Knowledge that Transforms

Although it has long been recognized that there is increased risk of divorce among the children of divorced parents, the extent to which genetic and environmental factors contribute to this familial resemblance has been a matter of speculation only. In order to resolve the separate influence of genetic and environmental factors on risk of divorce, divorce status of 1,516 same-sex twin pairs (722 monozygotic. MZ, and 794 dizygotic. DZ), their parents, and their spouses' parents was determined. Concordance for divorce was significantly higher in MZ than DZ twins; this was true overall, in both the male and female samples, for both younger and older twin pairs, and both when the twins' parents had been divorced and when they had not been divorced. The robustness and magnitude of the MZ-DZ difference in divorce concordance indicates a strong influence of genetic factors in the etiology of divorce. Moreover, family background of both spouses contributed independently to couples' divorce risk, suggesting that, in many cases, divorce may be largely the result of characteristics the two spouses bring to the union rather than to interaction effects. These results also suggest that the adjustment difficulties seen with some children of divorced parents may be due to an interaction between genetic and environmental factors rather than environmental influences alone, as is assumed in many theories of divorce's effects.

Girls with congenital adrenal hyperplasia (CAH) who were exposed to high levels of androgen in the prenatal and early postnatal periods showed increased play with boys” toys and reduced play with girls' toys compared with their unexposed female relatives at ages 3 to 8. Boys with CAH did not differ from their male relatives in play with boys' or girls' toys. These results suggest that early hormone exposure in females has a masculinizing effect on sex-typed toy preferences.

Research on cerebral asymmetry and the experience and expression of emotion is reviewed. The studies described use electrophysiological procedures to make inferences about patterns of regional cortical activation. Such procedures have sufficient temporal resolution to be used in the study of brief emotional experiences denoted by spontaneous facial expressions. In adults and infants, the experimental arousal of positive, approach-related emotions is associated with selective activation of the left frontal region, while arousal of negative, withdrawal-related emotions is associated with selective activation of the right frontal region. Individual differences in baseline measures of frontal asymmetry are associated with dispositional mood, affective reactivity, temperament, and immune function. These studies suggest that neural systems mediating approach- and withdrawal-related emotion and action are, in part, represented in the left and right frontal regions, respectively, and that individual differences in the activation levels of these systems are associated with a coherent nomological network of associations which constitute a person's affective style.

Following decades of controversy and uncertainty, there is now sufficient empirical basis for asserting the existence of a limited set of autonomic differences among emotions. Findings of autonomic distinctions among emotions-derived from the work of the author and his colleagues using two methods of emotion elicitation are reviewed. For five of these autonomic distinctions, convergent findings from the work of other investigators using the same and other elicitation methods are presented.

The evidence on universals in facial expression of emotion, renewed controversy about that evidence, and new findings on cultural differences are reviewed. New findings on the capability for voluntarily made facial expressions to generate changes in both autonomic and central nervous system activity are discussed, and possible mechanisms by which this could occur are outlined. Finally, new work which has identified how to distinguish the smile of enjoyment from other types of smiling is described.

Choice often produces conflict. This notion, however, plays no role in classical decision theory, in which each alternative is assigned a value, and the decision maker selects from every choice set the option with the highest value. We contrast this principle of value maximization with the hypothesis that the option to delay choice or seek new alternatives is more likely to be selected when conflict is high than when it is low. This hypothesis is supported by several studies showing that the tendency to defer decision, search for new alternatives, or choose the default option can be increased when the offered set is enlarged or improved, contrary to the principle of value maximization.

In species with internal female fertilization, males risk both lowered paternity probability and investment in rival gametes if their mates have sexual contact with other males. Females of such species do not risk lowered maternity probability through partner infidelity, but they do risk the diversion of their mates' commitment and resources to rival females. Three studies tested the hypothesis that sex differences in jealousy emerged in humans as solutions to the respective adaptive problems faced by each sex. In Study 1, men and women selected which event would upset them more—a partner's sexual infidelity or emotional infidelity. Study 2 recorded physiological responses (heart rate, electrodermal response, corrugator supercilii contraction) while subjects imagined separately the two types of partner infidelity. Study 3 tested the effect of being in a committed sexual relationship on the activation of jealousy. All studies showed large sex differences, confirming hypothesized sex linkages in jealousy activation.

Bartlett (1932) gave subjects a prose passage and showed how recall dropped when they were tested repeatedly. Ballard (1913), using poetry, and Erdelyi and Becker (1974), using pictures, reported improvements in performance (or hypermnesia) over repeated testing. We investigated two likely factors leading to the discrepant results: the type of material and the interval between tests. The primary cause of the differing outcomes is the interval between tests. In general, when the intervals between successive tests are short improvement occurs between tests. When these intervals are long, forgetting occurs. The type of material used plays little role: Hypermnesia in recall of prose (even “The War of the Ghosts”) occurred with short intervals between tests. We also report a striking confirmation of the power of tests to enhance memory: Repeated tests shortly after study greatly improved recall a week later.

We argue herein that typical training procedures are far from optimal. The goat of training in real-world settings is, or should be, to support two aspects of posttraining performance: (a) the level of performance in the long term and (b) the capability to transfer that training to related tasks and altered contexts. The implicit or explicit assumption of those persons responsible for training is that the procedures that enhance performance and speed improvement during training will necessarily achieve these two goals. However, a variety of experiments on motor and verbal learning indicate that this assumption is often incorrect. Manipulations that maximize performance during training can be detrimental in the long term; conversely, manipulations that degrade the speed of acquisition can support the long-term goals of training. The fact that there are parallel findings in the motor and verbal domains suggests that principles of considerable generality can be deduced to upgrade training procedures.

Human adults with normal vision, with three types of color-blindness, or with complete absence of vision since birth rank-ordered the similarities of all pairs of colors corresponding to nine hue names. When presented with the names only, subjects with any color vision produced rankings for which multidimensional scaling yielded Newton's color circle. When subjects were presented with the colors themselves, the recovered color circle remained the same for the normally sighted but collapsed along the red-green dimension for the color-blind. Based on their rankings by color names, the totally blind subjects all fell outside the range of the color-normal subjects but partly overlapped the color-deficient subjects; a rare rod monochromat roughly approximated the color-normal subjects. These results, along with those of Marmor (1978) and Izmailov and Sokolov (this issue), suggest how visual experience, language, and innate structure contribute to the mental representation of colors.