Female presence during postejaculatory interval facilitates penile erection and 22-kHz vocalization in male rats.

During the postejaculatory interval (PEI), male rats exhibit prolonged immobility, 22-kHz vocalization, and penile erections. To test whether females modulate these behaviors, females were removed after the first or second ejaculation or left in the test chamber. Female presence during the PEI delayed exploratory behavior and facilitated vocalization and erection. Female stimulation of vocalization is consistent with the hypothesis that vocalization has a communicative function, not just a thermoregulatory one. The timing of the effect of females on erection suggests that males are sexually arousable well before they resume copulation. Therefore, erection may be better than vocalization as an indicator of the male's sexual refractoriness. The findings also challenge the conventional view that the PEI comprises absolute and relative sexual refractory periods marked, respectively, by the presence and absence of 22-kHz vocalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential rates of exhaustion and recovery of several parameters of male rat sexual behavior.

Studied sexual exhaustion of 12 sexually experienced Long-Evans male rats with respect to several copulatory measures. The ejaculatory latency, intercouplatory interval, and intromission frequency demonstrated a U-shaped curve, exhibiting high values for the initial ejaculatory series, falling to a minimum at an intermediate ejaculatory series, and again increasing at exhaustion. The absolute refractory period of the postejaculatory interval (measured at vocalization termination) increased linearly, whereas the relative refractory period (the remaining portion of the postejaculatory interval) was a positively accelerating function. Partial recovery tests demonstrate that the preejaculatory measures and absolute refractory period substantially returned to baseline values by Day 6, while the relative refractory period was still extended. The significance of these data to the theoretical modeling of sexual behavior is discussed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation between 22-kHz ultrasonic signals and sociosexual behavior in rats.

The copulatory performance of male rats, tested in a large seminaturalistic environment, was assessed to determine the relation between 22-kHz ultrasonic vocalizations and a range of sociosexual behaviors. The 7 sexually experienced Charles River male rats were tested until sexual exhaustion. Ultrasonic signals were shown to occur in a wider range of sociosexual circumstances than previously reported; for example, the calls occurred in particular social circumstances during the preejaculatory period as well as during the postejaculatory interval. There was no consistent evidence that the emission of this call during the postejaculatory period consistently functions to keep the female away from the male. The nature and occurrence of postejaculatory ultrasonic signals showed increasing variability in successive ejaculatory series. The results of this and previous studies are interpreted within a semiotic theory of communication. The 22-kHz call is described as a message that makes available the information that the sender is in a socially depressed and withdrawn state. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emergence of displacement activities in the male rat following thwarting of sexual behavior.

Conducted 7 experiments with Wistar rats, who were observed in a mating area equipped with a water spout, that revealed the emergence of displacement drinking and hindlimb scratching in noncopulating castrated males and in males with medial preoptic (MPO) lesions exposed to sexually attractive stimulus females. By contrast, sexually quiescent males in the postejaculatory refractory period showed no evidence of displacement activity, and anestrous females displayed only moderate increments in drinking and scratching, compared with copulating estrous females. In both castrated and MPO-lesioned males, the amount of displacement activity was inversely related to strength of masculine sexual behavior, and in castrated Ss, displacement behavior was suppressed by the subcutaneous implantation of a testosterone-filled capsule. When no stimulus females were present, no difference in drinking and scratching by control, castrated, and MPO-lesioned Ss was discerned. Sexually inactive females elicited less displacement activity in castrated Ss than did females in estrus. However, unreceptive stimulus females frequently elicited displacement behaviors in normal sexually active males. Findings are discussed in relation to current concepts of psychological organization of masculine sexual behavior. It is suggested that the emergence of displacement behavior in castrated, MPO-lesioned, and normal males paired with anestrous females may be due to the thwarting of sexual motivation. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postejaculatory quiescence in female and male rats: Consequences for sperm transport during group mating.

Studied the pattern of postejaculatory mating in the social context of a multimale–multifemale group of Sprague-Dawley rats (N?=?21), analyzing its timing and sequence from the females' as well as the males' perspective. During mating, females had a quiescent period following each ejaculation, which was comparable with the males' (a postejaculatory interval, PEI). The PEIs of both sexes were characterized by 3 behaviorally distinguishable phases: a stationary, an interactive, and a sexual phase. There was no significant sex difference in the total length of the PEI. Nonetheless, females began active sexual behavior and entered the sexual phase more quickly than males. The time course of each phase of the PEI is compared with the time course of sperm transport in the female, and the similarities and differences between the two sexes' reproductive strategies following an ejaculation are emphasized. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in behavioral responses to a competitive mating situation in two species of dwarf hamster (Phodopus campbelli and P. sungorus).

