Digit Ratio 2D:4D,facial masculinization and aggressiveness in Spanish adolescents / Índice 2D:4D,masculinización facial y agresividad en adolescentes españoles

Abstract

This study aims to test whether two morphometric characteristics, the second to fourth finger length ratio (2D:4D index) and the facial width-to-height ratio (FWH index), which reflects the degree of facial masculinization, are related to aggression in adolescents of both sexes. Previous studies have proposed that the 2D:4D index (a trait related to prenatal testosterone) and the FWH (related to testosterone during puberty) are related to aggressiveness in adult males (although there is evidence to the contrary). In the present study we investigate the relationship of both traits with different measures of aggression in a mixed population of 296 adolescents (14–19 years old). We did not find relationships between 2D:4D and FWH with aggressiveness. Furthermore, our results suggest that the FWH index must be used only after controlling for body mass index.     

Neuroprotective Effects of Testosterone on Regenerating Spinal Cord Motoneurons in Rats

Degeneration in the CNS and peripheral nervous system consists of degradation and phagocytosis of axons and their myelin sheath distal to the site of injury. Testosterone is a gonadal sex steroid hormone that plays an important role in CNS development. One of the lesser-known testosterone actions is neuroprotection. In the present study, the authors investigated the neuroprotectective effect of intracerebral ventricular injection of testosterone on the number of spinal motoneurons after sciatic nerve crush. In all, 32 male Wistar rats were divided to 4 groups (control, compression, compression + castration, compression + testosterone injections; n = 8). Four weeks after compression the lumber segments of spinal cord were sampled, processed, sectioned serially, and stained with toluidine blue (pH = 4.65) by using steriological quantitative technique (physical dissector), the number of alpha motoneurons in the right ventral horns of spinal cord were counted and compared between groups. Statistical analyses showed that testosterone injections (1μl icv, 4 times, 1 week interval between injections) significantly (p < .05) reduced neuronal damage. These results indicated that testosterone has an obvious neuroprotective effect on lumbar spinal motoneurons.     

Lack of correlation between digit ratio (2D:4D) and Baron-Cohen’s “Reading the Mind in the Eyes” test, empathy, systemising, and autism-spectrum quotients in a general population sample

The second-to-fourth digit ratio (2D:4D) is sexually differentiated and is a likely biomarker for the organisational (permanent) effects of prenatal testosterone on the human brain. Recent research has highlighted a possible role of prenatal testosterone levels in both the etiology of autism-spectrum disorders and in sex and individual differences in cognitive styles of the normal mind (Baron-Cohen’s Extreme Male Brain Theory of Autism and Empathising/Systemising Theory). Importantly, autistic children present lower (hypermasculinised) 2D:4D than healthy controls. Based on these accounts, we investigated the relation of 2D:4D with Baron-Cohen’s measures of empathising (“Reading the Mind in the Eyes” test, RMET; Empathy Quotient, EQ), systemising (Systemising Quotient, SQ), and autistic-like traits (Autism-Spectrum Quotient, AQ) in the general population (N = 423 Austrian adults). Whereas sex differences into the expected direction and of expected size were obtained for all variables and internal scale consistencies tallied to retrievable reference values, 2D:4D was unrelated to RMET, EQ, SQ, and AQ scores. Candidate explanations for this lack of correlation might be possible developmental timing differences in the expression of 2D:4D and empathising/systemising, qualitative (as opposed to quantitative) functional differences between the normal and the autistic mind, or the suboptimal psychometric properties of the measures.     

Hormonal changes after competition predict sex‐differentiated decision‐making

Recent neuroendocrinology research has pointed out that testosterone (T) and cortisol (C) changes after social interactions can predict risk‐taking behavior in decision‐making, depending on the sex of participants. However, previous research has focused on the effects of the changes in only one hormone, rather than the interaction between them, even though C can suppress T activity. Our aim was to test, in men and women, the role of T changes moderated by C changes after competition in decision‐making. Thus, 48 males and 46 females completed the Iowa Gambling Task (IGT) after a laboratory competition or a noncompetitive task (control task). Saliva samples were collected before and after the competition/control task. IGT was employed to measure risk‐taking decision‐making, considering the degree of uncertainty. Our results showed sex‐differentiated effects of T and C changes on risk‐taking behavior. On the one hand, men from both task groups (Competition/Control) who had higher C and T changes after competition showed more risk‐taking decision‐making (higher IG Risk). On the other hand, women from the competitive task who had high C and T showed conservative decision‐making. Therefore, these results show sex‐differentiated decision‐making profiles, which would help to understand how men and women behave after experiencing a competitive social context.     

