On the evolution of handedness: a speculative analysis of Darwin's views and a review of early studies of handedness in "the nearest allies of man"

Scientists today who seek clues into the evolutionary origins of human handedness make extensive use of evidence from comparative studies, that is, studies that ask whether handedness occurs in other species, especially apes and monkeys, as the Darwinian principle of continuity would seem to imply, or whether it is uniquely human. Early investigations had the same goal and drew on much the same kind of evidence. In this article, I review studies of animal handedness in the period before 1859, when Darwin published On the Origin of Species, and afterward, through the 1st decade of the 20th century. Inasmuch as Darwin's published writings contain hardly any statements about handedness and none at all about its evolution and continuity across species, I also speculate about what Darwin himself might have said on the subject. To do this, I draw on his statements on related matters, such as the form and structure of the hand and the transition from a quadrupedal to bipedal stance, on other writers' reports and opinions about handedness with which he was familiar or likely to have been familiar, and finally, on clues from his own and only statement about animal handedness in an unpublished letter. I conclude by asking whether and how early investigators, lacking any statement by Darwin on the evolution of handedness, invoked his theory of evolution and his views on related matters in the interpretation of their findings.     

Unwanted and unfollowed: Defining ghosting and the role of social media unfollowing

Ghosting involves terminating communication, including through technological mediums, as a means of ending a relationship. Despite attention from popular media, empirical examinations of this breakup strategy are sparse. Using a correlational design, we examined the defining features of ghosting including its associations with other breakup tactics, whether it is an exclusively unilateral strategy, and the role of social media unfollowing in its implementation. A convenience sample of primarily undergraduate students (n = 260) completed an online survey describing recent breakups, indicating the disengagement tactics used, social media unfollowing, and the extent to which the breakups involved ghosting. Findings indicated that ghosting is extremely common, it was used to terminate more than half of participants' recent relationships. Most participants had experienced a breakup involving ghosting as either the disengager and/or the recipient. Ghosting was found to involve less open confrontation, more avoidance/withdrawal and de-escalation tactics. Contrary to previous research, ghosting can occur bilaterally, with partners ghosting each other. Social media unfollowing is an important aspect of ghosting. Relationships ended via ghosting have fewer post-breakup connections than those ended through other strategies. Typically, ghosters initiate social media unfollowing. Findings provide insight into how ghosting should be conceptualized and measured in future explorations.     

Deception by young children following noncompliance

A paradigm devised by M. Lewis, C. Stanger, and M. W. Sullivan (1989) was adapted to study deception and false-belief understanding. In Study 1, 3- and 5-year-olds were asked not to touch a toy in the experimenter's absence. Just over half of the children touched the toy, and of those children, the majority denied having done so. Of control children who were given permission to touch the toy, all touched it and admitted having done so. In Study 2, 3- and 5-year-olds were asked not to look in a box to identify its contents. Almost all children looked, most denied having looked, and a minority consistently feigned ignorance of the contents. False-belief understanding was linked to denial of looking but not to feigning ignorance. Of control children who were given permission to look, all acknowledged looking, and they almost always revealed their knowledge of the contents. The studies confirm that preschoolers deceive in the context of a minor misdemeanor but are less effective at feigning ignorance.     

Physical Attractiveness and Psychological Adjustment Among Substance Abuse Inpatients: A Longitudinal Study1

Relations between psychological adjustment and physical attractiveness were examined longitudinally in substance abuse inpatients, controlling for the effects of length of drug abuse, length of inpatient stay, age, and socioeconomic status. Measures of adjustment and attractiveness were obtained during the first week of admission and six weeks later (within two weeks of discharge). Regression analyses indicated that initial attractiveness did not predict later adjustment, and initial adjustment did not predict later attractiveness. Partial correlation analyses revealed a positive association between attractiveness and adjustment at the first time point, but not at the later time point. These results suggest that physical attractiveness exerts only a temporary effect on judgments of adjustment in an inpatient setting. Attractiveness may affect decisions made when screening patients at mental health facilities, but may not affect decisions made over the full course of inpatient treatment.     

An empirical approach to the classification and treatment of maximum security psychiatric patients

Treatment approaches with forensic patients have traditionally been nonspecific and have been based primarily on legal or diagnostic categories. The current study, stimulated by the need to reorganize treatment and assessment services, examined the incidence among 189 maximum security psychiatric patients of 70 problems commonly exhibited either in the community prior to admission or within the institution. Through a series of factor and cluster analyses, a model for the placement and treatment of these patients was developed that included assaultiveness, level of functioning, social withdrawal, and active psychotic symptoms.     

A further examination of the constructs underlying assessment center ratings

Previous factor analytic work (Sackett and Dreher, 1982) has found exercise factors, rather than the expected dimension factors, underlying ratings made in managerial assessment centers. The present paper responds to criticisms that inappropriate analyses were conducted and that unrepresentative assessment centers were studied. Exercise factors were found to predominate in two new sets of assessment data which we obtained and in three studies published by other authors, thus indicating that the results were not idiosyncratic to the three centers studied by Sackett and Dreher. Analyses using confirmatory, rather than exploratory, factor analysis also support the dominance of exercise factors. Although dimension factors were found in three of four data sets studied, variables loading on a dimension factor consistently loaded more highly on an exercise factor as well.     

Exposure effects on the psychophysical scaling methods of magnitude estimation and cross-modal matching for vibrotactile stimulation of the tongue and hand

The purpose of the present study was to investigate possible effects of exposure upon psychophysical scaling responses when vibrotactile magnitude estimation and cross-modal matching are conducted within the same experiment. Four groups of 10 subjects each, with an over-all age range of 18-23 yr., were employed. Groups 1 and 2 performed magnitude estimation for lingual vibrotaction and cross-modal matching with the lingual vibrotactile stimulus as the standard. Group 1 received the magnitude-estimation task first and Group 2 received the cross-modal-matching task first. Groups 3 and 4 performed magnitude estimation for vibrotaction applied to the thenar eminence of the hand and cross-modal matching with the vibrotactile stimulus applied to the thenar eminence of the hand as the standard. Group 3 received the magnitude-estimation task first and Group 4 received the cross-modal-matching task first. The psychophysical scaling methods of magnitude estimation and cross-modal matching showed very little exposure effect of one upon the other when used in the same experiment. Also, magnitude scaling responses tended to increase more rapidly with increases in vibrotactile stimulus intensity when the test site was the thenar eminence of the hand as opposed to the dorsum of the tongue.