Detailed analysis of the male copulatory motor pattern in mammals: hormonal bases

Data obtained, using a polygraphic technique, on the characteristics of the motor and genital copulatory responses of male rabbits, rats, mice, hamsters, and guinea pigs are reviewed. This methodology provided detailed information, not accessible to other analyses, on the frequency and dynamic organization of copulatory pelvic thrusting trains of the species studied. This comparative analysis showed that: (1) The male rat may display two types of ejaculatory responses, differing in the dynamic organization of the pelvic thrusting train, and in the duration of the intravaginal thrusting period preceding ejaculation. (2) In the guinea pigs and small rodents, but not in rabbits, pelvic thrusting at ejaculatory responses persists during intromission, and a period of fast intravaginal thrusting is associated with ejaculation. (3) The motor copulatory pattern of the rabbit, but not of the rat, hamster, or guinea pig, is affected by castration and hormone treatment, suggesting that, in rabbits, androgen acts both on motivation and on the spinal neural systems related to copulation.     

Explaining individual differences in scholastic behaviour and achievement

Background. This paper presents results from the first wave of a longitudinal study examining the effects of various psychosocial variables on scholastic achievement and behaviour at school. Aims. The main aim is to investigate the nature and strength of the effects of major individual difference dimensions on important outcome variables at school level, including academic performance, truancy, and antisocial behaviour. Samples. Data were collected from a sample of 901 pupils on verbal ability (as a proxy for cognitive ability), personality traits, and a number of behavioural indices, including academic performance at 14 and 16 years, number of authorized and unauthorized absences, and exclusions from school due to antisocial conduct. Methods. During the first stage of the study, seven schools participated in all three phases. Teachers administered a questionnaire battery in class according to a detailed protocol. Additional data were collected from school archives. Results. Analysis of the data through multi‐group (male and female puplis) structural equation modelling indicated a very strong effect of verbal ability on academic performance. Extraversion and psychoticism were negatively related to academic performance, although their effects were weak and moderated by gender. Verbal ability, extraversion, and psychoticism predicted absenteeism, truancy, and exclusions from school due to disruptive conduct. The latter three were negatively associated with academic performance. Conclusions. The findings indicate that major individual difference dimensions like verbal ability and personality traits, have a strong influence on important outcome variables at school level, including academic performance, truancy, and antisocial behaviour. Without fully acknowledging the crucial role of individual differences in shaping behaviour and achievement at school, the timely identification of pupils at risk, and the development of effective intervention schemes will be difficult.     

The backpropagation algorithm: Implications for the biological bases of individual differences in intelligence

Variations in brain structure and function may explain individual variation in human intelligence. However, it is not currently possible to directly examine this hypothesis. As an indirect examination, a neural network employing the backpropagation algorithm to solve the exclusive-or function was manipulated to possess different numbers of processing elements (neurons), connections (synapses), and conduction failure (synaptic failure). The effect of the variations on network accuracy and energy utilization were compared to human reaction time and cerebral metabolic data to evaluate which variations most reliably reproduced the human results. Varying the synaptic failure rate appears essential for mimicking the human reaction time data and increasing network connectivity is the most efficient way to improve network accuracy for a given degree of neuronal activation. The results suggest that variations in the physiologic events of synaptic neurotransmission and variations in the structural interconnectivity of the neurons in the brain will be found to underline an important portion of the variation in human intelligence.     

Social roles and social perception: individual differences in attribution and error

In a replication of the social roles experiment by Ross, Amabile, and Steinmetz (1977), 103 male and female 14-year-olds viewed a brief videotape that showed a randomly assigned "questioner" asking general knowledge questions of a "contestant," who answered most of them incorrectly. Subjects subsequently manifested the role-based attribution error of attributing significantly more knowledge and ability to the arbitrarily designated questioner than to the arbitrarily designated contestant, and this effect was stronger among girls than boys. Personality data were available on the subjects for when they were in nursery school and again at age 14 in the form of independent Q-sort ratings. Personality correlates of the role effect were stronger among boys but manifested a basically similar pattern among girls and suggested that those most prone to make this attribution error, far from being disadvantaged in social judgment, tended to be more socially engaged and competent as well as emotionally well adjusted. The role effect was also positively associated with self-esteem. Personality correlates of attributional generosity and the tendency to attribute high ability to stimulus persons were associated with generally positive interpersonal qualities and attitudes. Results were interpreted in terms of usually appropriate heuristic social competencies that, in special circumstances, may sometimes underlie attribution errors. The general usefulness of examining individual differences in research on social cognition was noted.     

