Relative taste thresholds for ethanol, saccharin, and quinine solutions in three strains of rats nonselected for ethanol: A comparative study.

C. P. Richter and K. H. Campbell (1940b) originally defined taste threshold as "the point at which the rats first indicated that they recognized a difference between the distilled water and the solutions" (p. 34). The present study sought to apply this simple behavioral measure to the investigation of strain differences in taste sensitivities, particularly with respect to predictive relationships in ethanol, saccharin, and quinine preference. Fawn-Hooded, Lewis, and Wistar rats were presented with gradual increments in concentration of ethanol (0.01-15%; C. P. Richter & K. H. Campbell, 1940a), saccharin (0.002-3%) or quinine (0.000 1-0.0055). Results showed that although intake for saccharin was similar in all strains, consumption of ethanol and quinine differed among the groups. Although previous research has proposed that sweet preference is a promising behavioral marker for ethanol preference, these results suggested that bitter preference may be a more reliable predictor of ethanol preference in rats. (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)     

Natural selection and "sudden death."

C. W. Hughes and J. J. Lynch's (see record 1979-12747-001) article supports arguments relating survival time of rats in the Richter swimming apparatus to ontogenetic, physiological, and situational variables. Experiences with the sudden death of zoo animals, particularly ungulates, are discussed with reference to this argument. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of families on intellectual development.

Comments that we know less than we think about the direct influence of environment on the causes of intellectual differences among individuals. It is valuable to examine the results of adoption studies, since some separation of hereditary and environmental influences can be achieved. Results suggest that factors such as parental education and intelligence have only a small impact on the intelligence of their children. A very large fraction of the environmental causes of individual differences remains unexplained. It is hypothesized that many of these influences are fortuitous and biological in nature. These factors can include unrecognized head injuries, viruses, and subtle inborn errors of metabolism; the latter leading to mismatches between the individual's genes and the specific environments to which he or she is exposed. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early experience in domestication.

Conducted 2 experiments to assess the ontogenetic as well as phylogenetic influences of early experience on domestication. A total of 40 Long-Evans hooded and 32 Sprague-Dawley albino domestic rats and 72 1st generation, laboratory-reared wild rats were the Ss. Exp I was a factorial, reciprocal cross-foster study. Exp II was a factorial assessment of the combined effects of preweaning handling and postweaning enriched environments. These experiments on rat domestication show that preweaning handling had a strong influence on the ontogenetic development of the S in terms of reduced emotionality. Handled wild Ss became much more like domestic Ss in their behavior. This finding for handling contrasted with minimal effects for cross-fostering and enriched environments. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and Environmental Influences on Marital Relationships.

As most adults will marry at least once during their lifetime, studying marital quality and its predictors is of great importance. The current study addresses (a) the extent of agreement between husbands and wives on their marital quality, (b) genetic and environmental sources of individual differences on spouse reports of marital quality, and (c) the extent to which genetic and environmental influences account for overlap of spouse reports on marital quality. Adult Swedish twin women and their partners participated in this study. Genotype-environment (GE) correlations were found for marital quality, suggesting that wives' genetically influenced characteristics set a tone for the marriage. Wives' genetically influenced characteristics also accounted for overlap of spouse reports of marital quality. Finally, nonshared environmental influences were the primary contributor to both individual reports and the overlap of spouse reports, an interesting deviation from findings of behavior genetic studies of other types of relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Explaining race differences in IQ: The logic, the methodology, and the evidence.

Examines the claim that there are genetic racial differences in IQ, which has been based mainly on 2 grounds: the evidence for high within-race heritability for IQ and the failure of various environmental explanations to account completely for mean racial differences. It is argued that neither of these trends has direct relevance to the question of whether race differences in IQ have a mainly genetic or environmental origin. The assumption that these factors are relevant and that they support a genetic account is criticized as a "hereditarian fallacy." The choice between a genetic and an environmental account of race differences is most properly based on jointly genetic/environmental designs, which control for both genetic and environmental differences in a behavior genetic framework. Studies using environmental, genetic, and joint models are reviewed. Although evidence tends to support an environmental over a genetic account, it is not considered to be sufficient. Identification of what the relevant environmental differences may be would require turning away from the traditional heredity vs environment question and focusing on the detailed causal influences that affect the development of intellectual level generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Environmental complexity, cerebral change, and behavior.

