Preference for novel flavors in adult golden hamsters ( Mesocricetus auratus ).

Although animals generally prefer to eat foods with familiar rather than unfamiliar flavors, adult golden hamsters (Mesocricetus auratus) were found to do the opposite. After having prolonged exposure to a food with a particular flavor, hamsters were allowed to select between the food with the familiar flavor and the same food with a novel flavor. Hamsters consistently ate more of the food with the novel flavor, and this preference was long-lasting and resistant to extinction. Furthermore, the novelty effect was robust, being manifested in both sexes and under a variety of experimental circumstances. In contrast, rats tested under identical conditions consistently preferred the food with the familiar flavor. The origins of the novelty effect in hamsters remain to be determined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences Between Golden Hamsters (Mesocricetus auratus) and Norway Rats (Rattus norvegicus) in Preference for the Sole Diet That They Are Eating.

D. DiBattista (2002) reported that hamsters but not rats showed reduced preferences for the sole diet they had eaten for 10 days. In the current study, the authors fed Norway rats (Rattus norvegicus) a nutritious diet for either 3 or 10 days, then tested them either immediately or 1 or 3 days later. The authors found that like golden hamsters (Mesocricetus auratus), rats exhibited reduced preferences for a prefed diet but only if tested either immediately or 1 day after prefeeding, not if tested 3 days later (when D. DiBattista tested his hamsters). Rats and hamsters differed in the longevity, not the development, of reduced preferences for a palatable food eaten for several consecutive days. Such a response might aid dietary generalists in constructing balanced diets when no single available food is nutritionally adequate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconditioned sexual incentive motivation in the male Norway Rat (Rattus norvegicus).

Sexual incentive motivation was evaluated in a procedure consisting of a large open field where incentive animals were confined behind wire mesh openings. When sexually inexperienced male rats (Rattus norvegicus) were exposed to the receptive female-male incentives, they spent more time close to the female. If the incentives were receptive female-nonreceptive female, the receptive female was preferred. However, when the alternatives were nonreceptive female-male, no preference was obtained. Castration abolished preference for the receptive female, and treatment with testosterone propionate restored it. Estradiol plus oil is as efficient as estradiol plus progesterone for giving the ovariectomized female incentive properties. The living female can be replaced with female odor. Sexual experience did not have any long-term effects on the female's incentive value, but immediately preceding limited sexual activity enhanced it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lack of Interference in Long-Term Memory for Socially Learned Food Preferences in Rats (Rattus norvegicus).

Outside the laboratory, rats (Rattus norvegicus) are likely both to interact with several conspecifics that have eaten various foods and to eat a variety of foods themselves before they encounter any particular food for which they have a socially enhanced preference. Here the authors examine the stability of rats' socially learned food preferences following 6 days of potentially disruptive ingestive experiences. The authors found that 6 days of (a) eating unfamiliar foods, (b) interacting with demonstrators that had eaten unfamiliar foods, or (c) both eating unfamiliar foods and interacting with demonstrators that had eaten those foods had no measurable effect on rats' socially learned food preferences. The stability of socially enhanced food preferences over time and despite potentially disruptive experiences is consistent with the view that social learning about foods is an important determinant of the food choices of free-living Norway rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraventricular Insulin and Leptin Reverse Place Preference Conditioned With High-Fat Diet in Rats.

The authors hypothesized that insulin and leptin, hormones that convey metabolic and energy balance status to the central nervous system (CNS), decrease the reward value of food, as assessed by conditioned place preference (CPP). CPP to high-fat diet was blocked in ad-lib fed rats given intraventricular insulin or leptin throughout training and test or acutely before the test. Insulin or leptin given only during the training period did not block CPP. Thus, elevated insulin and leptin do not prevent learning a food's reward value, but instead block its retrieval. Food-restricted rats receiving cerebrospinal fluid, insulin, or leptin had comparable CPPs. Results indicate that the CNS roles of insulin and leptin may include processes involving memory and reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Positive Geotaxis in Infant Rats (Rattus norvegicus) : A Natural Behavior and a Historical Correction.

Infant rats (Rattus norvegicus) placed on a shallow incline (2°, 4°, or 8°) oriented and moved downhill within 1 min; that is, they displayed positive geotaxis. Their downhill translocation increased with angle of inclination. A variety of possible behavioral elements (e.g., initial orientation, rotational movements, ambulatory velocities) were eliminated as explanations of the geotaxis. Wall contact was recognized as a determinative event: Pups on the inclines showed no orientation with respect to the geogravitational stimulus before contacting a wall. The event of wall contact, however, evoked reliable downhill orientation and more linear movements. Positive geotaxis was created by pups' orientation against walls and an associated increase in movement velocity. This is a distinct perspective on a behavioral response that replaces a traditionally misinterpreted phenomenon. The authors discuss the ecological validity and historical context of these findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preference for symmetry is experience dependent in newborn chicks (Gallus gallus).

