Lactose ingestion in the adult golden hamster (Mesocricetus auratus)

Adult mammals generally demonstrate a lower preference for the disaccharide sugar lactose than for any other common sugar, and because adults typically have low levels of the intestinal enzyme lactase, lactose ingestion may cause gastrointestinal distress. The lactose intake of adult golden hamsters was examined in three experiments; the main findings were: (a) hamsters allowed to choose between tap water and lactose solutions (maximum concentration = 32% weight/volume) over a 20-day period showed a clear preference for lactose solutions and ingested substantial quantities of lactose (up to 3 g/100 g body weight/day) without noticeable adverse effects; (b) hamsters consuming a single diet with lactose added (maximum concentration = 50%) over a period of days ingested up to 3.42 g/100 g body weight/day of lactose without noticeable adverse effects; (c) both hamsters with prior exposure to lactose solutions and those without such exposure consumed similar amounts of 32% lactose solution over an 8-day period, suggesting that hamsters' lactose intake does not depend on the occurrence of adaptation. It is suggested that the fermentative capacity of the hamster's pregastric pouch may underlie this animal's unusual tolerance for lactose.     

Sex differences in coincidence-anticipation timing (CAT): a review

Coincidence-anticipation timing (CAT) is the ability to judge when a moving stimulus will arrive at a target. 43 articles were reviewed which investigated sex differences in this skill. Performance was typically recorded as one or more of three error measures, absolute error (AE), constant error (CE), and variable error (VE). Despite many null findings, it is argued that the evidence for a male advantage is strong, particularly for AE and VE. 10 parameters typically associated with CAT studies were analyzed (e.g., knowledge of results, number of trials, stimulus duration, and stimulus speed), but none differentiated clearly between the presence and absence of the sex difference. However, when the mean AE score was used as a measure of task difficulty, a male advantage was reliably associated with lower values of AE (easier tasks) and null findings with higher values (more difficult tasks). An attempt to compare sex difference findings from Bassin timer and real-world tasks was thwarted by the lack of studies using real-world tasks. Given little evidence for the influence of socialization on sex differences in CAT, it is suggested that the difference may have originated from the evolutionary selection of women for gathering and men for hunting.     

Determinants of mating success in the golden hamster (Mesocricetus auratus): I. Male capacity

Rested adult golden hamsters produced a mean of 13 ejaculations and then showed a modified copulatory pattern consisting of long intromissions (10-30 s of intravaginal thrusting) during which no sperm transfer occurs. When a second (fresh) female was introduced, 58% of the males produced at least one more ejaculation, and 17% of the males produced one further ejaculation when placed with a third female. In similar three-female tests conducted 24 hr later, all males ejaculated (M = 4 ejaculations); this level of ejaculatory output was maintained over a subsequent 10-day period of daily testing. Four ejaculations ensured a nearly 100% pregnancy rate and maximum litter size in the first females. Second and third females, however, received fewer ejaculations and subsequently showed reduced fertility and produced smaller litters. Most males showed high levels of long intromissions on all days and with all females. The physiological significance of these long intromissions may be to trigger the progestational response. Examination of the rate of recovery from sexual exhaustion indicated that 2 or 8 hr of rest resulted in fewer than 50% of the males being capable of one further ejaculation. However, most of these single ejaculations were accompanied by long intromissions and resulted in successful pregnancies. Four to eight days were required for full recovery of ejaculatory capacity. This study showed that the male golden hamster has a higher ejaculatory output and more rapid recovery from sexual exhaustion than other small rodents that have been studied. Thus, the limits of male capacity appear to vary widely among species.     

Receiver operating characteristics (ROCs) in recognition memory: a review

Receiver operating characteristic (ROC) analysis is being used increasingly to examine the memory processes underlying recognition memory. The authors discuss the methodological issues involved in conducting and analyzing ROC results, describe the various models that have been developed to account for these results, review the behavioral empirical literature, and assess the models in light of those results. The empirical literature includes studies of item recognition, relational recognition (e.g., source and associative tests), as well as exclusion and remember-know tasks. Nine empirical regularities are described, and a number of unresolved empirical issues are identified. The results indicate that several common classes of recognition models, such as pure threshold and pure signal detection models, are inadequate to account for recognition memory, whereas several hybrid models that incorporate a signal detection-based process and a threshold recollection or attention process are in better agreement with the results. The results indicate that there are at least 2 functionally distinct component/processes underlying recognition memory. In addition, the ROC results have various implications for how recognition memory performance should be measured.     

