Evidence that gonadal hormones during prenatal and neonatal development influence behavior is reviewed. Several theoretical models of hormonal influences, derived from research in other species, are described. These models are evaluated on the basis of data from humans with either normal or abnormal hormonal exposure. It is concluded that the evidence is insufficient to determine which model best explains the data. Sexual differentiation may involve several dimensions, and different models may apply to different behaviors. Gonadal hormones appear to influence development of some human behaviors that show sex differences. The evidence is strongest for childhood play behavior and is relatively strong for sexual orientation and tendencies toward aggression. Also, high levels of hormones do not enhance intelligence, although a minimum level may be needed for optimal development of some cognitive processes. Directions for future research are proposed.
"The process of puberty results in the release of some specific hormones which are primarily responsible for the development of secondary sex characteristics and for the emergence of reproductive capabilities in boys . During this stage an increase in testosterone causes an increase in the sex drive (libido), enlargement of the reproductive organs such as the penis and testes, the production of sperm, increase of muscle mass and lowering of the voice, increased frequency of erection, and the growth of facial, chest, nipple and pubic hair among boys . "
[Show abstract][Hide abstract] ABSTRACT: The use of crude kerosene as a dietary supplement in boarding schools has been a common practice in east Africa and other countries for many years, with the belief of it reducing the sex drive (libido) at the pubertal stage. There is however no scientific basis for this belief. The present study aimed at using a rat animal model to investigate the effects of crude kerosene on serum testosterone levels, aggression and its possible toxic effects. Fifteen male albino rats of approximately similar age and average weights were put into three groups of five animals each; the control group (placebo), low kerosene dose (10 μl/day) group and high kerosene dose (300 μl/day) group. ELISA was used to determine the serum testosterone levels. During treatment, changes in aggression were observed and noted. Liver toxicity was determined using enzyme assays, total protein and albumin while renal toxicity was monitored using serum creatinine levels. A full hemogram was conducted to determine hematological effects. Various tissue biopsies were obtained and examined using histopathological techniques for evidence of toxicity. Contrary to the common belief, our findings showed an overall increase of serum testosterone levels of up to 66% in the low dose and 75% in the high dose groups, with an increasing trend by the end of the study. The high dose group showed significantly increased levels of white blood cells (WBC) (p = 0.036), red blood cells (RBC) (p = 0.025), hematocrit (HCT) (p = 0.03), red cell distribution width (p = 0.028) and platelets (p = 0.017). The histological results of the stomach indicated chronic gastritis.
"The origin and scope of psychological gender differences are some of the most challenging and fascinating questions for both social and cognitive psychologists, and require interdisciplinary investigations that go beyond simple contrasts between the genders (Eagly and Wood, 1999; Wood and Eagly, 2002). For cognitive psychologists, the innate biological differences such as steroidal gonadal hormone difference (e.g., Hines, 1982; Collaer and Hines, 1995), genetic disparity (e.g., Heath et al., 1999), and cognitive ability gap (e.g., Hyde and Linn, 1988; Miller and Halpern, 2014) reportedly contribute to the differences found between females and males. Social psychologists, on the other hand, tend to focus on social construction explanations, where the importance of societal role differentiations for females and males (e.g., Bohan, 1993) provides an explanation for observed discrepancies between the two genders. "
[Show abstract][Hide abstract] ABSTRACT: In this study, we investigated whether the first impression of a crowd of faces-crowd perception-is influenced by social background and cognitive processing. Specifically, we explored whether males and females, two groups that are distinct biologically and socially, differ in their ability to extract ensemble characteristics from crowds of faces that were comprised of different identities. Participants were presented with crowds of similar faces and were instructed to scroll through a morphed continuum of faces until they found a face that was representative of the average identity of each crowd. Consistent with previous research, females were more precise in single face perception. Furthermore, the results showed that females were generally more accurate in estimating the average identity of a crowd. However, the correlation between single face discrimination and crowd averaging differed between males and females. Specifically, male subjects' ensemble integration slightly compensated for their poor single face perception; their performance on the crowd perception task was not as poor as would be expected from their single face discrimination ability. Overall, the results suggest that group perception is not an isolated or uniform cognitive mechanism, but rather one that interacts with biological and social processes.
Frontiers in Psychology 09/2015; 6:1300. DOI:10.3389/fpsyg.2015.01300 · 2.80 Impact Factor
"Deleterious mutations in AR can result in syndromes ranging from mild abnormalities to total failure of normal male phenotypic development (McPhaul, 2002a,b). AR also has associations with disease states (such as prostate cancer) and behavior in humans (Collaer and Hines, 1995; Wyce et al., 2010; Zitzmann and Nieschlag, 2003). Androgen receptors (AR) are DNA-binding transcription factors, the main regulators of androgen signaling in the cell, activated mostly by testosterone and 5α-dihydrotestosterone. "
[Show abstract][Hide abstract] ABSTRACT: Androgen receptor genes (AR) have been found to have associations with reproductive development, behavioral traits, and disorders in humans. However, the influence of similar genetic effects on the behavior of other animals is scarce. We examined the loci AR glutamine repeat (ARQ) in 44 Grevy's zebras, 23 plains zebras, and three mountain zebras, and compared them with those of domesticated horses. We observed polymorphism among zebra species and between zebra and horse. As androgens such as testosterone influence aggressiveness, AR polymorphism among equid species may be associated with differences in levels of aggression and tameness. Our findings indicate that it would be useful to conduct further studies focusing on the potential association between AR and personality traits, and to understand domestication of equid species.
Meta Gene 09/2015; 5:120-123. DOI:10.1016/j.mgene.2015.06.006
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