Social groups consisting of a female and two adult males, of two closely related species, Phodopus campbelli and P. sungorus, were observed during a 2-hr mating test. The behavioral analysis revealed (a) significant differences between the two species in the ability of the dominant male to exclude the subordinate male from mating with the estrous female and (b) significant changes in the pattern of copulation by the dominant male in response to the presence of a second male even when the second male was not mating with the female. Dominant male P. sungorus were always successful in preventing subordinate males from mating. In contrast, subordinate male P. campbelli mated with the female in 6 of 12 groups in spite of high levels of aggression and the potential for serious injury. When both P. campbelli males mated, dominant males ejaculated first and most frequently. The response to the presence of a second male in P. sungorus included an accelerated copulatory pattern, with decreased durations of individual ejaculatory series and postejaculatory refractory periods. This resulted in an average of one extra ejaculation during the first hour of testing. The temporal pattern of mating in P. campbelli was not accelerated by the presence of a second male, but the intromission/mount ratio was increased significantly, and the duration of the ejaculatory lock decreased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysiological and ultrasonic correlates of reproductive behavior in the male rat.

Monitored the ultrasonic vocalizations of 13 male Long-Evans rats and determined the correlation of these vocalizations with electrophysiological activity measured by chronically implanted hippocampal and cortical electrodes during mating with a female rat. Hippocampal theta rhythms were significantly correlated with high activity, mounting, intromissions, and preejaculatory excitatory behavior and were also significantly associated with 50-kHz short ultrasonic vocalizations. Postmount or postintromission behaviors (grooming, exploration) were closely correlated with an absence of ultrasonic vocalizations and the onset of irregular low-amplitude hippocampal EEG recordings. Long 22-kHz vocalizations occurred during the postejaculatory refractory period. Shorter 22-kHz vocalizations occurred during mating and were associated with unsuccessful intromissions or mounting attempts. Postejaculatory long 22-kHz vocalizations were significantly associated with irregular high-amplitude hippocampal EEG tracings, while preejaculatory short 22-kHz vocalizations were also accompanied by sleeplike irregular high-amplitude hippocampal EEG tracings with cortical spindling. Findings suggest that ultrasonic vocalizations are indicators of the sexual arousal of mating rats. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual arousal in male pigtailed monkeys (Macaca nemestrina): Effects of serial matings by two males.

Examined male sexual arousal in 4 vasectomized male and 3 intact multiparous female pigtailed monkeys with the postejaculatory interval (PEI) used as the dependent variable. 12 paired trials were conducted in which a male and female copulated, the 1st male was removed and a 2nd male was or was not allowed to copulate with the female, and the 1st male was again permitted to copulate with the female. In male–female pairs, the PEI was shortened by 60% of normal (control) values if the male observed another male copulating with his female partner. Results demonstrate that the normal PEI is not an absolute male refractory period; males are capable of copulating sooner, and they will do so when presented with certain behavioral stimuli. A long PEI may prevent males from disrupting their own plugs prematurely, whereas a short PEI may result from a premature disruption of the plug by another male. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social memory of the male laboratory rat.

Used duration of social-investigatory behavior by 36 mature male Long-Evans rats as a measure of individual recognition in 5 experiments to assess social memory. In Exp I, the duration of social investigation during a 2nd exposure to the same juvenile (n?=?12) was directly related to the length of the interexposure interval. In Exp II, Ss were exposed to the same or different juvenile 10 min after an initial 5-min exposure to a novel juvenile; reexposure to the same juvenile elicited significantly less social investigation than an exposure to a different juvenile. Exps III and IV demonstrated that following a 5-min introductory exposure, social memory of the juvenile was relatively brief in comparison with that of mature Ss. Exp V revealed a retroactive interference effect on recently acquired memory for an individual: 12 mature Ss exposed to interpolated social experience engaged in significantly longer investigation of a juvenile than those with no interpolated social experience. The combined results suggest that (1) the rat normally engages in spontaneous learning of individual identity and (2) social memory may be a significant aspect of complex social interactions. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

One-trial associative memory in black-capped chickadees.

Black-capped chickadees (Parus atricapillus), birds that store food, inspected feeders in an aviary (1 of which was baited) and returned after a 5-min retention interval to consume the then-hidden food. In Exp 1, Ss quickly learned this task but only if different feeders were used on each trial. In Exp 2, memory for the baited feeder decayed substantially after 24 hrs but not after 30 min. In Exps 3 and 4, there were 4 alternatives to the baited feeder. Ss performed better than chance from the beginning of these experiments. When Ss made errors on their 1st choice, Ss performed better than chance on their 2nd choice. Exp 4 tested the notion that increasing the cost of inspecting the feeders would reduce errors; however, this did not improve performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intertrial reinstatement of training stimuli on complex maze learning in rats: Evidence that "acquisition" curves reflect more than acquisition.

