Social influences on the selection of a protein-sufficient diet by Norway rats (Rattus norvegicus).

[Correction Notice: An erratum for this article was reported in Vol 104(2) of Journal of Comparative Psychology (see record 2008-10625-001). There was a misstatement. On page 137, second column, second paragraph, the sentence that begins on line 7 ought to read as follows: Protected t tests revealed that subjects in the Different Food-Same Place Group gained a significantly smaller percentage of body weight than did subjects in each of the other two groups (LSD = .67, both ps Rattus norvegicus) on selection of a nutritionally adequate diet by the naive. We found that during a 7-day test, isolated rats choosing among 4 foods, 3 of which were protein-deficient and 1 of which was protein-rich, failed to learn to prefer the protein-rich diet and lost weight. Conversely, those rats that interacted with conspecifics trained to eat the protein-rich diet developed a strong preference for that diet and thrived. The authors also found that Ss were more strongly influenced in their diet selection by the flavor of the foods eaten by conspecifics than by the locations where conspecifics fed. The results suggest that social influence may be important in development of adaptive patterns of diet choice by rats (or other dietary generalists) that need to find nutritionally adequate diets in demanding environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of caloric, protein, and sodium deprivation on the affiliative behavior of Norway rats (Rattus norvegicus).

The tendency of food-deprived, protein-deprived, and sodium-deprived Norway rats (Rattus norvegicus) and their respective controls to affiliate with conspecifics deprived of either food, protein, or sodium was examined. We found that (a) independent of internal state, focal rats offered a forced choice between protein-deprived and protein-replete target rats spent more time near replete than deprived target rats; and (b) both food-deprived and sodium-deprived focal rats offered a forced choice between food-deprived and replete target rats spent less time near fasted rats than did well-fed and sodium-replete focal rats. The data indicate that (a) rats can distinguish both food-deprived and protein deprived rats from replete rats and (b) the deprivation states of rats can affect their willingness to affiliate with deprived conspecifics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social identification of toxic diets by Norway rats (Rattus norvegicus).

48 naive female Long-Evans rats (observers) interacted with 2 conspecifics (demonstrators [n?=?96]) that had recently eaten a diet unfamiliar to the observer; ate 2 unfamiliar foods in succession, one of which was the food its demonstrators had eaten; suffered toxicosis; and were offered a simultaneous choice between the 2 diets they had eaten prior to toxicosis induction. During the choice test, observers exhibited an aversion to that diet their respective demonstrators had not eaten. It is suggested that exposure of a rat to conspecifics that have eaten a diet can act, as does actual ingestion of a diet, to reduce that diet's subsequent associability with toxicosis and that interaction with conspecifics may provide an alternative to individual trial-and-error learning in identification of toxic foods by rats that ingest a number of novel foods in succession before becoming ill. (12 ref) (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)     

The influence of preexperimental experience on social discrimination in rats (Rattus norvegicus).

The authors used laboratory rats (Rattus norvegicus) of known relatedness and contrasting familiarity to assess the potential effect of preexperimental social experience on subsequent social recognition. The authors used the habituation-discrimination technique, which assumes that multiple exposures to a social stimulus (e.g., soiled bedding) ensure a subject discriminates between the habituation stimulus and a novel stimulus when both are introduced simultaneously. The authors observed a strong discrimination if the subjects had different amounts of preexperimental experience with the donors of the 2 stimuli but a weak discrimination if the subjects had either equal amounts of preexperimental experience or no experience with the stimuli. Preexperimental social experience does, therefore, appear to influence decision making in subsequent social discriminations. Implications for recognition and memory research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal handling on playfulness by means of reversal of the desire to play in rats (Rattus norvegicus).

