In support of 2D:4D: More data exploring its conflicting results on handedness, sexual orientation and sex differences.

In the last few years, several studies have questioned the value of the second-to-fourth digit ratio (2D:4D) as a measure of exposure to sex hormones before birth. Controversy has also extended to the 2D:4D association with individual features previously related to this exposure such as handedness and sexual orientation. Given that it has been argued that sex differences in 2D:4D could be a consequence of body-size differences, we have tested in a large sample the allometric relationship between finger lengths and body size. Our results show that the association is either allometric or isometric, depending on the analyses performed. In any case, the deviation from isometry is not large enough to explain the typically observed sex difference in this trait. We have also tested the association between sexual orientation and 2D:4D, finding a relationship between 2D:4D and sexual orientation in men but not in women. We attribute this discordance with previously published meta-analysis to differences in genetic background, a variable that has gained relevance in recent years in studies involving 2D:4D. Finally, we did not find any relationship between 2D:4D and handedness, evaluated through self-reported preference and hand performance. Our main conclusion is that 2D:4D shows differences between sexes beyond their disparity in body size. In our opinion, 2D:4D can be used cautiously as an indicator of intrauterine exposure to sex hormones taking into account some considerations, such as analysing a very large sample and taking careful measurements of the ethnicity of the sample.

The elusive transcriptional memory trace.

Memory is the brain faculty to store and remember information. It is a sequential process in which four different phases can be distinguished: encoding or learning, consolidation, storage and reactivation. Since the discovery of the first Drosophila gene essential for memory formation in 1976, our knowledge of its mechanisms has progressed greatly. The current view considers the existence of engrams, ensembles of neuronal populations whose activity is temporally coordinated and represents the minimal correlate of experience in brain circuits. In order to form and maintain the engram, protein synthesis and, probably, specific transcriptional program(s) is required. The immediate early gene response during learning process has been extensively studied. However, a detailed description of the transcriptional response for later memory phases was technically challenging. Recent advances in transcriptomics have allowed us to tackle this biological problem. This review summarizes recent findings in this field, and discusses whether or not it is possible to identify a transcriptional trace for memory.

Masculinity and Lying.

Dishonesty in communication has important economic implications. The standing literature has shown that lying is less pervasive than predicted by standard economic theory. We explore whether biology can help to explain this behavior. In a sample of men, we study whether masculine traits are related to (dis)honesty in a sender-receiver game. We study three masculine physical traits: the second-to-fourth digit ratio, facial morphometric masculinity and the facial width-to-height ratio. These biomarkers display significant associations with lying and deception in the game. We also explore the extent to which these effects operate through social preferences or through beliefs about the behavior of receivers.

To which world regions does the valence-dominance model of social perception apply?

Over the past 10 years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgements of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions, we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods and correlate and rotate the dimension reduction solution. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 5 November 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.7611443.v1 .

Men's Bodily Attractiveness: Muscles as Fitness Indicators.

Bodily attractiveness is an important component of mate value. Musculature-a crucial component of men's bodily attractiveness-provides women with probabilistic information regarding a potential mate's quality. Overall musculature is comprised of several muscle groups, each of which varies in information value; different muscles should be weighted differently by attractiveness-assessment adaptations as a result. In the current study, women and men ( N = 1,742) reported size preferences for 14 major muscle groups. Women's reported preferences provided only partial support for our hypotheses that women will prefer muscles that most reliably differentiate between potential mates to be larger; men tended to prefer larger upper-body muscles. We discuss possible interpretations of these mixed findings. Ultimately, our findings suggest that attractiveness-assessment adaptations are sensitive to the information contained within specific muscle groups and they highlight the potential for additional research on the nuances of bodily attractiveness assessment.

Sex Affects the Relationship Between Third Party Punishment and Cooperation.

Prosocial third-party punishment (3PP) is a punitive behavior against antisocial individuals, which might explain extended cooperativeness in humans. 3PP shows sexual dimorphism, being more frequent in men than in women. We studied whether sexually dimorphic features related to sexual hormones during development (facial dimorphism and 2D:4D) influence the tendency to engage in 3PP in a sample of 511 women and 328 men. After playing a Prisoner's Dilemma, participants had to decide whether to penalize the defection of a third player who had exploited his/her counterpart's cooperation. In line with previous studies, we observe that men are more prone to engage in 3PP than women. We find that this sex difference is due to cooperative men being more likely to punish than cooperative women. In addition, men with higher facial masculinity are less likely to engage in 3PP, whereas no features influence 3PP in women. We discuss the possibility that sex differences in the motivations and fitness implications underlying 3PP might be driving the observed results.

