpolated practice was conducted with the left hand. Thus, Hull's views were supported, while competing views, such as the task specificity concept of lr and the consolidation theory of reminiscence, were impugned.     

Resistance to satiation: Reinforcing effects of food and eating under satiation

It has been shown previously that rats which have learned a response when hungry will continue to make that response when tested satiated, a phenomenon labeled resistance to satiation. Here we showed that rats which were previously trained hungry will learn a new response for the opportunity to consume pellets in a new situation when tested satiated. In four experiments various groups received each of the components of the training given when rats learn an instrumental response when hungry. Rats were placed in the goalbox of a straight alley and given food pellets when hungry or were hungry only in their home cages prior to running a straight alley in the satiated test in Experiment 1. In Experiments 2, 3, and 4 learning of a differential conditioning problem for pellets in S+ (nonreward in S?) was measured in the satiated test. Groups given pellets in their home cages when hungry with or without alley exposure learned to run more rapidly in S+ than in S? in the satiated test phase. The tendency to eat pellets in the apparatus and the reinforcing effect of eating the pellets was larger for rats which ate the pellets when hungry in their home cage than for rats which ate the pellets when satiated in their home cage. Being hungry in the home cage with no pellets was not sufficient to produce eating or running for pellets in the satiated test, indicating that any inherent reinforcing effect of the pellets is not sufficient to produce eating or running, and that incomplete satiation cannot account for the learning. These data indicate that a reinforcing effect of eating pellets under satiation is an important determiner of resistance to satiation.     

Food satiation in the pigeon

The experiment was designed to find the shape of food satiation curves of the pigeon as a function of hours of deprivation or percentage of free-feeding weight, and to study the fluctuation in free-feeding weight as a function of deprivation and satiation. At a systematically and progressively increased number of hours'' deprivation, eight birds were allowed to satiate on grain presented contingent upon the emission of a pecking response. In the second part of the experiment, in which two birds were used, a similar procedure was followed except that the independent variable was percentage of free-feeding weight. These were the conclusions.1. Approximately 64% of the satiation curves were classified as straight with an abrupt stop. The next highest percentage of curves was 18% for curves classified as straight with a curvilinear stop. No “classic” satiation curves, curvilinear with curvilinear stop, were found.2. The pigeons responded at fairly constant rate during the early part of each satiation session, or they did not respond at all. The critical weight, above which they did not respond, was 85% of free feeding.