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Sex and genetic differences in hair color changes during early childhood.

Hair color was assessed routinely from three months to six years for children participating in a longitudinal study of twins: 169 female twin pairs, 161 male pairs, and 60 opposite-sex pairs. Age trends, established by sampling only one number of every pair, showed marked changes in hair color for both sexes, but there was a consistent excess of light-haired males and dark-haired females. Within-pair concordance rates were calculated for same-sex pairs whose zygosity had been determined independently through bloodtyping. A high rate of concordance was found for MZ twins at every age in spite of the general change in hair color, indicating a strong genetic influence in the timing of color changes. The results are discussed in terms of accelerated maturation of females, and the need for genetic models of the inheritance of hair color which are age- and sex-specific.

Age Factors

[Sex differences in hair color].

The hair-colours of an unselected Vienese sample (8399 male, 8176 female) of all ages and ascertained by the author himself have been analysed with regard to their sexual distribution. The comparisons of the age-groups necessary because of the individual age-changes of the hair-colour did not reveal any significant sexual dimorphism. Only during the periods of intensified growth the girls show a slight tendency to darker hair than the boys at the same age because of their faster development.

Adolescent

Mutagenicity studies on urine concentrates from female users of dark hair color products.

Urines from women, collected before and after hair dyeing, were evaluated for mutagenic activity in the Ames Salmonella-Microsome Test. Thirty (30) sets of samples were tested as concentrates following removal of histidine on an XAD-2 resin column. None of the samples taken following the use of various Clairol products containing high levels of dyes gave any indication of increased mutagenic activity when compared to samples taken before hair dyeing. These results indicate that the use of hair dyes does not result in exposure of the urinary system to mutagens detectable in a sensitive microbial system, and thus suggest the absence of significant biological effects among users of hair dyes and persons occupationally exposed.

Female

Infants' perception of similarity between live people and their photographs.

5-month-old infants who had been habituated to a live face showed no change in fixation time when presented with an immediately following photographic slide of that same face, while they showed an increase in fixation time (dishabituation) to a photographic slide of a novel face of different sex, hair color, and hair style. The similarity in responses to the live person and his photograph indictaes that some identification of people in photographs is possible even in the absence of extended prior developmental experience with pictures. A second experiment found that 5-month-old Ss exhibited the same amount of looking when a live face was followed either by its own photograph or by a photograph of a novel person of like sex, hair color, and hair style. Apparently, these Ss used only rather gross physiognomic features to perceive a similarity between a live person and that person's photograph.

Discrimination, Psychological

Coloring the hair.

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Coloring Agents