Aggressive behaviour elicited in rats by different social situations. Analysis of aggressive patterns and individual differences

In the present work, we have analyzed aggressive patterns shown by rats reared in different social situations. The mixed colonial group shows significantly lower scores in those behaviour patterns which are grouped in the Physical Attack factor, and mixed colonial rats are the ones that score highest in those behaviour patterns which are grouped in the Expectancy factor. Thus, these animals are the ones that show more Expectancy and less Physical Attack. The presence of female rats in mixed colonies would increase the Expectancy. In a situation where there is no artificial manipulation (male colonies) or in which the intervention is small (mixed colonies) correlation between those factors (Physical Attack and Expectancy) is high, that is to say, these factors are close to one another. But when there is a clearer interference, like social isolation, the two factors separate and reveal themselves to be independent from one another. Thereafter, we have analyzed the possible influence of individual differences in a low-frightening Open Field in aggressive behaviour. On the Physical Attack factor the interaction Ambulation-Defecation is nearly significant and the correlations of Ambulation and Defecation with Physical Attack are positive and negative, respectively and nearly significant in mixed colonies but not in isolated rats. We suggest in accordance with Karli, Vergnes, Eclancher, Schmitt and Chaurand (1972) that in an appetite situation the less fearful rats (low defecatory and high ambulatory rats) attack with higher frequency and intensity.     

The relationship between individual differences in intraindividual variability in core affect and interpersonal behaviour

How people's feelings and interpersonal behaviour change across time can be represented as movements within a core affect and an interpersonal space. To gain insight into the relationship between affect and behaviour dynamics, the present study examined how individual differences in intraindividual variability in core affect relate to those in interpersonal behaviour, and how both are related to personality traits. In an experience sampling study, 63 participants were asked to monitor their core affect during one week and their interpersonal behaviour during another one. The results demonstrated a fairly consistent correspondence between several indices of people's variability in core affect and interpersonal behaviour, indicating that emotional lability also signals behavioural volatility and vice versa. Copyright © 2010 John Wiley & Sons, Ltd.     

Social inference and individual differences in aggression: Evidence for spontaneous judgments of hostility

This research examined the hypothesis that aggressive vs. nonaggressive individuals differ in their spontaneous trait inferences, i. e., inferences made without any conscious intention of inferring characteristics of an actor. We anticipated that spontaneous processing conditions would be more revealing of aggressive/nonaggressive differences than would conditions that prompt deliberate inference processes. We used a cued-recall paradigm. Aggressive and nonaggressive subjects were instructed to memorize sentences that were open to either hostile or nonhostile interpretations. Sentence recall was then cued by either hostile dispositional terms or by words that were linked semantically to the element of the sentences. Within the spontaneous inference condition, semantic cues prompted twice as much recall as hostile cues among nonaggressive subjects, whereas dispositional cues aided recall more than semantic cues among aggressive subjects. As predicted, within the delinerate inference conditions there were no aggressive/nonaggressive differences. The nature of spontaneous vs. deliberate inferential processes and the advantages of spontaneous inference paradigms for testing predictions about schema-based processing in aggression are discussed. © 1995 Wiley-Liss, Inc.     

A mathematical model of the evolution of individual differences in developmental plasticity arising through parental bet‐hedging

Children vary in the extent to which their development is shaped by particular experiences (e.g. maltreatment, social support). This variation raises a question: Is there no single level of plasticity that maximizes biological fitness? One influential hypothesis states that when different levels of plasticity are optimal in different environmental states and the environment fluctuates unpredictably, natural selection may favor parents producing offspring with varying levels of plasticity. The current article presents a mathematical model assessing the logic of this hypothesis – specifically, it examines what conditions are required for natural selection to favor parents to bet‐hedge by varying their offspring's plasticity. Consistent with existing theory from biology, results show that between‐individual variation in plasticity cannot evolve when the environment only varies across space. If, however, the environment varies across time, selection can favor differential plasticity, provided fitness effects are large (i.e. variation in individuals’ plasticity is correlated with substantial variation in fitness). Our model also generates a novel restriction: Differential plasticity only evolves when the cost of being mismatched to the environment exceeds the benefits of being well matched. Based on mechanistic considerations, we argue that bet‐hedging by varying offspring plasticity, if it were to evolve, would be more likely instantiated via epigenetic mechanisms (e.g. pre‐ or postnatal developmental programming) than genetic ones (e.g. mating with genetically diverse partners). Our model suggests novel avenues for testing the bet‐hedging hypothesis of differential plasticity, including empirical predictions and relevant measures. We also discuss several ways in which future work might extend our model.     

Trends in the psychophysiology of individual differences

Pavlov’s typology of higher nervous activity was the first systematic approach to the psychophysiology of individual differences. Pavlov’s theory has been further developed by Teplov, Nebylitsyn and their pupils in the Institute of Psychology in Moscow. In particular, Nebylitsyn has delineated a new property of the nervous system and has shown that it is different from strength of nervous system. In the Western research context we can compare the relationship between these two parameters to that between arousal and conditioning level. Eysenck’s theory of the physiological bases of extraversion/introversion is discussed in relation to Nebylitsyn ’s theses and Gray’s conception of arousability. Finally, it is suggested that future work in the psychophysiology of individual differences should stress the study of the ontogenetic development of the physiological variables.     