Diferencias en la conducta de emparejamiento entre mujeres jóvenes universitarias de Santiago de Chile en relación con el consumo de píldoras anticonceptivas orales / Differences in mating behavior among university young women of Santiago de Chile in relation to the consumption of oral contraceptive pills

Durante los últimos años en Chile se ha detectado una masificación en el uso de anticonceptivos orales. Sin embargo, en Chile y al igual que en casi todos los países latinoamericanos prácticamente no se han investigado sus implicancias sobre la conducta humana. Específicamente, este estudio evaluó el impacto del uso de estos anticonceptivos sobre la conducta de emparejamiento en un grupo de 164 mujeres jóvenes universitarias, con una media de edad igual a 19 años y provenientes de cuatro universidades chilenas. Para ello se utilizó la adaptación chilena del Cuestionario de Componentes del Valor de Pareja que está compuesto por 22 ítems que se responden en una escala Likert de siete valores. Los resultados señalan diferencias entre las mujeres que consumen píldoras anticonceptivas (PA) y las que no lo hacen. Las consumidoras presentan los mayores valores del índice general del cuestionario sobre los componentes del valor de pareja y las subescalas de historia de relaciones de pareja, apreciación desde el sexo opuesto y apariencia. Estos resultados indican que las mujeres consumidoras de la PA se autoperciben y creen que el sexo contrario las evalúa como atractivas y muestran una vida sexual más diversificada, no mostrando diferencias en los otros aspectos relevantes para el valor de pareja no vinculados centralmente al atractivo físico. En definitiva, los resultados parecen indicar que el consumo de anticonceptivos hormonales no modifica la conducta social y parental de las mujeres, aunque su uso parece estar asociado con una mayor autopercepción de atractivo y mayor diversidad sexual.

Oral contraceptives, also known as birth control pills (PAs from now on), have been available on the world market for five decades. At present, the use of PA is massifier worldwide, being consumed by more than 100 million women on the planet. In recent years, in Latin America has been detected a dramatic increase in the use of oral contraceptives, and Chile is not the exception. In this sense, it is probable that the increase in the consumption of PAs in Chile is linked to the increase of women who decide to pursue higher studies and to develop professional careers. Concurrently, a wide field of research has been focused on the physiological and psychological effect of the consumption of oral contraceptives on human behavior, being mating behavior one of the main topics of research. However, in Chile as in most Latin American countries there is a lack of studies on the implications of the consumption of oral contraceptives on human behavior. In the present study, we investigated in a group of 164 university young women (Mean ± Standard Deviation: 19.27± 2.88 years) of Chile the impact of the use of oral contraceptives on mating behavior. Accordingly, we have applied a validated psychometric test to assessed mate value, one of the more relevant components of mating behavior i.e., the Mate Value Questionnaire. Mate value can be defined as a construct that incorporates a number of physical, psychological, and social dimensions that are related to an individual's ability to find, attract, and successfully retain a partner. This questionnaire is composed by 22 items and 7 subscales that are answered in a Likert Scale of 7 values. The Mate Value Questionnaire showed a high reliability (α = .85). According with previous studies that showed a decrease in sexual satisfaction and desire on women that consume oral contraceptives, we predicted a decrease of mating behavior and, then, a decrease on Mate Value for those women that use oral contraceptives. This effect was expected for all subscales of this questionnaire with the exception of relationship history subscale since women that consume oral contraceptives reported to have more diverse sexual partners on previous studies. The results show differences between women who use oral contraceptives (n = 87 women: 19.60 ± 2.89 years) in comparison to those who do not (n = women: 18.90 ± 2.84 years). However, the differences were, in general, opposed to our expectations being the consumers of oral contraceptives who presented the highest values of the general index of the Mate Value Questionnaire, and, concretely, for the subscales of relationship history, views of the opposite sex, and looks. In addition, we have failed into found any differences between groups in subscales that were not associated to physical appearance, such as wealth, sociality and fear of failure. The results suggest that the use of hormonal contraceptives does not modify the social and parental behavior of the women, although their use seems to be associated with a greater self-perception of attractiveness and greater diversity in sexual life. This study provides new information that will increase the understanding and discussion about the hypothetical effect that would or would not, the consumption of the PA on the pairing behavior. It is important to point out that the field of research on changes in the sexual preferences of women, derived from hormonal states, is in an important discussion process. Therefore, we believe that it is critical to carry out research in the future in order to elucidate the real robustness of this phenomenon, improving our understanding about the behavioral effects of consuming oral contraceptives.

