Patrick J. Capretta

Selective herbivory in tassel-eared squirrels: role of monoterpenes in ponderosa pines chosen as feeding trees.

Ponderosa pine twigs collected from trees used by tassel-eared squirrels as sources of cortical tissue for food contained smaller amounts of monoterpenes than twigs from similar trees not used by the squirrels as food sources. Of the 18 monoterpenes isolated from the twig samples, α-pinene was the best single predictor of food source trees. In experiments with captive tassel-eared squirrels, consumption of a preferred food was inversely correlated with the concentration of α-pinene added to the food.

Saccharin and saccharin-glucose ingestion in two inbred strains of Mus musculus

In one experiment 10 C57BL/6J and 10 DBA2/J mice received saccharin in daily 1/2-h sessions for 19 days while hungry or satiated. A second experiment involved giving these same mice saccharin or glucose and saccharin plus glucose for 24-h periods with or without solid food. It was found in Experiment 1 that saccharin consumption is related to drive; hungry mice at first drank more than did nonhungry mice until the 11th day, after which the former group dropped off and was equalled by the latter. The effect was more pronounced for C57 than for DBA mice—apparently related to strain differences in natural preferences for saccharin. Both strains drank large amounts of saccharin plus glucose in Experiment 2, especially when hungry. The results are discussed within the context of research on food habits.

Establishment and Modification of Food and Taste Preferences: Effects of Experience

Summary Restricting an animals diet early in life to a single food or flavor serves to enhance the preference value of that substance later in life. A primacy effect is most clearly found in precocial species, such as the domestic chicken; results for late maturing species is less certain. As for changes in food preferences, a chief concern is with the relationship between the kinds of cues involved in the aversive conditioning of food preferences. A theory of stimulus relevance indicates the likelihood of gustatory-olfactory cues becoming aversively conditioned to gastrointestinal discomfort, and auditory-visual cues to pain from electric shock. This suggests that learned associations—at least for the rat—are facilitated by a naturally occurring compatibility between exteroceptive events, such as color and shock, and between other events (e.g., flavor and gastrointestinal pain) functioning interoceptively. Furthermore, those associations between irrelevant events may be mediated by associations between ...

Changes in colored or flavored food preferences in chickens as a function of shock

Twenty-four two-week old chicks were first tested to determine which of two mashes, differing either in color or in taste only, was preferred; Ss were then trained such that the Experimentals received a painful leg shock when they ate their preferred food, while the Controls were either shocked in the absence of the test food or not shocked. Feeding on the nonpreferred food went undisturbed in all three groups. Several posttraining tests were given to detect any changes in colored or flavored food preferences. Electric shock proved to be an effective noxious stimulus for changing food preferences based on visual cues but not for those distinguishable by taste alone.

Discrimination reversal learning in the crayfish.

Summary Nine crayfish failed to show progressive improvement in learning over nine reversals in a two-choice spatial discrimination problem involving a non-correction procedure of training. The results are discussed in their relationship to the habit reversal data on other species.

Validity and Reliability of Certain Measures of Psychological Stress

In this study the appropriateness of a previously reported stress-sensitive measure was determined for a field situation involving a stressor with high face-validity. METHOD Subjects.-Two hundred Army recruits ( 120 Ss in the experimental group and 80 Ss in the control group) participated as Ss. Procedwe.-The suessor was a three-rope toggle bridge 200 ft. long and 50 fc. above a rocky ravine, over which Ss, wearing headsets wich earphone and microphone, were run individually. They were stopped midway for a recorded test (administered over the headsets) of immediate backward digit memory span. Another administration of an equivalent form was given either just before starting or just after crossing the bridge. Half of the experimental Ss were tested in each sequence. The control Ss were tested on, and before or after crossing a short mock bridge, approximately 1 fc. off the ground. Half of the control Ss were tested in each sequence also. Care was taken to space the rwo control testings so that the time-lapse between the first and second testing was similar to that occurring in the experimental condition. Little attempt was made to control for fatigue. Of the experimental Ss on the long, high bridge, 40 had had prior experience (earlier the same day) on a similar bridge not quite so long or high. The remaining Ss in this group were given no prior experience with bridge crossing. To facilitate the mechanical administration by tape recording, the digitspan test procedure was modified according to one described by Myers, Burday, Forbes, and Arbit ( 1958). Each adminiscration of the digit-span test consisted of two presentations each of seven different item-lengths (from 2 to 8 digits) in random order. Ss were required to recall each item bacbwurd immediately upon hearing a particular item-length. The digit-span test was chosen as a measure of the stress effect on the basis

Effects of hunger and thirst levels during sugar and sugar-saccharin consumption on later preferences

Sixteen mature male rats first received six daily 30 min tests to determine which of two solutions (10% sucrose or 10% sucrose + 0.1% saccharin) was preferred. Each S was then allowed to drink its nonpreferred solution before maintenance feedings on one day and its preferred solution after feedings on another day for 10 days of alternating 30 min trials. Posttests given on the five days following training failed to show any reliable changes in preferences. Such results suggest that a nonaversive training procedure is ineffective in changing the preference value of highly palatable foods.

Discrimination learning in chicks previously exposed to the discriminanda

Three experiments are described. The ability of chicks to discriminate shape or colored stimuli after being exposed to both discriminanda in an imprinting situation is compared with the discriminative ability of chicks not previously exposed. In two of the three experiments, we found no differences between the groups, although in the third, the group previously exposed to the discriminanda showed an impairment in discriminative ability. Our negative results are not in accordance with those of Bateson and Chantrey (1972), who attribute the learning impairment to a prior “classifying together” of the stimuli, a mechanism enabling the chick to respond to differing views of the imprinting object as representative of the same object.

Olfactory bulb removal and taste aversion learning in mice

Bulbectomized and unoperated mice were given 1 h of exposure to a novel food (almond) before receiving an intraperitoneal injection of lithium chloride solution. Their consumption of almond was recorded for the subsequent 10 days. Mice of both groups acquired a marked aversion to almond, and the unoperated mice continued to eat little throughout the experiment. The bulbectomized mice resumed eating more rapidly and, by the third day after the induction of illness, their consumption of almond did not differ from that of a control group which had not been lithium treated. The integrity of the olfactory system appears necessary for the maintenance, though not the establishment, of a taste aversion.

Auditory discrimination learning in chicks after exposure to auditory and visual stimuli

Bateson and Chantrey (1972) have shown a retardation of visual discrimination learning in chicks previously exposed to the discriminanda. They explained their results in terms of an imprinting mechanism whereby a young bird learns the various characteristics of an object and classifies them together. In the present study, chicks were exposed to 390 Hz, 295 Hz, 390 and 200 Hz, or “no sound” together with a flashing blue light. They were then required to learn to discriminate between 390 Hz and 200 Hz, with the light as reinforcer. There was no indication of classification together of the auditory stimuli or the auditory and visual stimuli. Few chicks, regardless of prior experience, learned the discrimination. Explanations for the inability to learn are proposed.