Spontaneous pecking preferences toward symmetric or asymmetric stimuli were tested in newborn chicks (Gallus gallus). A preference for asymmetric patterns was found in na?ve chicks (either 24 or 48 hours old), although a preference for symmetry appeared at retest after chicks had experienced standard rearing conditions (Experiments 1 and 2). Only food-experienced chicks preferred symmetric patterns; food-deprived and hand-fed chicks did not show any preference (Experiment 3). A key factor that allowed for the emergence of a preference for symmetry may relate to the improving of pecking sensorimotor skills occurring during active food manipulation. Possible explanations are discussed for the late emergence of the preference for symmetry and for the preference for asymmetry found in na?ve chicks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interdose interval effects on the development of contextual tolerance to nicotine's analgesic effects in rats (Rattus norvegicus).

Learning models of associative and nonassociative drug tolerance predict that the development of contextual tolerance to drug effects is disrupted when the drug is delivered at short interdose intervals (IDIs). The authors examined the impact of 1 long IDI and 2 short IDIs in the development of contextual nicotine tolerance. Associative tolerance was investigated by giving rats (Rattus norvegicus) 10 subcutaneous injections of nicotine at either long (72-hr) IDIs or short (6-hr and 4.5-hr) IDIs. The delivery of nicotine was either explicitly paired or explicitly unpaired with a distinctive context. A 3rd group of rats was exposed to the experimental procedures but received only saline. Associative tolerance to nicotine's analgesic effects was defined as a shift to the right of the dose-response curve (DRC) of rats in the explicitly paired condition with respect to the DRC of rats in the explicitly unpaired condition. Analgesia was assessed with the tail-flick and hot-plate devices. In the tail-flick assessment, associative tolerance was evident in the 72-hr and the 6-hr IDI conditions only. In the hot-plate assessment, associative tolerance was present in the 72-hr IDI condition only. The findings suggest that contextual tolerance to nicotine's analgesic effects are positively related to IDI length and are more readily demonstrated with the tail-flick method than with the hot-plate method. Overall, the results supported the thesis that nicotine tolerances that develop to different IDIs are qualitatively different and may be mediated by different psychological and physiological mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine Antagonists Do Not Block Conditioned Place Preference Induced by Paced Mating Behavior in Female Rats.

The authors assessed the behavioral effects of dopamine (DA) receptor antagonists, Cis (Z) flupentixol and S(+)-raclopride L-tartrate, on conditioned place preference (CPP) induced by paced mating behavior. Ovariectomized female rats of the Wistar strain were used. The administration of amphetamine (1 ior. mg/kg) induced a clear CPP that was completely blocked by the DA antagonists flupentixol (0.25 mg/kg) or raclopride (0.125 mg/kg). These doses had no effect on motor coordination. Female rats that mated in a pacing chamber developed a clear CPP. Neither flupentixol nor raclopride blocked the reward state induced by paced mating behavior. These results indicate that DA is not involved in the reward state induced by paced mating behavior in female rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The state of the reward comparison hypothesis: Theoretical comment on Huang and Hsiao (2008).

Rats avoid intake of a gustatory cue following pairings with a drug of abuse, such as morphine or cocaine. Despite the well-established rewarding properties of these drugs, the reduction in intake of the taste cue has been interpreted as a conditioned taste aversion for decades. In 1997, I proposed the reward comparison hypothesis suggesting that rats avoided intake of the drug-associated taste cue because the value of the taste cue pales in comparison to the highly rewarding drug of abuse expected in the near future. In this issue of Behavioral Neuroscience, A. C. W. Huang and S. Hsiao (see record 2008-17011-002) challenge the reward comparison hypothesis by showing parallels between amphetamine and LiCl-induced suppression of CS intake. This commentary addresses the current state of the reward comparison hypothesis in the context of the experiments completed by Huang and Hsiao and their new task-dependent drug effects hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preference for copying unambiguous demonstrations in dogs (Canis familiaris).

In an earlier study (P. Pongrácz et al., 2001), it was shown that human demonstration significantly enhances the detouring ability of dogs (Canis familiaris) around a V-shaped fence. The authors investigated the effect of the direction of the demonstrated detour and the dogs' detouring experience. They found that dogs' trial-and-error experience influences strongly the direction of the dogs' detours later, even if the demonstrator showed detours along the opposite side of the fence. However, dogs' preferences based on their own experiences were changed when the dogs observed demonstrations only on 1 side of the fence. Dogs with no trial-and-error experience followed the direction of 1-sided demonstrations. The change from dogs' own directions to the demonstrated directions seems not to be due to simple facilitative effects of social experience; the similarity with the demonstrated action depends on complex interactions between individual experience and socially provided information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of endothermy to huddling behavior in infant Norway rats ( Rattus norvegicus) and Syrian golden hamsters ( Mesocricetus auratus).

Infant Syrian golden hamsters (Mesocricefus auratus) do not exhibit endogenous heat production before 3 weeks of age and do not huddle effectively during cold exposure, gaining little thermoregulatory benefit from the presence of multiple littermates. In contrast, infant Norway rats (Rattus norvegicus) produce heat endogenously and are effective at maintaining elevated body temperatures by huddling. Therefore, the ineffective huddling of infant hamsters may be due to the absence of endogenous heat production. The huddling behavior of infants in mixed huddles of 8-day-old hamsters and weight-matched 4-5-day-old rats was observed to explore this possibility. The results indicate that hamsters, even when cold, effectively gain access to heat-producing rats, supporting the idea that endothermy contributes to the behavior of huddling by providing heat to each individual and thermal stimuli to other infants to support aggregation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)