Experiments on neophobia in wild and laboratory rats: A reevaluation.

Reports 2 experiments using food-container avoidance as an index of neophobia in a total of 20 adult male wild rats and 20 domestic Long-Evans and 20 Wistar rats. In Exp I Ss were fed from a single familiar container until their consumption had stabilized. Upon replacing the familiar container with a novel container, the latency of all 3 strains to begin feeding increased. In Exp II, Ss were offered a choice between a familiar and a novel container containing identical food. Though there was considerable individual variation among the 3 strains, the wild strain was more reluctant to eat from the novel container than the Long-Evans (hooded) Ss, which, in turn, were more reluctant than the Wistar (albino) Ss. Nonetheless, all 3 strains showed an initial avoidance of the novel container. It is concluded that both wild and laboratory strains are neophobic and that strain differences are ones of degree, not of kind. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Free-operant comparisons of wild and domestic Norway rats.

Compared 16 wild and 16 domestic hooded rats on nondifferential appetitive VI responding, discrimination, and discrimination reversal procedures. The effects of strain, sex, deprivation, preexperimental handling, and sessions on response rate were examined. Performances during the 60 days of VI training showed prolonged increases over that period for all strain-sex groupings, with domestic Ss responding at higher rates than wild. Males also tended to respond at higher rates than females. During the discrimination procedure wild Ss showed more resistance to extinction, although these differences generally diminished after the 30 days of training. During the discrimination reversal procedure domestic Ss reversed their responding pattern more readily, and domestic females reached criterion significantly sooner than domestic males. The effects of deprivation and handling were not significant during the experimental procedures.(20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of domestication on production and perception of mallard maternal alarm calls: Developmental lag in behavioral arousal.

Conducted field and laboratory studies to assess the effects of intense genetic selection on the production and perception of the maternal alarm calls of 150 domestic (Peking) and 120 wild mallard ducks (Anas platyrhynchos). With respect to production, the calls of wild and domestic Ss were comparable on 4 acoustic features and differed only slightly on 2 features. With respect to perception, the calls of wild and domestic hens were equally effective in promoting behavioral inhibition in wild and domestic ducklings. Although data reveal little or no effect of domestication on maternal alarm call, an unexpected effect was found regarding the domestic ducklings' behavior. Peking Ss showed a greater level of behavioral inhibition than mallards at 24 hrs of age. Further experiments indicated that the differential level of inhibition in the wild and domestic birds reflects a developmental lag in arousal consequent to domestication: 72-hr-old Peking ducklings were behaviorally more aroused than 24-hr-old Peking ducklings and were similar to 24-hr-old mallard ducklings in that respect. This appears to be the first demonstration of behavioral heterochrony, which is believed to be an important mechanism of behavioral evolution. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Species-specific danger signals, endogenous opioid analgesia, and defensive behavior.

Examined the effects of handling stimuli and stress odors on species-specific defensive behavior and pain sensitivity with a total of 100 female Sprague-Dawley derived rats in 4 experiments. Ss not adapted to handling had longer jump latencies on the hotplate test of pain sensitivity than those with extensive handling experience. In a postshock freezing test in Exp II, naltrexone (7 mg/kg, intraperitoneally) enhanced defensive freezing relative to saline controls in nonadapted Ss. However, naltrexone produced no such effect in Ss that were adapted to handling. These 2 studies indicate that the handling procedure triggered an endogenous opioid analgesic response in Ss not adapted to handling. Exp III showed that a similar naltrexone-reversible opioid analgesia could be triggered by stress odors. Naltrexone, when compared to saline, enhanced postshock freezing in the presence of conspecific stress odors but not in their absence. In Exp IV, stress odors and nonadapted handling were able to activate defensive freezing directly when tested in compound but not in isolation. Results are consistent with the view that stress odors and handling stimuli are danger signals that activate endogenous opioid analgesia as well as defensive behavior, suggesting that analgesia is a component of the rat's defensive behavior system. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relatively brief environmental enrichment aids recovery of learning capacity and alters brain measures after postweaning brain lesions in rats.