Ontogeny of agonistic behaviour in dispersing blind mole rats (spalax ehrenbergi)

The blind mole rat (Spalax ehrenbergi) is a solitary and aggressive fossorial rodent that inhabits its own individual tunnel system. Mole rats breed mainly in the winter, giving birth to a litter of three to four young on average [Nevo (1961) Mammalia 25:127–143]. Intraspecific interactions between adults occur mostly during the winter, which is the rainy season in Israel; after parturition, interactions occur between the mother and her offspring and between the siblings themselves until dispersal. Until now, the subterranean habitat of mole rats has prevented direct observation in the wild. Thus, there has been no direct evidence for the proximal factors that drive juvenile mole rats out of the maternal tunnel system as they shift from the social life-style of the young to the solitary life-style of the adult. In the present study, female mole rats were caught in the wild with their offspring and brought to the laboratory. The dispersal process of the young from the maternal nest was followed under two housing conditions: (1) restricted housing, simulating the physical conditions under which dispersal is delayed past the usual age, as often occurs during late winter floods in the field in areas of nonporous clay soils, and (2) nonrestricted housing, simulating the physical conditions that allow the young to disperse from their maternal tunnels at any time. In each housing condition, the mothers raised either one or three pups. During pup development, we monitored both maternal and juvenile agonistic variables during intraspecific interactions. Five major behavioural phases were identified during the ontogeny of the mole rat pups. Maternal aggression toward pups increased mainly in the first three phases of pup development, and sibling aggression increased from the third phase until dispersal. Under the restricted housing conditions, there was a delay in both the appearance of aggression in the “family group” as well as in dispersal age compared with the nonrestricted conditions. In the nonrestricted conditions, increased litter size resulted in delay in dispersal age. We suggest that the main proximate factor initiating natal dispersal is increased intolerance and aggression among siblings rather than maternal aggression. Only after the young began dispersing from the maternal tunnels did maternal aggression dramatically increase, thus preventing the offspring from returning. However, following floods, inhibition of aggression may enable the mole rat pups to stay with the family group and to disperse later when the physical conditions permit it. Aggr. Behav. 24:455–470, 1998. © 1998 Wiley-Liss, Inc.     

The Millon Clinical Multiaxial Inventory (MCMI): a review

This article reviews research conducted to date on the Millon Clinical Multiaxial Inventory (MCMI), a self-report test of psychopathology. The composition of the test and its theoretical basis are described. Data regarding its internal psychometric structure are reviewed. Finally, the article summarizes the research on the validity of the MCMI.     

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.     

The efficacy of cognitive-behavioral interventions for reducing anxiety sensitivity: a meta-analytic review

The present study meta-analytically reviewed the efficacy of cognitive-behavioral therapy (CBT) vs. control conditions in the reduction of anxiety sensitivity. A computerized search was conducted to indentify CBT outcome studies that included the Anxiety Sensitivity Index as a dependent variable. Of the 989 studies that were identified, 24 randomized-controlled trials with a total of 1851 participants met inclusion criteria and were included in the analysis. Data were extracted separately for treatment-seeking (16 studies) and at-risk (eight studies) samples. Results indicated large effect sizes for treatment-seeking samples, Hedges' g=1.40, SE=0.21, 95% CI: 1.00-1.81, p<0.001, and moderate to large effect sizes for at risk samples Hedges' g=0.74, SE=0.18, 95% CI: 0.39-1.08, p<0.001. Additionally, both the amount of therapist contact and control modality (waitlist vs. psychological control) moderated the effect sizes for treatment-seeking samples. Our review indicates that CBT is efficacious in reducing anxiety sensitivity. However, more research is needed to determine the mechanisms by which CBT exert its effects on anxiety sensitivity.     

