Handedness in wild chimpanzees

The debate over nonhuman primate precursors to human handedness is unsettled mainly due to lack of data, particularly on apes. Handedness in wild chimpanzees at the Taï National Park Côte d'Ivoire, has been monitored in four tasks. For the simple unimanual ones, reaching and grooming, adults use both hands equally (ambidextrous), while for the more complex unimanual wadge-dipping and the complex bimanual nut-cracking, adults are highly lateralized. These results support the hypothesis that lateralization increases with the complexity of the task. The lateralization is constant for years for each task but may vary in an individual with respect to different tasks. For nutcracking females are more lateralized than males. The ontogeny of handedness for nut-cracking shows many variations in the tendency to use one hand and in the side preferred, until at about 10 years of age, the individual achieves her adult handedness. No population bias toward one side exists in Taï chimpanzees. No heritability of handedness between mother and offspring was observed. Human and chimpanzees handedness are compared.     

Population-Level Right Handedness for a Coordinated Bimanual Task in Chimpanzees: Replication and Extension in a Second Colony of Apes

The purpose of this study was to evaluate the reliability of previously published findings on hand preferences in chimpanzees by evaluating hand use in a second colony of captive chimpanzees. We assessed hand preferences for a coordinated bimanual task in 116 chimpanzees (Pan troglodytes) at the University of Texas M. D. Anderson Cancer Center and compared them to previously published findings in captive chimpanzees at the Yerkes National Primate Research Center. The new sample showed significant population-level right handedness, which is consistent with previously published findings in the Yerkes chimpanzees. Combined data on the 2 chimpanzee colonies, revealed a significant effect of rearing history on hand preference, with wild-caught chimpanzees showing less right-handedness than captive-born mother-reared chimpanzees. We discuss the results in terms of the role of early environment on the development of laterality.     

The Dreams of Blind Men and Women: A Replication and Extension of Previous Findings

Drawing on a sample of 372 dreams from 15 blind adults, we present two separate analyses that replicate and extend findings from previous studies. The first analysis employed DreamSearch, a software program designed for use with dream narratives, to examine the appearance of the five sensory modalities. It revealed that those blind since birth or very early childhood had (1) no visual imagery and (2) a very high percentage of gustatory, olfactory, and tactual sensory references. The second analysis found that both male and female participants differed from their sighted counterparts in the same ways on several Hall and Van de Castle (1966) coding categories, including a high percentage of locomotion/transportation dreams that contained at least one dreamer-involved misfortune. The findings on sensory references and dreamer-involved misfortunes in locomotion/transportation dreams are interpreted as evidence for the continuity between dream content and waking cognition.     

Counterfactual Thought in Dreams

Counterfactual cognitive simulations are considerations of what might have been if what actually happened could be undone. I hypothesize that counterfactual thought is characteristic of dreams and that cognitive operations in dreams function to identify a norm violation recorded in autobiographical memory and then to re-instate normality in memory by generating counterfactuals to the violation. Dream counterfactuals therefore obey the same constraints on mutability as waking counterfactuals. Both dreaming and counterfactuals typically focus on the self, involve negative affect, and narrative form, promote problem solving and learning by running mental simulations and variations on a given problem theme, employ memory fragments in these various mental scenarios, plausibly rely on neural networks in right limbic and orbitofrontal cortices, and are largely automatic and pre-conscious operations.     

The Words of Adolescents' Dreams: A Quantitative Analysis

This research detects the most common words recurring in 326 adolescents' dream language. The analyzed dreams have been previously recorded and then transcribed. Grouping words, we obtained the frequency of the main parts of speech (nouns, verbs, adjectives and pronouns). Among the nouns, far more frequently represented are terms that refer to important objects of an affective relation. Other significant nouns relate to objects linked to both familial and extra-familial environments. Words related to family relations declined in frequency as age increased and were substituted by terms that refer to relations among friends and to the external world and its objects. Some of these results can be usefully compared with the conclusions derived from the application of other methods of content analysis. This method using dream language analysis could be applied to research concerning dream content, also through specific dictionaries (groups of words defined and classified in relation to a certain theme).     