Two experiments showed that enriched postlesion experience aided in overcoming effects of simultaneous bilateral cerebral lesions made at 30 days of age in 64 male inbred Fischer rats (Exp I) and 60 male Berkeley S-sub-1 rats (Exp II). The lesions were directed to the occipital cortex, but in most cases there was also some impairment of the hippocampus. For 60 days after operations, half of the Ss lived in small individual cages and half lived in groups in large enriched-environment cages. They were then pretrained and tested on the standard 12 Hebb-Williams problems. Daily injections of methamphetamine (vs saline) during the period of differential experience in Exp I had no effect on the behavioral scores. Exp II included groups that received only 2 hrs/day of enriched experience, and they benefited as much as groups that remained in the enriched environment 24 hrs/day. Results demonstrate significant beneficial effects of environment when bilateral lesions were made at a later age and when the periods of enriched experience were shorter than have previously been tested. Two additional experiments with 112 Berkeley S-sub-1 rats revealed significant effects of both lesions and environment on weight and RNA/DNA of brain regions. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Domestication, sophistication, and avoidance in Norway rats.

Administered successive 1-way and 2-way avoidance tasks which included treatments of postweaning handling to docility, prior learning sophistication, and differential shock intensity. In this 2-stage paradigm, with 32 wild and 32 hooded Long-Evans rats, escape and avoidance behaviors of wild and laboratory Ss were indistinguishable. Sophistication in laboratory-learning experience and high shock contributed significantly to the performance of both wild and domestic Ss in 1-way, but not 2-way, avoidance. In contrast, effects of handling were apparently negligible. Findings do not support the notion of degeneracy of learning ability in the domesticated rat. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of the nonagouti pelage-color allele on the behavior of captive wild Norway rats (Rattus norvegicus).

The objective of the present study was to determine the extent to which the nonagouti pelage-color allele influences selected behaviors (including docility) of the wild Norway rat. Agouti and nonagouti (black) littermates were compared in tests for handling, open-field behavior, platform jumping, and response to a novel food item, all of which clearly differentiate wild and domestic rats. Nonagouti rats were significantly easier to approach, capture, and handle than their agouti sibs. However, differences between agouti and nonagouti rats for the other variables studied were not significant. Although the presence of the nonagouti allele cannot fully account for the behavioral differences between wild and domestic Norway rats, it may have facilitated the domestication of this species by improving ease of handling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct contact with enriched environment is required to alter cerebral weights in rats.

To test the relative effectiveness of direct vs indirect interaction with an enriched environment, 2 experiments were conducted with Berkeley S1 rats. Some Ss were housed in groups of 12 in large enriched condition (EC) cages while littermate "observer" (OC) Ss were placed singly in small wire-mesh cages within EC. A 3rd group was housed singly in an impoverished condition (IC) where stimulation was minimal. After 30 days, Ss were killed and the brains dissected. In both experiments the usual pattern of EC-IC differences in brain weights appeared, whereas OC showed no significant differences from IC. On measures of exploratory behavior taken during the last 2 days of Exp II, IC fell significantly below EC, and OC was somewhat below IC. Thus EC differed from both IC and OC in brain and in behavior. Active contact with an enriched environment appears necessary for development of EC effects. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social deprivation and stimulus satiation in the albino rat.

Conducted 2 experiments, with a total of 288 male Sprague-Dawley albino rats, to explore the mechanisms whereby social deprivation leads to increased sociability in rats. Exp I housed Ss alone or in pairs with additional nonsocial stimulation, with additional response opportunities, or with no added social surrogates for 3 wks prior to testing for sociability. Social deprivation led to a strong increase in sociability, and this was not ameliorated by stimulus or response enrichment. Exp II exposed alone or pair-housed Ss to handling, human contact, or no stimulation and found that human exposure did serve a social surrogate function. This result suggests that sociability in rats represents to some degree a search for complex and unpredictable stimulation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of repeated testing on sexual behavior of the female rat.