Serum cortisol,testosterone, and testosterone-binding globulin responses to competitive fighting in human males

Levels of circulating cortisol, testosterone, and testosterone-binding globulin were measured in 15 male wrestlers in relation to wrestling bouts and their outcomes. Concentrations of cortisol and testosterone increased consistently during wrestling bouts, while levels of testosterone-binding globulin dropped. Winners of competive matches showed greater increases in both cortisol and testosterone than losers. These findings indicate that humans, like other social mammals, may undergo specific endocrine changes in response to victory or defeat.     

Inter-male aggression in mice: Influence of gonadectomy and prior fighting experience

Groups of adult male mice of the Rockland-Swiss strain were paired 0, 2, 7, or 15 times with adult male stimulus animals rendered non-aggressive by extirpation of olfactory bulbs. All animals were castrated and tested until fighting ceased, following which each was given testosterone replacement and tested until fighting was reinstated. More than 50% of mice with no pre-castration fighting experience fought following gonadectomy. Castrated animals permitted 15 pre-castration pairings fought significantly longer than did animals of any of the other treatment groups. Finally, there was no difference among the groups with regard to the latency to resume fighting following the commencement of testosterone replacement. It is concluded that fighting experience enhances the persistence of the behavior following castration.     

Gonadal hormones and intrasexual aggressive behavior in female bank voles (Clethrionomys glareolus)

The effects of gonadal hormones on aggressive behavior in the female bank vole was investigated in 10 min home cage tests. Ovariectomized (ovx) or intact females injected with oil, with progesterone (P), with a mixture of progesterone and estrogen (P+E), or with testosterone (T) alone were confronted in a resident-intruder test with unfamiliar, nonoperated females as intruders. Intact females showed aggressive behavior more frequently than ovx females. Ovx females injected with P, with P+E, or with T made significantly more attacks, and these attacks lasted longer than those observed for oil-treated voles. The results indicate that P, the typical female hormone, is responsible for aggressive behavior in female bank voles; however, only T increased the duration of interfemale aggression. Aggr. Behav. 24:63–70, 1998. © 1998 Wiley-Liss, Inc.     

Agonistic behavior,plasma testosterone,and hypothalamic estradiol binding in male rabbits

The purpose of this study was to establish a relation between agonistic behavior, gonadal hormones, and their receptorial capacity at the central level. Male rabbits were observed in seminatural conditions and three components of their agonistic behavior were recorded: follow, attack, and chase. The three behaviors were mutually correlated and clearly differed among the four members of each group. Within the social group, one rabbit was agonistically more active than the others and his supremacy was associated with an increased level of peripheral testosterone and higher estradiol binding in the hypothalamus. On the whole, the values of the hypothalamic estradiol binding were positively correlated with the behaviors. The results show that, in the male rabbit, agonistic activity is associated with changes in testosterone concentration and in the binding at the central level of its aromatized metabolite estradiol. Aggr. Behav. 23:33–40, 1997. © 1997 Wiley-Liss, Inc.     

Aggression and testosterone: Testing a bio-social model

Based upon reports of a positive correlation between circulating testosterone levels and aggression, we draw upon evolutionary psychology to place the action of testosterone in a broader perspective. We propose that testosterone affects competitive status-seeking and that under certain circumstances (including youth) this is expressed as aggression. Involvement in aggression in turn is associated with adherence to an instrumental social representation of aggression which justifies aggression as a means of imposing control over others and increasing self-esteem. Measures of salivary testosterone, masculinity, preferred social representation of aggression, and multiple aggression scales were collected from an undergraduate sample of 119 men. An Aggression factor was derived from principle components analysis of the aggression measures. The strongest correlates of Aggression were holding an instrumental social representation of aggression and youth. Testosterone showed no significant relationship to the single or aggregate measures of aggression or to any of the other psychometric measures. We suggest ways in which previous work may have over-estimated the strength of the association between circulating testosterone and aggression and discuss the possible relationships between age, social representation, and aggression. Aggr. Behav. 23:239–238, 1997. © 1997 Wiley-Liss, Inc.