Factors influencing the selection and rejection of Szondi's pictures: a study of uniovular twins brought up apart

Handedness in twins reared apart: A review of the literature and new data

Reared-apart twin studies are a powerful means for identifying the relative contributions of heredity and environment to variation in human physical and behavioural traits. One such characteristic is handedness, for which it has long been noted that approximately 20% of twin pairs are comprised of one right-handed cotwin and one left-handed cotwin. Reared-together twin studies suggest a slightly greater concordance in monozygotic (MZT) than dizygotic (DZT) twins, implying that genetics influences hand preference. We report here two studies of handedness in reared-apart twins. Study 1 synthesizes the available data and estimates that at least N = 560 same-sex reared-apart twin pairs (for which zygosity is known with reasonable confidence) have been identified. Of these, handedness data are available for both members of n = 415 pairs. We observed similar levels of concordance/discordance for reared-apart monozygotic (MZA) and dizygotic (DZA) twins. However, although direction of handedness (right or left) has frequently been examined, strength of handedness (strong or weak) has not. Study 2 examined strength of hand preference and relative hand skill, as well as right- and left-hand speed, information available for participants in the Minnesota Study of Twins Reared Apart (MISTRA). We provide evidence of heritability for right-hand and left-hand speed. We also found hand preference strength was more alike than chance in DZA, but not MZA, twins. Findings are discussed in relation to genetic and environmental influences on human handedness.

Women and depression

For every male diagnosed as suffering from depression there are two to six females. The reasons for this incidence are examined by looking at diagnostic practices, theories of depression, their validity and applicability to women, and new work which both confirms the high incidence of depression and points to new understanding.

Systems of classification show a striking lack of conceptual clarity. Types of depression are distinguished on the basis of such variables as mood, activity level, severity, presumed genetic or non-genetic origin, and contact with reality. Although ill-defined and misunderstood, nevertheless depression is no myth. Genetic, endocrine, psychodynamic, cognitive, behavioural and social theories of depression all seek to explain the behaviour of the depressed person.

Notwithstanding the relevance, or partial relevance, of some of these theories, there is a major pitfall. The difficulty is typically formulated as a dysfunction of the individual woman, and it is envisaged that treatment should effect some change on her part. The need to change her environment is rarely addressed, her husband seldom included except as a help and support to her, and she is almost never apprised of the role of social structures and her own socialization in creating and perpetuating her distress. New work underscores the difficulties of women's daily experience and its connection to depression. Non-psychiatric women writers, addressing a general audience, have given the best description of women's daily lives and the paths to resentment, misery, frustration, boredom, and fatigue.