In the present study the authors sought to establish whether the range of effects of neonatal handling stimulation (H), that is, brief daily periods of infant isolation, could be extended to the domain of social motivation. With this aim, the authors studied the innate motivation to engage in rough-and-tumble play (R&T) in adolescent rats (Rattus norvegicus) by means of a reversal design, in which half of the rats were first housed in isolation (Days 1–3), and then in company (Days 4–6), while the other half followed the reverse sequence of housing conditions. Results showed in a clear-cut manner that H fuelled playfulness, as measured by pin and dorsal contact episodes, with (relative) independence of trait-based differences in fearful behavior between handled and nonhandled rats. Given that the different levels of the rat’s social brain are apparently sensitive to tactile stimulation in infancy, the authors propose that the vibrant R&T reported here could reflect an enduring alteration of genetically based, motivational systems underlying playfulness and, perhaps, positive social emotions like joy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of maternal responsiveness to Norway rat ( Rattus norvegicus) pup ultrasonic vocalizations.

Mother rats (Rattus norvegicus; 6 to 8 days postpartum) approach and maintain proximal orientation to a pup that is emitting ultrasonic vocalizations (USVs) far more than do virgin females (W. J. Farrell & J. R. Alberts, 2002). We used a playback regimen to examine the roles of acoustic and nonacoustic cues in regulating maternal proximal orientation toward vocalizing pups. When presented with recorded USVs, mothers of 6- to 8-day-old pups and nulliparous virgin females exhibited equivalent levels of proximal orientation toward the playback speaker. Mothers did show enhanced proximal orientation toward recorded USVs, however, if a silent pup was positioned below the speaker. Pup odors appear to be crucial for the maternal response to vocalizing pups, as peripherally induced anosmia attenuated maternal proximal orientation toward a vocalizing pup. Furthermore, spatial contiguity between olfactory and auditory stimuli was required for a maximal maternal response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of spatial food distribution on search behavior in rats (Rattus norvegicus).

To analyze how search strategies are adapted according to the geometric distribution of food sources, the authors submitted rats to a search task in which they had to explore 9 food trays in an open field and avoid visiting already-depleted trays. Trays were spatially arranged in 4 independent configurations: a cross, a 3 × 3 matrix, 3 clusters of 3 trays each, and a random configuration. Rats exhibited differential search efficiency as a specific effect of the susceptibility of the configurations to being explored in a principled way: Crosses were first, matrices or clusters were in the middle, and random configurations were last. Although no exhaustive searches or highly principled patterns were observed in any of the configurations, performances improved as the sessions went by. Thus, structural affordances of the environment influence the construction not only of search strategies but also of information linked to where the reward is. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Environmental influences on flank marking and urine marking by female and male rats (Rattus norvegicus).

Sprague-Dawley rats (Rattus norvegicus) were observed in a familiar environment. In Experiment 1, a leader entered a clean chamber, and an opposite-sex follower entered the chamber next. Both sexes began to flank mark after several sessions. Males flank marked more, and females locomoted more, but both sexes urine marked and investigated objects equally often. Leaders and followers did not differ on any measure. In Experiment 2, we measured floor marks more precisely and manipulated the number of objects and the presence of scent marks. Flank marking was more frequent in the presence of conspecific urine but did not vary with the number of objects or the sex of the rats. More objects elicited more investigating and urine marking and produced fewer floor marks but increased the number of marks in the central area in relation to the periphery. The results indicate that rats' flank marking is behaviorally distinct from urine marking and differentially affected by environmental variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social blockade of taste-aversion learning in Norway rats (Rattus norvegicus): Is it a social phenomenon?

In Experiment 1, hooded rats (Rattus norvegicus) were exposed to a novel diet in a food dish or on a conspecific; they were allowed to consume the same diet and then were injected with a toxin LiCl. Later both groups ate more of the novel diet than animals that had not been exposed, and the conspecific-exposed group ate more than the dish-exposed group. Reducing aversion learning by exposure on a conspecific is known as social blockade. We examined if this effect is because a conspecific intensifies dietary cues and thereby increases latent inhibition. Experiment 2 failed to show that diet on a conspecific is a more effective conditioned stimulus for taste-aversion learning than diet in a dish, and Experiment 3 showed that diet is an effective overshadowing stimulus in aversion learning but diet on a conspecific is not. These results suggest that social blockade cannot readily be assimilated to a latent-inhibition model and may be a distinctly social form of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal integration as a function of signal and gap intensity in rats (Rattus norvegicus) and pigeons (Columba livia).