In Exps I–III (224 male Sprague-Dawley rats), Ss were run in a complex maze to escape weak footshock or to approach an appetitive reinforcer. Extramaze intertrial reinstatement of the same reinforcer as that used in training was found to enhance subsequent maze performance. Exp IV (80 Ss) determined that appetitively and aversively motivated performance benefitted from brief intertrial exposures to the start box of the maze. In Exp V (64 Ss), a facilitatory effect indicated that memory trace activity need not be maintained between training and reinstatement or between reinstatement and subsequent training. Exp VI (80 Ss) examined the effects of reinstatement at the beginning, middle, or end of 5-min intertrial intervals and found enhanced performance in the last 2 conditions. Exp VII (24 Ss) established that 4 successive reinstatement treatments without interpolated training trials were no more beneficial than a single reinstatement. Exp VIII (16 Ss) determined that forgetting had occurred over the standard 5-min interval between training trials. Exp IX (32 Ss) found that reinstatement alleviated forgetting that had already transpired. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of physostigmine upon consolidation of memory in mice.

Investigated the influence of physostigmine upon the consolidation process in 4 experiments with 162 male DBA/2J mice. Ss were trained to escape shock in a 'Y'-maze. In Exp I physostigmine (.4 mg/kg, ip) impaired a previously learned task 2 days after initial learning but improved performance 11 days after initial learning. In Exps II and III, it was determined that the impairment of memory found on Day 3 was transitory and no longer evident once the drug was no longer active in an S's system. The findings of Exp IV, in which the Day 12 facilitory effect was examined, were essentially the same as those of Exps II and III. Results tend to support an inhibitory or motivational hypothesis rather than a consolidation hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear conditioned with escapable and inescapable shock: Effects of a feedback stimulus.

Four experiments, with 140 male Fischer rats, compared the level of fear conditioned with escapable and inescapable shock. In Exps I and II, master Ss that had received 50 unsignaled escapable shocks were less afraid of the situation where the shock had occurred than were yoked Ss that had received inescapable shocks. Comparable results were found in Exps III and IV, which used freezing as an index of fear of a discrete CS that had been paired with shock. Control per se was not necessary to produce the low level of fear seen in the master Ss. Yoked groups receiving a feedback signal at the time the master made an escape response showed a low level of fear that was comparable to that of the masters and significantly less than that seen in the yoked Ss without feedback. In addition, there were strong suggestions that control and feedback exert their effects through the same or highly similar mechanisms. Possible explanations for how control and the exteroceptive feedback signal produce this effect are discussed. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paternal stimulation during infancy: Effects upon aggression and open-field performance of mice.

Studied aggression in random-bred albino Tuck TT strain male mice from 1st matings, reared by both parents (n = 13) and from 2nd matings, reared only by the mother (n = 15). Prolonged isolation from weaning induced more aggression in Ss from 1st matings than in Ss from a 2nd mating. In a 2nd experiment, fathers of 40 Ss were removed (a) shortly after mating, (b) at the litters' birth, or (c) at weaning. In offspring isolated from weaning, Ss in condition c were significantly more aggressive than those in a, while those in b showed an intermediate response. These differences did not occur when the period of isolation was broken by 50 days of communal housing before aggression testing, although Ss in c defecated more in the open field. It is suggested that young mice "imprint" toward the same odors of adult males which in later life elicit intermale aggression. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

To know oneself is to like oneself: Self-certainty and self-affect.

Four experiments demonstrated that certainty about self-attributes is associated with positive affect about the self. In Experiments (Exps.) 1–3, low esteem was associated with less certainty about possessing several trait attributes, as measured by confidence intervals (Exps. 1–2) and reaction time (Exp. 3). The finding that low-esteem Ss were less certain was reversed when Ss rated the traits in public (Exp. 2a), suggesting that low-esteem Ss do not simply respond to impression management cues, and was attenuated when Ss estimated the traits of friends (Exps. 2b and 3), suggesting that lack of certainty of low-esteem people is specific to self-judgments. In Exp. 4, Ss exposed to certain diagnoses of their self-perceived traits showed an improvement in self-affect and egotism. Links between prediction and control, and subsequent affect about the self are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus and response contingencies in the misbehavior of rats.