The overall program relating brain processes to behavior in animals concerns both hereditary and environmental factors that have been demonstrated to affect learning ability. Rats subjected to an enriched environment (involving environmental complexity and training) "consistently develop greater weight of cerebral cortex than do their impoverished littermates… [and] the cortical/subcortical weight ratio is consistently greater for the enriched than for the restricted rats… ." The average diameter of capillaries in the cortex is greater in enriched than in impoverished animals. The total activity of acetylcholinesterase is found to increase slightly but consistently in the enriched animals. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sudden death in the laboratory rat: cardiac function, sensory, and experiental factors in swimming deaths

Three reported charateristics of sudden death in the wild rat, (1) bradycardia, (2) decreased survival without whiskers, and (3) increased suvival with preexposure to the stressor, are demonstrated in the domestic rat. Differences in sudden death between wild and domestic rats are discussed as well as possible interpretations of the phenomenon.     

Effect of the post-weaning environment on the climbing behaviour of wild and domestic Norway rats

The climbing behaviour of wild and domestic Norway rats (Rattus norvegicus) was compared after early rearing in three post-weaning environments offering different climbing experiences. Wild rats climbed in the test apparatus even when denied early climbing experience; male domestic rats did not. Early climbing experience increased the climbing scores of both stocks but influenced the climbing proficiency of wild rats only. Treatment differences in climbing behaviour may be related to specific motor experiences gained during development and the effect of early experience on the response to a novel environment (test apparatus). Stock differences in climbing behaviour may reflect a general reduction in motor activity among domestic rats and their reduced sensitivity to stimulus change or novelty.     

Child effects—still unwelcome? Response to Dodge and Wahler.

Commentaries by K. A. Dodge (see record 1991-04756-001) and R. G. Wahler (see record 1991-04823-001) agree with Lytton (see record 1991-04795-001) on the importance of drawing attention to the joint action of biological and environmental factors in conduct disorder (CD). This article is a response restating why it is useful to try to disentangle "child effects" from "parental effects." Although each construct is an amalgam of genetic/biological and environmental factors, child effects will be nearer the biological end, and parental treatment effects nearer the environmental end, of a spectrum of influences. Ten convergent lines of research, taken together, provide evidence that has persuaded me that the child's own tendencies are stronger contributions to CD than are parental influences. Others should at least consider the evidence. (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)     

Reduction of cognitive dissonance by seeking consonant information.

"An experiment was conducted to test two hypotheses about the reduction of cognitive dissonance by seeking information. The hypotheses were: (a) a person in whom dissonance has been produced by exposure to a communication advocating an opinion contrary to the person's is more likely to seek information than a person exposed to a compatible communication, and (b) a person in whom dissonance has been produced by a contrary communication tends to seek information from a source agreeing with his opinion. The opinions of 100 mothers on the importance of hereditary and environmental factors in child rearing were ascertained by personal interview; they were then exposed to a tape recorded, authoritative communication espousing a hereditary or an environmental point of view… . The results supported the first hypothesis." From Psyc Abstracts 36:01:3GG74A. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroendocrine correlates of emotional reactivity and coping in male rats from the Roman high (RHA/Verh)- and low (RLA/Verh)-avoidance lines

The Roman high (RHA/Verh)- and low (RLA/Verh)-avoidance rats, originally selected and bred for rapid vs. poor acquisition of a two-way active avoidance response, differ in emotional reactivity and sensitivity to stressors in various other test situations. These behavioral differences are associated with particular neuroendocrine and neurochemical characteristics. The aim of this short review is to present data currently available on the neuroendocrine profiles of RHA/Verh and RLA/Verh rats, together with more recent findings which suggest that differences in peripheral and central hormonal responses, and in hormone action on the brain, may be closely related to emotional reactivity and coping ability. Although genetic factors certainly play a major role, there is also evidence that epigenetic factors, e.g., early environmental influences, can modulate the phenotypic expression of the basic behavioral and neuroendocrine traits characterizing these lines. These psychogenetically selected lines can therefore be used as a model to investigate interactions between genes and the environment in determining each individual's sensitivity to stress and coping abilities ("vulnerability" model). This model may prove particularly useful for studies on the etiology and pathophysiology of anxiety and affective disorders and their neuroendocrine correlates.     