Previous data suggest that rats (Rattus norvegicus) and pigeons (Columba livia) use different interval-timing strategies when a gap interrupts a to-be-timed signal: Rats stop timing during the gap, and pigeons reset their timing mechanism after the gap. To examine whether the response rule is controlled by an attentional mechanism dependent on the characteristics of the stimuli, the authors manipulated the intensity of the signal and gap when rats and pigeons timed in the gap procedure. Results suggest that both rats and pigeons stop timing during a nonsalient gap and reset timing after a salient gap. These results also suggest that both species use similar interval-timing mechanisms, influenced by nontemporal characteristics of the signal and gap. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grooming and yawning trace adjustment to unfamiliar environments in laboratory Sprague-Dawley rats ( Rattus norvegicus).

The authors studied grooming and yawning caused by mild stress in laboratory Sprague-Dawley rats (Rattus norvegicus). Two groups received 3 and 6 sequences of 5 foot shocks at random intervals (RI) and fixed intervals (FI), respectively. A 3rd group was not shocked (NS). The groups were exposed for 60 min twice. Grooming did not differ among groups, but yawning diminished with RI. Yawning increased and grooming decreased with the 2nd exposure, except in RI in which grooming increased. In NS and FI, grooming prevailed during the first 20 and 30 min, respectively, whereas yawning dominated the remainder of the time. In RI, grooming occurred more than yawning. An upward shift on this scale causes grooming to substitute yawning, whereas a downward shift causes the reverse effect. (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)     

Maternal responsiveness to infant Norway rat ( Rattus norvegicus) ultrasonic vocalizations during the maternal behavior cycle and after steroid and experiential induction regimens.

When removed from the nest and placed in a cool environment, Norway rat (Rattus norvegicus) pups emit ultrasonic vocalizations that can elicit maternal search behavior. The authors examined the behavior of pregnant dams, mothers, and virgin females during exposure to a pup that was either warm and silent or cool and vocalizing. Results indicate potentiated maternal reactions to a vocalizing pup: Mothers approached and maintained proximal orientation to a vocalizing pup far more than did virgin females. Elevated levels of proximal orientation appeared within hours of birth, increased during the 1st week postpartum, and declined by the time of weaning. Estrogen plus progesterone administration facilitated virgin females' proximal orientation toward vocalizing pups, whereas prolonged exposure to pups in the absence of hormones was without effect, suggesting that the ontogeny of the maternal response is regulated, at least in part, by maternal hormones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition of conspecific odors by laboratory rats ( Rattus norvegicus) does not show context specificity.

This experiment investigated how contextual cues affect recognition of conspecific odors in laboratory rats (Rattus norvegicus). Rats received 5 encounters with the same odor in the same context. For the 6th test encounter, all rats received a simultaneous presentation of the original odor and a novel odor. The authors tested 1 group of rats (context same) in the same context as before. For the remaining 2 groups, the test encounter was in a different context that 1 group (context different) had experienced but that 1 group (context novel) had not. A significant preference to investigate the novel odor by context-same and context-different rats, but not by context-novel rats, suggests that odor recognition can occur following transfer to a different, but familiar, test context, indicating a lack of context specificity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of sex, estrous cycle, and drug-onset age on cocaine self-administration in rats (Rattus norvegicus).

The influence of sex, phase of the estrous cycle, and age of drug onset on cocaine self-administration was examined. Adult male, adult female, and adolescent male rats (Rattus norvegicus) were evaluated using low fixed-ratio (FR) schedules of drug delivery with a single fixed cocaine unit dose or a range of cocaine unit doses with a single FR schedule. Sex differences in adults were observed for mg/kg consumption of the 3.0-mg/kg unit dose, with consumption being significantly less in estrus females than in males. Over the estrous cycle, mg/kg consumption of this unit dose was significantly less during estrus than during metestrus-diestrus. Differences due to age of drug onset were also observed, with mg/kg consumption of the 3.0-mg/kg unit dose being significantly less in adolescent males than adult males or adult females during metestrus-diestrus. In contrast, these various groups did not have significantly different mg/kg intakes of cocaine unit doses     

Differential effects of forward or simultaneous conditioned stimulus-unconditioned stimulus intervals on the defensive behavior system of the Norway rat (Rattus norvegicus).