Process differences and individual differences in some cognitive tasks

This study is based on three distinct elementary cognitive tasks (ECTs) using chronometric techniques: (a) the S. Sternberg memory scan task, (b) a visual scan task which is perfectly analogous to the memory scan, except that the target digit is presented first and the subject must then scan a set of digits and indicate the presence or absence of the target digit in the set, and (c) the Hick paradigm, which involves responding to a visual stimulus (a light going “on”) when the stimulus is one among sets of either 1, 2, 4, or 8 equally probable alternatives. Certain parameters of all three tasks, such as intercept and slope of RT as a function of set size, from which different cognitive processes are inferred, are compared experimentally and correlationally. Subjects were 48 university students, tested and retested on the three tasks in a counterbalanced design on two separate days to obtain the retest reliabilities needed to correct all correlations for attenuation. Subjects were also given Raven's Advanced Progressive Matrices as a measure of psychometric g. Parameters of the ECTs are significantly and, in some cases, quite substantially correlated with g. Virtually all of this correlation is due to the general factor of the various ECTs, rather than to specific processing components (independent of the general factor). The results also indicate that different ECT paradigms (e.g., visual search and memory search tasks) may yield markedly different values in terms of the group means of analogous parameters, indicating different processes, and yet not show independence of the parameters in terms of individual differences; that is, measurements of the different parameters in individuals are perfectly correlated (i.e., disattenuated correlations do not differ significantly from r = 1). This is found for the intercept parameter of visual and memory search. The reverse condition is also found for the other parameters (e.g., slope); that is, their mean values are nearly identical, suggesting the same processes, yet disattenuated correlations between individual differences are relatively low, or even negative, indicating different processes. Although the general factor clearly predominates, it does not completely overwhelm individual differences in various component processes that are distinct from the general factor.     

Social evaluation fear in childhood and adolescence: Normative developmental course and continuity of individual differences

Using cross‐sectional (N =910) and longitudinal (N =261) data from Gullone and King's (1993, 1997 ) studies of normal fear in children and adolescents aged 7 to 18 years, the normative developmental pattern of social evaluation fear and the continuity of individual differences were investigated. Participants' responses were analysed according to two subscales (Social Evaluation and Punishment) within the Failure and Criticism scale of the Fear Survey Schedule. The findings indicated that: (a) social evaluation fear increased between childhood and adolescence, while punishment fear decreased, (b) individual differences in social evaluation fear displayed only modest continuity over the 3‐year follow‐up period, (c) continuity of social evaluation fear increased with increased age and (d) discontinuity was particularly salient for relatively high fear levels.     

Domain-specificity and individual differences in worry

Worrying is generally perceived to be an undesirable mental state. An evolutionary approach suggests, however, despite the potential distress, worry may function to focus individuals’ attention on evolutionarily-relevant tasks. In the current study (N = 193), we demonstrated that participants’ primary worries were focused within domains central to reproductive success and mate-value. Furthermore, mating strategy predicted worries in the domains of social status and mating. Neuroticism, as an individual difference reflecting vigilance to threats, was correlated with worry about fitness-relevant but not fitness-irrelevant domains. The current study documents the first domain-specific assessment of worries and complements this analysis with intriguing individual difference predictors of worry.     

Social value related response latencies: Unobtrusive evidence for individual differences in information processing

While much research concerning decision-making in interdependency situations concentrates on the influence of social values or different preferences for certain distributions of outcomes for self and other (McClintock, 1978), little attention has been paid to the cognitive processes underlying the expression of these different social values. The present research focuses on the cognitive processes by examining the influence of the dominant social values on decision-makers' response latencies (RLs) in interdependency situations. Using the Ring Measure of Social Values (Liebrand 1984), three experiments were conducted to assess these RLs. Experiment 1 examines the reliability of the social value construct and the RL effect. Experiments 2 and 3 investigate the generality of the RL effect across presentation of combinations of own and other's outcomes (all positive versus all negative). As predicted, RLs were shorter for individualists than for cooperators and competitors. Further, regardless of values, shorter RLs occurred across experiments when own outcomes are positive rather than negative. More important, the predicted interaction between social value and outcome distribution was observed, reflecting increasing RLs for cooperators as their joint outcomes decreased, longer RLs for individualists when own outcomes were negative rather than positive, and longer RLs for competitors when they were outcome disadvantaged rather than advantaged relative to other. These findings are consistent with the expectation that (I) the transformations associated with different social values require different cognitive processes, and (2) subsequent to the value transformations of outcomes, RLs increase when the utility of the transformed outcome distributions decreases.