A New Neurocognitive Theory of Dreams

Discoveries in three distinct areas of dream research make it possible to suggest the outlines of a new neurocognitive theory of dreaming. The first relevant findings come from assessments of patients with brain injuries, which show that lesions in different areas have differential effects on dreaming and thereby imply the contours of the neural network necessary for dreaming. The second set of results comes from work with children ages 3–15 in the sleep laboratory, which reveals that only 20–30% of REM period awakenings lead to dream reports up to age 9 and that the dreams of children under age 5 are bland and static in content. The third set of findings comes from a rigorous system of content analysis, which demonstrates the repetitive nature of much dream content and that dream content in general is continuous with waking conceptions and emotional preoccupations. Based on these findings, dreaming is best understood as a developmental cognitive achievement that depends upon the maturation and maintenance of a specific network of forebrain structures. The output of this neural network for dreaming is guided by a continuity principle linked to current personal concerns on the one hand and a repetition principle rooted in past emotional preoccupations on the other.     

The Consistency and Continuity Hypotheses Revisited through the Dreams of Women at Two Periods of their Lives

The purpose of the present longitudinal study was to determine the extent of consistency in dream content at two periods of adulthood as well as continuity with the psychosocial development of the dreamers. Twenty-one women kept a dream diary for a few weeks at intervals of 10, 15 or 17 years. ANOVAs for repeated measures were performed on the mean frequencies per dreamer of different dream elements or ratios of these elements. No significant changes were found. Pearson moment correlations yielded high and significant internal consistency for friendly and aggressive interactions. None of the others were significant. Ratios and indices calculated on subclasses of characters, settings, interactions and emotions revealed significant deviations from female norms, at one or the other of the phases. These different findings are discussed within the theoretical perspective of continuity with developmental stages in women's lives.     

Much Ado About Very Little: The Small Effect Sizes When Home and Laboratory Collected Dreams Are Compared

We report a reanalysis of the original codings of dream reports collected at home and in the sleep laboratory from the same participants studied by Hall and Van de Castle in 1964. We used Cohen'sh statistic for effect sizes to argue that, even when statistically significant, most of the differences between the two samples are small to medium in magnitude. This finding suggests that past arguments over the relative usefulness of the two types of samples might not have occurred if the magnitude of effect sizes had been taken into account. The one exception concerns aggressions of various kinds, which also show the greatest variability with age, gender, and culture. It is concluded that useful dream samples for studies using the Hall and Van de Castle coding system can be collected in the laboratory or from normal recall at home and that effect sizes should be calculated in all dream content studies.     

Content Analysis of German Students' Dreams: Comparison to American Findings

Studies have demonstrated that general dream characteristics, such as gender ratio and familiarity of dream characters, frequency and type of social interactions and settings, and gender differences (e.g., heightened physical aggression in men's dreams), are very stable over time and across different populations. The present study included 537 dreams of 106 women and 39 men (German students). The results confirmed earlier findings regarding the stability of general dream characteristics and gender differences. Only the gender difference regarding the gender ratio of dream characters has not been replicated; this finding might be explained by the relationship status (single vs. stable partnership) of the dreamers. The comparison of large dream samples may shed light on the similarities and differences between the inner worlds of people of different countries and cultures.     

Laterality in Maternal Cradling and Infant Positional Biases: Implications for the Development and Evolution of Hand Preferences in Nonhuman Primates

Left-sided maternal cradling has been widely reported in human populations. In this paper, I review the evidence of laterality in maternal cradling and infant positional biases in non-human primates. The review revealed some evidence of population-left sided cradling in great apes but little consistency in bias was found among Old and New World monkeys. Very little data have been reported in prosimians. I further describe how asymmetries in either maternal cradling or infant positional biases may explain individual and species differences in hand preference.     