To test several predictions derived from a behavior-systems approach, the authors assessed Pavlovian fear conditioning in rats after 30 trials of forward, simultaneous, or unpaired training. Direct evidence of conditioned fear was collected through observation of flight and freezing reactions during presentations of the conditioned stimulus (CS) alone. The authors also tested the CS's potential to reinforce an instrumental escape response in an escape-from-fear paradigm. On the one hand, rats that received forward training showed conditioned freezing, but no conditioned flight was observed. On the other hand, rats that received simultaneous training showed conditioned flight, but no conditioned freezing was observed. Rats that received either forward or simultaneous pairings showed instrumental learning of the escape-from-fear response. Implications for several theories of Pavlovian conditioning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats (Rattus norvegicus) encode the shape of an array of discrete objects.

To navigate efficiently, a traveler must establish a heading using a frame of reference. A large body of evidence has indicated that humans and a variety of nonhuman animals utilize the geometry, or shape, of enclosed spaces as a frame of reference to determine their heading. An important and yet unresolved question is whether shape information from arrays of discrete objects and enclosed environments are represented, and utilized, in the same way. In the present study, rats were presented with a reference memory task in which they had to find water that was hidden in 1 of 4 discrete and unique objects placed at the vertices of a rectangle. The results indicate that rats could utilize both feature and geometry cues to locate the hidden goal. The rats' performance declined during transformation tests using a triangular array, indicating that the rats may have encoded the primary axis of the object array, rather than local cues, to direct their search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anticipation of future events in squirrel monkeys (Saimiri sciureus) and rats (Rattus norvegicus): Tests of the Bischof-Kohler hypothesis.

The Bischof-Kohler hypothesis holds that nonhuman animals cannot anticipate a future event and take appropriate action when that event involves satisfaction of a need not currently experienced. Tests of the Bischof-Kohler hypothesis were performed with squirrel monkeys (Saimiri sciureus) and rats (Rattus norvegicus). In experimental trials with both species, a nonthirsty animal had its water bottle removed and then chose between a smaller and larger quantity of food. Consumption of the food induced thirst. Choice of the smaller quantity led to the return of the water bottle sooner than choice of the larger quantity. Monkeys reversed their baseline preference for the larger quantity of food when the experimental contingencies were introduced, but rats continued to prefer the larger amount. Although the rat findings support the Bischof-Kohler hypothesis, the monkey findings challenge it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultrasonic vocalizations of rats (Rattus norvegicus) during mating, play, and aggression: Behavioral concomitants, relationship to reward, and self-administration of playback..

Rats (Rattus norvegicus) emit a variety of ultrasonic vocalizations throughout their lifespan that reflect different forms of emotional arousal and accompanying affective states. In this study, high frequency recordings of ultrasonic vocalizations were made during mating, aggression, and both conspecific and heterospecific (dubbed "tickling") rough-and-tumble play behavior. We found that frequency modulated 50-kHz calls (trills and step calls) were positively correlated with positively valenced appetitive behavior during mating, play, and aggression. These calls were also positively correlated with the reward value of these social encounters. However, constant frequency (i.e., flat) 50-kHz calls were not related to appetitive behaviors or reward. In contrast, 22-kHz calls were positively related to aversive/withdrawal behaviors during mating, play, and aggression. Finally, we found that rats self-administered playback of frequency modulated 50-kHz trill calls and avoided playback of 22-kHz calls. Playback of flat 50-kHz calls or tape hiss was neutral. These results suggest that frequency modulated 50-kHz calls index a positively valenced, appetitive, social-emotional state in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)