Constitution and body proportions in different strains of rats. A study of race formation in breeding isolates

(1) There are considerable differences in body constitution in different strains of rats, ranging from very robust to very gracile forms. The differences are greater in the larger males than in the smaller females. (2)Craniofacial and postcranial proportions of the trunk in domesticated strains of rats differ either uniformly or mosaically from the wild form. (3)Nasal shape differs greatly in rats ranging from extreme leptorrhine to extreme platyrrhine forms, giving a total range greater than in human populations. (4)Fisher 344 rats have long tails and extremities and Buffalo and GRL short tails and extremities. (5)Wistar and ACI rats have longer tails than wild rats but do not differ significantly from wild rats in the relative length of their other extremities. (6)The relationship between tail and extremity length is under genetic control which is concordant in Fisher, Buffalo and GRL rats, but discordant in the Lewis, Wistar and ACI strains. (7)There is no connection between relative extremity length and total body constitution since short-limbed strains occupy both the highest (Buffalo) and lowest (GRL) levels o f robusticity, and strains that do not differ in relative extremity length from wild rats differ greatly from each other in constitutional type (Wistar and ACI). (8)Differences of relative extremity length and nasal shape in rats have their parallels in human populations. But in human populations they follow Allen's ecological "rule" and can be duplicated experimentally. In rats here used, however, they do not result from any known ecological pressures, but from the genetic factors acting in breeding isolates.     

Environmental and genetic influences on prereading skills in Australia, Scandinavia, and the United States.

Individual differences in measures of prereading skills and in questionnaire measures of 4-5-year-old twins' print environments in Australia, Scandinavia, and the United States were explored with a behavioral-genetic design. Modest phenotypic correlations were found between environmental measures and the twins' print knowledge, general verbal ability, and phoneme awareness. Lower print knowledge in Scandinavian twins was related to country differences in preschool print environment. Latent-trait behavioral-genetic analyses indicated very strong shared-environment influences on individual differences in Print Knowledge. Genetic influence was also significant. Several other prereading skills varied in their environmental and genetic influence, including a significant contrast between Phonological Awareness and Print Knowledge. Rapid Naming also revealed very strong genetic influence, as did Verbal Memory. Stronger shared-environment influences were found for Vocabulary and Grammar/Morphology. Genetic and environmental correlations among latent traits for General Verbal Ability, Phonological Awareness, and Print Knowledge were high, but there were also significant independent genetic and environmental contributions to each skill. Practical implications include the need for substantial and sustained instructional support for children hampered by genetic constraints on early literacy development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Desegregation and the intellectual performance of the Negro: Comment.

I should like to make three criticisms of Irwin Katz' timely and stimulating article, "Review of Evidence Relating to Effects of Desegregation on the Intellectual Performance of Negroes" (see record 1965-01781-001). My first criticism is that the author failed to include in his extensive bibliography reference to several pertinent studies/papers. My second criticism is directed against the author's failure to consider the possibility of hereditary differences between Negro and white children. My third criticism is directed toward the widespread tendency of psychologists to neglect the importance of heredity as a determinant of behavior, personality, and even of the environment. (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)     

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)     

Testing hypotheses on specific environmental causal effects on behavior.

There have been strong critiques of the notion that environmental influences can have an important effect on psychological functioning. The substance of these criticisms is considered in order to infer the methodological challenges that have to be met. Concepts of cause and of the testing of causal effects are discussed with a particular focus on the need to consider sample selection and the value (and limitations) of longitudinal data. The designs that may be used to test hypotheses on specific environmental risk mechanisms for psychopathology are discussed in relation to a range of adoption strategies, twin designs, various types of "natural experiments," migration designs, the study of secular change, and intervention designs. In each case, consideration is given to the need for samples that "pull-apart" variables that ordinarily go together, specific hypotheses on possible causal processes, and the specification and testing of key assumptions. It is concluded that environmental risk hypotheses can be (and have been) put to the test but that it is usually necessary to use a combination of research strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)