Handedness of duplex DNA: role of the glycosydic torsion

Model building studies on helical structures of polynucleotides indicate the glycosydic torsion, χ, and the sugar pucker to be the most important conformational parameters in determining the handedness of the models. Sugar puckers in two typical regions of the pseudorotational space namely, C2′ endo and C3′ endo and the glycosydic torsion in four ranges, namely, anti, high anti, syn and low anti lead to eight conformational combinations for the model bulding of base-paired double helical structures of polynucleotides. Interestingly, not all combinations of sugar pucker and glycosidic torsion lead to structures with Watson-Crick base-pairing. The stereochemical details of the double stranded Watson-Crick base-paired models and their consistency with X-ray diffraction data are discussed.     

Medication and Dreams: Changes in Dream Content After Drug Treatment

This case study examines the effects of sertraline (Zoloft^TM) on the dream content of a young woman with generalized anxiety disorder and panic attacks. The study used the major categories of Hall and Van de Castle's (1966) system of content analysis to compare dream reports before and after drug treatment. Prior to diagnosis and treatment, the dreamer had high levels of aggression and low levels of friendliness in her dreams. The post-medication dreams more closely approximate the female norms. This pilot study suggests a new direction for research on the effects of medication on dream content.     

Hand Preferences for a Haptic Task in Chimpanzees (Pan troglodytes)

We tested the hand preferences of 20 chimpanzees (Pan troglodytes) for a haptic task requiring individuals to search for grapes in an opaque bucket filled with water. We compared these data to the hand preferences displayed by the same chimpanzees during reaching and bimanual feeding tasks. The chimpanzees displayed no significant hand preference for the reaching or bimanual feeding tasks, but exhibited a right-hand preference while performing the haptic task. In contrast, New and Old World monkeys display left-hand preferences for similar tasks. We discuss the relevance of these findings for the evolution of handedness in primates.     

The Home Dreams and Waking Fantasies of Boys and Girls Between Ages 9 and 15: A Longitudinal Study

In this longitudinal developmental study, 12 boys and 12 girls provided home dreams and waking fantasies at 3 age levels: 9–11, 11–13, and 13–15. A total of 299 dreams and 286 fantasies were coded by 2 independent raters using Hall and Van de Castle (1966) content categories. In addition, word counts and bizarreness ratings were completed. There were very few changes in the dreams or waking fantasies of either boys or girls, but dream reports were longer at ages 13–15, the aggression/friendliness percent increased over the course of the study, joint-sex peer groups became more frequent, and girls showed a decline in animal percent. The tendency in a wide range of societies for men to dream mostly about other men and for women to dream equally of women and men was found in both the dreams and waking fantasies. Dreams and fantasies differed markedly, with dreams containing more outdoor and unfamiliar settings, and more bizarreness. In dreams the children tended to portray themselves as victims of aggression and recipients of friendliness, but in fantasies they took a more active role as aggressors and befrienders. It is suggested that the children in this study portrayed themselves in their dreams as they conceived of themselves in everyday life, while in their waking fantasies they imagined themselves as they would have liked to be.     

Handedness in great apes: A review of findings

We present data on hand preference in great apes and discuss them in the context of theoretical models of hand preference in nonhuman primates presented by MacNeilageet al. (1987) and by Fagot and Vauclair (1991). We also discuss several methodological and statistical issues as they pertain to the assessment of hand preference in great apes and other primate species. Finally, we present a comparative framework for the study of hand preference, emphasizing the importance of studies with great apes in developing evolutionary models of hemispheric specialization.     

Factor Analysis of Multiple Measures of Hand Use in Captive Chimpanzees: An Alternative Approach to the Assessment of Handedness in Nonhuman Primates

We tested whether chimpanzee handedness could be characterized as either unidimensional or multidimensional when considered across multiple measures of hand use. We determined for each of 6 different tasks in a sample of 105 captive chimpanzees hand preferences, and subjected the individual hand preference scores to a factor analysis. Five of the 6 tasks loaded on two separate factors that accounted for 54% of the variance. To assess population-level handedness, we calculated handedness indices for the loadings on each factor, for the item loadings across all factors, and for all tasks including ones that did not load on any factor. There is significant population-level right handedness for all 4 indices, which suggests that chimpanzee handedness is multidimensional and not task specific.