Investigated effects of stimulation during repeated testing, using 24 female Sprague-Dawley rats in which intromission was prevented by a vaginal mask. Ss were ovariectomized and administered 1 mg of estradiol benzoate (EB) daily for 10 days (Exp I) or 5 mg of EB for 2 days (Exp II). Behavioral indices included lordosis quotient (a measure of sexual receptivity) and rejection quotient (a measure of social rejection of the male). Intensity and duration of lordosis gave additional measures. In Exp I hourly testing increased lordosis quotient and duration, especially in Ss receiving EB for 5 days; no effects of daily testing were shown. Exp II compared the behavior of Ss that were either handled hourly and tested hourly with the male rat or only handled hourly to the behavior of Ss that were tested and handled only once. Repeated testing and/or handling facilitated sexual responsiveness, while Ss that received neither treatment were sluggish in their social response to the male rat when they were tested, and were not sexually receptive. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term retention of avoidance learning by immature and adult rats as a function of environmental enrichment.

Taught 32 23-day-old female Sprague-Dawley albino rats active or passive avoidance. 32 controls received equivalent handling and shock in a different apparatus. Both groups were then exposed to an enriched or standard laboratory environment for 60 days prior to a retention test. Environmental enrichment resulted in greater forgetting of active avoidance. The lack of initial latency differences between control groups together with other indices of activity suggested that the differential forgetting was due to memorial effects rather than environmentally induced activity differences. Exp. II with 26 Ss indicated that environmental enrichment resulted in greater forgetting for both weanlings and adults, implicating extraexperimental interference as a general source of incomplete retention by the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response restriction during exposure to inescapable shock upon subsequent one-way and shuttle-avoidance performance in rats.

Investigated the effects of signaled inescapable shock on subsequent avoidance performance in 3 experiments with male Holtzman rats (N = 188). Exp I indicated that prior shock exposure (PSE) facilitated 1-way and shuttle avoidance. When Ss were preshocked in a harness so that free mobility was not possible, the facilitative effects of PSE on shuttle, but not 1-way avoidance performance, were largely reduced. Exp II indicated that activity during CS periods following PSE was greater among unrestrained than restrained Ss. Exp III showed that immobilization via injection of succinylcholine chloride did not affect the facilitative effects of PSE relative to that of Ss preshocked in a harness. Results are interpreted in terms of response repertoire changes produced by PSE in conjunction with the response requirement of the avoidance task. (French summary) (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Burrows of wild and albino rats: Effects of domestication, outdoor raising, age, experience, and maternal state.

Burrows dug by Sprague-Dawley albino rats were compared with those of wild Norway rats in an outdoor pen and in laboratory observation chambers in 5 experiments. In terms of measurements, configurations, or sequential development, burrows were indistinguishable in wild and domestic rats. Burrowing for both wild and domestic Ss was not affected by raising in outdoor burrows, by availability of nesting material, or by pregnancy. Prior experience in burrowing did make it more efficient in a 2nd trial, suggesting that learning may have a limited role in what appears to be a behavior with a strong genetic component. Feralization of domestic rats in the outdoor pen was especially productive in answering claims of degeneracy in these Ss: Albino rats were hardy throughout climatic extremes, maintained a stable population for 2 yrs, constructed and lived in burrows, and showed a variety of wild-type behaviors. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-compound learning with US presentation in taste aversion.

Determined whether the presentation of a LiCl unconditioned stimulus/stimuli (UCS) disrupts within-compound learning in a taste aversion preparation, using 30 male and 32 female rats in 3 experiments. In Exp I, Ss showed stronger associations between 2 solutions presented in a compound when the compound was followed by LiCl. Exp II showed that an immediate LiCl injection produced stronger flavor–flavor association than a delayed injection. Exp III provided a comparison with Ss that did not receive the treatment to enhance consumption of salty solutions. Results indicate that the effects of Exp II depended on the treatment that altered consumption of 1 component. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of naltrexone and signaling inescapable electric shock on nociception and gastric lesions in rats.

