Cholecystokinin elicits the complete behavioral sequence of satiety in rats.

The behavior of intact rats and rats with chronic gastric fistulas was observed and scored during a 60-min test period when they were offered liquid diet after 17 hr of food deprivation. Intact rats and rats with closed fistulas displayed a specific behavioral sequence at the end of each meal: They stopped eating, engaged in grooming and exploration for a short time, and then rested or slept. Thus, a fixed behavioral sequence characterizes satiety in the rat. Although the behavioral sequence of satiety was fixed, the cessation of feeding was not a sufficient condition for the appearance of the rest of the sequence: Quinine adulteration of the liquid diet stopped sham feeding but did not elicit the complete sequence. Intraperitoneal injection of the intestinal hormone cholecystokinin during sham feeding, however, elicited the complete sequence of satiety. The observation that cholecystokinin not only stops feeding but elicits the complete sequence of satiety supports our hypothesis that endogenous cholecystokinin is a satiety signal for the rat.     

Methods for describing ordinal data with cardinal models

Several methods, both new and old, for describing ordinal data with a cardinal model are discussed in a newly developed and general context which broadens their applicability beyond their traditional use in multidimensional scaling. The relationships between the methods is investigated. It is shown that the two most commonly used methods (Guttman's rank-image principle and Kruskal's least-square monotonic transformation) are the boundary conditions of a newly proposed single parameter family of methods. An additional method is proposed which is shown to yield an equal-density model space. The commonly made distinction between “transformation” methods and “transformation-free” methods is shown to be a pseudodistinction. It is observed that all the methods can be stated as matrix operations on the model space with the conclusion that they try to optimize a linear combination of the model space.     

Recovery from adaptation as a function of stimulus orientation

These experiments examined the oblique effect in an adaptation paradigm. Reaction times (RT) to the presence of a grating test stimulus were obtained following adaptation to either a blank field or a grating of the same orientation as the test stimulus. Horizontal, vertical, and oblique test and adaptation orientations were employed. Test gratings were presented at several interstimulus intervals following offset of the adaptation stimulus. RTs following grating adaptation were elevated to a greater extent (relative to blank adaptation) for oblique then for horizontal or vertical stimuli, for two grating spatial frequencies. Differences in RT can be related to differences in sensitivity among channels responsible for detection of the various orientations.

     

Fluctuations in recall across successive test trials

The purpose of the experiment was to determine whether item fluctuation (intertrial forgetting and spontaneous recovery) depends upon the time allowed for recall and/or the demand characteristics of the experimental situation (manipulated via instructions to S). One hundred. and forty-four university undergraduates studied a 36-item list and then had two successive recall trials which were 9, 36, or 144 sec in duration. On the second recall trial, Ss were instructed to recall previously recalled items only (“old”), previously nonrecalled items only (“new”), or both previously recalled items and previously nonrecalled items (“both”). The results suggest two conclusions: (1) Although recall trial duration affects the overall amount of recall, it does not affect the amount of item fluctuation; and (2) an instruction to recall only “old” items or to recall only “new” items results in suppression of the nonrequested items without a corresponding facilitation for the requested items.     

The comprehension of relative,absolute, and contrastive adjectives by young children

Three types of adjectives-relative, contrastive, and absolute-were presented in standard and comparative contrasts to preschool children in a picture-choice paradigm. Proportion of errors in picture choices showed the predicted effect of greater difficulty for comparative than for standard terms. Latency data showed that the responses to comparative forms of absolute and contrastive adjectives were significantly slower than responses to their standard forms, and were also slower than responses to the comparative forms of the relative terms which did not differ from their standard forms. These data support the interpretation that the classes of relative, contrastive, and absolute adjectives are processed differently by young children. Factors of cognitive complexity that influence the order of difficulty are considered.     

Stereoscopic acuity for photometrically matched background wavelengths at scotopic and photopic levels

Two Ss made equidistance settings in a two-rod apparatus using white and four chromatic (red, yellow, Feen, and blue) backgrounds, photometrically matched at each of eight or nine teat levels within a total retinal-illuminance range of 4 log units. The binocular depth setting were analyzed in terms of the angular magnitude of both the Yariable error, η_AD, and the constant error, η_ΔR When η_AD is plotted as a function of retinal illuminance, the curves for each of the four chromatic IIIId white backlfound coditions show that at low retinal illuminances, η_AD, is initially large, and with increasing background illumination, η_AD progressively decreases to approach a final low asymptotic value. As predicted by the duplicity theory of vision, each experimental curve shows a dircontinulty at about ?1.0 lot td (corresponding to a background luminance value of about 0.0069 fL with the 2.5-mm artificial pupil used) reflecting the transition from rod to cone functioning. The curves representing the different wavelengths essentially overlap throughout the total illumination range, indicating that, for both rod and cone vision, wavelength has no differential effect on the variability of depth settings. The data for η_ΔR are less regular than those for η_AD and the rod-cone discontinuities appear less pronounced. The data are analyzed in terms of the relative contribution of the rod and cone mechanisms to performance level.     

Note on the invariance of response latency in shuttlebox avoidance learning

Rats trained to avoid shock by running in a shuttlebox showed an orderly increase over trials in the probability of avoidance but no corresponding change over trials in the latency of the avoidance response. Both responding in the presence of shock (escapes) and responding prior to shock onset (avoidances) appeared to be stationary in time. Latencies were found to vary with different experimental conditions but in every case to be invariant over trials.