Misbehavior by rats was produced in Exps I (16 Wistar female albino rats) and II (15 Sprague-Dawley female albino rats) by pairing a ball bearing with food or by requiring contact with the ball bearing for food (Exps IV, 6 Ss, and V, 11 Ss). Misbehavior occurred before and after eating the food pellet. The frequency, complexity, and duration of prepellet misbehavior was increased by delay of food until after the ball bearing exited (or was programmed to exit) and by requiring contact with the bearing to obtain food. Alternative goal-directed behaviors occurred in Pavlovian contingencies in which food was delivered before the bearing was programmed to exit. Postpellet misbehavior tended to occur when food was delivered before the bearing was programmed to exit and before S released the bearing. Omission of food delivery on contact reduced the duration, complexity, and frequency of misbehavior, although experienced Ss continued to contact (Exp III, 15 Ss). Misbehavior was affected by both stimulus- and response-reward contingencies but showed characteristic organization and topography under both types of contingency. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition and extended retention of a conditioned taste aversion in preweanling rats.

Four experiments employed a taste aversion conditioning procedure appropriate for both neonatal and adult rats to investigate the ontogeny of extended retention. In Exp I, 200 outbred albino rats trained at 1, 10, 20, or 60 days of age were tested for retention of the taste aversion 25 days later. At testing, only those Ss conditioned when 20 or 60 days old demonstrated significant taste aversions. Exps II and III, with 190 Ss, established that Ss 14–25 days old and older were able to retain significant taste aversions following a 25-day retention interval. 80 younger Ss did, however, acquire and retain the aversion for several days and showed a gradual retention loss over progressively longer retention intervals (Exp IV). Findings suggest that preweanling rats demonstrate initial consolidation, storage, and retrieval of conditioned taste aversions. It is only after this initial period that retention deficits become evident. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Copulatory behavior of roof rats (Rattus rattus).

Investigated the copulatory behavior of a total of 71 male and 48 female roof rats (Rattus rattus) in 3 experiments. In Exp I, females were brought into behavioral estrus with exogenous hormones, and each pair was observed until 30 min elapsed without copulation. Roof rats appeared to be similar to laboratory rats (Rattus norvegicus) with regard to basic motor patterns of copulation, quantitative measures of copulation, behaviors accompanying copulation, and postejaculatory ultrasonic vocalizations. Only (a) patterns of tail rattling in females, (b) climbing and allogrooming in both sexes, and (c) an ability to ejaculate on a single insertion by males were observed in roof rats but not reported for laboratory rats. Exps II and III were designed to assess the role of various components of the copulatory pattern of male roof rats on the induction of pregnancy in normally cycling young females. A single ejaculation preceded by an abnormally high number of intromissions or 3 normal ejaculatory series maximized the incidence of pregnancy, whereas 1 normal ejaculatory series or 1 ejaculation preceded by an abnormally low number of intromissions did not. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binocular vision and spatial perception on 4- and 5-month-old infants.

Conducted 4 experiments investigating the relation between the development of binocular vision and infant spatial perception. Exps I and II compared monocular depth perception in 39 4- and 5-mo-old infants. Results show that Ss in both age groups reached more consistently for the nearer of 2 objects under binocular viewing conditions than under monocular viewing conditions. Exps III and IV investigated whether the superiority of binocular depth perception in 89 4-mo-olds is related to the development of sensitivity to binocular disparity. In Exps I–II, under binocular viewing conditions, Ss who were identified as disparity-sensitive reached more consistently for the nearer object than did Ss who were identified as disparity-insensitive. The 2 group's performances did not differ under monocular viewing conditions. Results suggest that, binocularly, the disparity-sensitive Ss perceived the objects' distances more accurately than did the disparity-insensistive Ss. In Exps II–IV when Ss were habituated to an object, then presented with the same object and a novel object that differed only in size, disparity-sensitive Ss showed size constancy by recovering from habituation when viewing the novel object. Disparity-insensitive Ss did not show clear evidence of size constancy. Findings suggest that the development of sensitivity to binocular disparity is accompanied by a substantial increase in the accuracy of infant spatial perception. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning insulin effects.

It has previously been demonstrated that after a number of insulin injections in rats, an injection of a placebo leads to an elevation in blood sugar. It has been suggested that this apparent conditioned compensatory response is an artifact resulting from stressing the S (when large doses of insulin are used) or represents a nonassociative phenomenon (when small doses of insulin are used). 4 experiments are reported, using a total of 63 male Wistar rats as Ss. These 2 suggestions were rejected on the basis of results of Exps I and II. Exps III and IV demonstrated that although the behavioral effects of insulin can be conditioned to the injection procedure, such conditioned insulinlike behaviors (contrary to suggestions of many investigators) are not mediated by a hypoglycemic state. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)