Two experiments, with 144 male Long-Evans hooded rats, examined the antinociceptive effects of signaled shock and its physiological underpinnings. In Exp I, Ss were exposed to 1 of 3 shock conditions: no shock, unsignaled shock, and signaled (by a 10-sec, 1,000-Hz tone) shock. In each condition, Ss were tested hourly in the absence of tones for nociception, with vocalization to shock used as the behavioral measure. Ss receiving signaled shocks had stomach ulcer scores intermediate between those of no-shock and unsignaled shock Ss. Signaled-shock Ss also displayed a pronounced vocalization antinociception effect. This suggested that signaled shock may be less aversive. Exp II investigated a possible role of endogenous opiate peptides in these effects. Ss received hourly injections of either the opiate antagonist naltrexone (7 mg/kg, ip) or saline. There were no significant effects of naltrexone on either stomach pathology or nociception scores. The same effects of signaled shock were obtained as in Exp I. It is concluded that the role of endogenous opiates in the effects of signaled shock seen here is minimal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Residual effects of food deprivation on food consumption and runway performance in the satiated rat.

2 experiments studied the residual effects of prior food deprivation in 35 female and 28 male Holtzman rats as measured by probability to eat and acquisition of a running response under satiated conditions. Although the effects were positively related to the severity of prior deprivation (Exp II), a drive-conditioning interpretation was questioned because of 3 findings: (a) effects were not dependent on exposure to the test situation when Ss were deprived (Exp I and II); (b) prolonged testing during satiation increased rather than decreased the effects (Exp I and II); and (c) the instrumental response decreased only when reward was withheld (Exp I). (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory in pigeons on the radial maze.

A series of 7 experiments with 10 pigeons showed, contrary to recent suggestions that pigeons show little or no spatial memory on the radial maze, highly accurate performance by Ss on an 8-arm radial maze. In Exp I, Ss were trained on successive phases that raised the number of alleys to be remembered from 1 to 4. In Exp II, Ss were allowed to search the maze for food with all 8 arms open. Measures of spatial memory showed that Ss performed at a level equivalent to that found with rats in previous research by A. B. Bond et al (see record 1982-25052-001). In Exp III, testing with massed trials revealed proactive interference. Ss were able to form reference memory for subsets of baited and unbaited alleys in Exp VI. In Exp VII, Ss learned about quantities of food associated with 4 different alleys and ordered their alley choices from the largest to the smallest reward. Contrary to the previous findings with rats, Ss in Exp IV showed forgetting over retention intervals of 0–360 sec between forced and free choices. It is concluded that spatial memory in pigeons generally shows the same properties as that in rats. (49 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Response prevention and extinction of escape behavior: Duration, frequency, similarity, and retraining variables in rats.

Describes 3 experiments in which a total of 158 female hooded rats received escape training, response prevention, and then regular extinction. Following training, Ss in Exp I received 1 response-prevention trial lasting 0, 120, 240, or 400 sec, or multiple trials (6, 12, or 20) lasting 20 sec each. Extinction was faster as prevention duration or frequency increased. At each duration, extinction was faster following multiple- than following single-prevention trials. In Exp II Ss received "prevention" in the original escape situation or in similar or dissimilar situations. Extinction was faster as prevention and training situations increased in similarity. To evaluate the persistence of prevention effects, in Exp III Ss received shock retraining between prevention and regular extinction. Retraining attenuated but did not eradicate the effects of prevention. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual specificity effects on word stem completion: Beyond transfer appropriate processing?

Explored the determinants of perceptual specificity effects (PSEs) in visual word-stem completion. 256 undergraduates participated in 4 experiments. In Exp 1, Ss completed a stem completion task after a number-search task in study-condition and -case phases. Ss were assessed for their awareness of the study-task relationship and compliance with instructions. In Exp 2, retrieval instructions and study task were manipulated within Ss and between 4 study-test blocks. Ss in Exp 3 completed study-test blocks with unintentional test instructions as in Exp 2. In Exp 4, retention interval, and study-task and -case were manipulated within the Ss. In Exp 1, PSEs on the stem completion task depended on perceptual encoding when Ss' awareness of the study-test relationship was limited. In Exps 2–4, these effects depended on semantic encoding. PSEs after short retention intervals were independent of encoding task. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)