Ira B. Perelle

An international study of human handedness: The data

Human handedness has been the subject of systematic study since 1646, but there is no agreement among researchers as to who can be considered a left-hander, what is the etiology of left-handedness, or what the proportion of left-handedness is in the worlds population. This article reports the results of a handedness survey administered to 12,000 subjects in 17 countries, the largest handedness survey attemped. The paper discusses methods for determining handedness, the probability of a genetic component for handedness, and the relationship of sex, birth order, multiple birth, and first-degree relatives handedness on subjects handedness. A hypothesis for the etiology of left-handedness is presented.

Methodologic aspects of sodium appetite: an addendum.

The study was concerned with development of better methods for inducing an abrupt enhancement of sodium appetite. Rats were administered a single subcutaneous injection of the natriuretic drug, furosemide (10 or 20 mg), or the mineralocorticoid hormone, desoxycorticosterone (5 or 10 mg), or a combination of the two substances (10 mg of furosemide and 5 mg of desoxycorticosterone). Intakes of 3% saline, water, and food were measured for 4 days preceding and 4 days following the injections. The most potent natrorexigenic treatments were the high dose of desoxycorticosterone and the combination of furosemide and desoxycorticosterone.

HUMAN HANDEDNESS: THE INFLUENCE OF LEARNING

55 subjects were divided by writing-hand preference and further divided into control and experimental conditions. All subjects were administered a manipulative skill at pretest, counterbalanced for starting hand. Experimental subjects were given 5 practice sessions, and then all subjects were administered a posttest. Posttest scores of both hands of experimental subjects indicated significant improvement as a result of practice, with the nonpreferred hand showing no significant difference from the preferred hand. These findings were related to the etiology of handedness which is hypothesized to involve two factors, one verbal and dichotomous, the other nonverbal and continuous.

What is a lefthander

Attributes of lefthanders and lefthandedness were examined and 3 etiologies of lefthandedness were proposed.

Human handedness and scalp hair whorl direction: no evidence for a common cause.

A much wider variation in many physical and cognitive behaviours exists among left-handers than among right-handers, which is evidence for more than one aetiology of left-handedness. Despite these findings some researchers are still attempting to link left-handedness to a single cause, most recently genetic determination, by pairing left-handedness with a presumed genetically based characteristic. One of these characteristics is scalp hair whorl, which may be clockwise, counter-clockwise (purportedly associated with left-handedness), or a reversal whorl (rare). Results of recent research in this topic are reviewed, our own findings are presented, and we conclude that there is no logical reason for, nor evidence of, a common aetiology of both hair whorl direction and handedness.

ALTERED COMPETITION BETWEEN TWO REPRODUCTIVELY ISOLATED STRAINS OF DROSOPHILA MELANOGASTER

The strains of Drosophila melanogaster studied here are completely infertile when crossed and have been used previously in studies of the evolution of premating sexual isolation (Ehrman, 1971, 1973). Here we investigate competition between larvae of the two strains. Character displacement in the region of sympatry of closely related species (Brown and Wilson, 1956) led us to the working hypothesis that mechanisms to reduce competition would have evolved during the eight years that these strains have been cultured sympatrically. This could be detected through comparison with controls that have been cultured in separate bottles, allopatrically. To our knowledge, this research is the first study of simultaneous evolution of premating sexual isolation and altered competitive response. There is evidence from both intraspecific and interspecific competition studies to indicate that relative pre-adult viabilities vary with larval density (Sang, 1949; Chiang and Hodson, 1950; Lewontin, 1955; and Barker and Podger, 1970), availability of food (Bakker, 1961) and the relative frequency of the competing species or genotypes (Barker and Podger, 1970; Putwain et al., 1967). Additional evidence indicates that the fitness of a particular genotype in a given environment may be improved or impaired by the presence in that same environment of conspecific carriers of other genotypes (Levene et al., 1954; Beard-

Lateral consistency in Drosophila

nights for each bird/treatment). Significance levels refer to Rayleigh tests of these pooled data. In each diagram north is at the top and the radius is equal to the greatest number of activity units in any 15” sector (value given at upper left of each diagram). Dots on the circumference of the circles denote modal directions of birds on single nights with significant directionality. R birds were adults; L birds were immatures. N.A. = no activity. Lateral Consistene~ in Drosophila

Attention to stimulus presentation mode as a function of sex.

This study investigated sex differences in attention to verbal stimuli presented in auditory and visual modes. Ss were 996 male and female students, ages 7 through 17, who observed different forms of a sound motion picture film. One control film contained auditory verbal stimuli only, the other control film contained visual verbal stimuli only, and the experimental film contained simultaneous, conflicting auditory and visual verbal stimuli. Attending behavior was quantified as the number of stimulus specific answers on a paper-and-pencil test administered after presentation of the film. Prior results had indicated that experimental Ss under the age of 12 attended auditory stimuli significantly more often, and those over the age of 13 attended visual stimuli significantly more often. The present experiment concerned sex differences in attending behavior during the crossover period: it was found that females switched their preference for auditory stimuli to visual stimuli earlier (age 11.5) than males (age 13.5). The significant differences between sexes (p less than .05) were attributed to differential conditioning of attitudes, reinforcements, and discriminations regarding the stimulus presentation mode, as well as biological factors.