Human sensitivity to reinforcement: A comment on Kollins, Newland, and Critchfield's (1997) quantitative literature review

In a quantitative review of human operant experiments, Kollins, Newland, and Critchfield (1997) found that humans are less sensitive to reinforcement contingencies than nonhumans are. Human performances were not as consistent with the matching law, and they were more variable from subject to subject. Some of the variables correlated with reduced human sensitivity were surprising. These included collection of the data under more controlled conditions (laboratory rather than naturalistic settings), and inclusions of discriminative stimuli correlated with alternative sources of reinforcement. We discuss these unexpected findings in the light of criticisms that have been leveled against meta-analytic literature reviews (e.g., the wisdom of grouping studies with widely diverse methods), and we suggest ways of improving future analyses of the behavior-analytic literature.     

Food hoarding behaviour in the golden hamster (Mesocricetus auratus): Effects of body weight loss and hoard-size discrimination

Two experiments investigated some of the factors that influence food hoarding behaviour in the golden hamster (Mesocricetus auratus). In Experiment 1, hamsters given limited access to food failed to increase the amount of food they consumed at each meal. Instead, they exhibited a significant increase in the amount of food taken to hoard during the limited access period, and this permitted hamsters who were allowed to retain their hoard to maintain body weight at levels comparable to free-feeding controls. Hamsters that were not allowed to retain hoarded food rapidly lost body weight. There was also an inverse correlation between body weight and amount of food taken to hoard in all hamsters given limited access to food, suggesting that body weight loss was one factor directly related to increased hoarding during periods of limited food accessibility. Experiment 2 investigated the effect of hoard-size discrimination on food hoarding in hamsters by artificially manipulating hoard size. The results suggested that hoarding behaviour could be influenced by artificially depleting and repleting the hoard, and this factor appears to influence hoarding in the absence of any significant changes in body weight. These results are discussed in relation to the kinds of adaptive feeding strategies that hamsters may utilize in their natural environment.     

Individuality in coo calls of adult male golden snub-nosed monkeys (Rhinopithecus roxellana) living in a multilevel society

Animal Cognition - Vocal individuality is a prerequisite for individual recognition, especially when visual and chemical cues are not available or effective. Vocalizations encoding information of...     

Effects of toxicosis on the predatory behavior of the golden hamster (Mesocricetus auratus)

The purpose of this study was to measure the effects that toxicosis had on the hamster's predatory behavior and to compare these results with those found in previous studies with grasshopper mice. A 0.15 M LiCl injection caused hamsters to develop a greater aversion and to inhibit their feeding and attack responses more frequently toward a house cricket than did a similar injection of NaCl. The added presence of an almond coating on the cricket prolonged the number of days that a hamster exhibited an aversion toward the prey and an inhibition to attack. Essentially, the inhibitory effects from toxicosis in the hamster paralleled those found with the grasshopper mouse. The differences in these inhibitory effects are attributed to inherent differences in the attack responses of the two rodents.     

Intrasexual interactions among female golden hamsters (Mesocricetus auratus) over the estrous cycle

Social interactions of cycling female golden hamsters paired with ovariectomized animals in large enclosures were primarily agonistic over the 4-day estrous cycle. These aggressive interactions were intense as indicated by frequent occurrences of chase and flight behavior. Dominant and subordinate social ranks were established in the majority of pairs (96%) tested, and even females in sexual heat were capable of attacking and dominating their rivals. Furthermore, cycling females exhibited significantly more aggressive acts than ovariectomized opponents 1 day prior to sexual receptivity. No differences in fighting patterns were found between animals on the other 3 days of the estrous cycle. Additional analyses revealed clear differences in agonistic elements, including flank marking, between dominant and subordinate females regardless of whether they were gonadectomized or intact. These analyses also showed that dominant individuals frequently chased and bit opponents during encounters within their nesting area. The data are examined for implications on the adaptive organization of female hamster agonistic behavior and the neuroendocrine regulation of species-typical behavior over the estrous cycle.