Presynaptic Aß40 prevents synapse addition in the adult Drosophila neuromuscular junction.

Complexity in the processing of the Amyloid Precursor Protein, which generates a mixture of ßamyloid peptides, lies beneath the difficulty in understanding the etiology of Alzheimer's disease. Moreover, whether Aß peptides have any physiological role in neurons is an unresolved question. By expressing single, defined Aß peptides in Drosophila, specific effects can be discriminated in vivo. Here, we show that in the adult neuromuscular junction (NMJ), presynaptic expression of Aß40 hinders the synaptic addition that normally occurs in adults, yielding NMJs with an invariable number of active zones at all ages tested. A similar trend is observed for Aß42 at young ages, but net synaptic loss occurs at older ages in NMJs expressing this amyloid species. In contrast, Aß42arc produces net synaptic loss at all ages tested, although age-dependent synaptic variations are maintained. Inhibition of the PI3K synaptogenic pathway may mediate some of these effects, because western analyses show that Aß peptides block activation of this pathway, and Aß species-specific synaptotoxic effects persists in NMJs overgrown by over-expression of PI3K. Finally, individual Aß effects are also observed when toxicity is examined by quantifying neurodegeneration and survival. Our results suggest a physiological effect of Aß40 in synaptic plasticity, and imply different toxic mechanisms for each peptide species.

Facial Features: What Women Perceive as Attractive and What Men Consider Attractive.

Attractiveness plays an important role in social exchange and in the ability to attract potential mates, especially for women. Several facial traits have been described as reliable indicators of attractiveness in women, but very few studies consider the influence of several measurements simultaneously. In addition, most studies consider just one of two assessments to directly measure attractiveness: either self-evaluation or men's ratings. We explored the relationship between these two estimators of attractiveness and a set of facial traits in a sample of 266 young Spanish women. These traits are: facial fluctuating asymmetry, facial averageness, facial sexual dimorphism, and facial maturity. We made use of the advantage of having recently developed methodologies that enabled us to measure these variables in real faces. We also controlled for three other widely used variables: age, body mass index and waist-to-hip ratio. The inclusion of many different variables allowed us to detect any possible interaction between the features described that could affect attractiveness perception. Our results show that facial fluctuating asymmetry is related both to self-perceived and male-rated attractiveness. Other facial traits are related only to one direct attractiveness measurement: facial averageness and facial maturity only affect men's ratings. Unmodified faces are closer to natural stimuli than are manipulated photographs, and therefore our results support the importance of employing unmodified faces to analyse the factors affecting attractiveness. We also discuss the relatively low equivalence between self-perceived and male-rated attractiveness and how various anthropometric traits are relevant to them in different ways. Finally, we highlight the need to perform integrated-variable studies to fully understand female attractiveness.

Facial masculinity: how the choice of measurement method enables to detect its influence on behaviour.

Recent research has explored the relationship between facial masculinity, human male behaviour and males' perceived features (i.e. attractiveness). The methods of measurement of facial masculinity employed in the literature are quite diverse. In the present paper, we use several methods of measuring facial masculinity to study the effect of this feature on risk attitudes and trustworthiness. We employ two strategic interactions to measure these two traits, a first-price auction and a trust game. We find that facial width-to-height ratio is the best predictor of trustworthiness, and that measures of masculinity which use Geometric Morphometrics are the best suited to link masculinity and bidding behaviour. However, we observe that the link between masculinity and bidding in the first-price auction might be driven by competitiveness and not by risk aversion only. Finally, we test the relationship between facial measures of masculinity and perceived masculinity. As a conclusion, we suggest that researchers in the field should measure masculinity using one of these methods in order to obtain comparable results. We also encourage researchers to revise the existing literature on this topic following these measurement methods.

Changes in preference for male faces during the menstrual cycle in a Spanish population / Cambios en la preferencia por rostros masculinos durante el ciclo menstrual en población española

A recent and controversial hypothesis suggests the presence of an oestrus phase in women as in other mammals. This implies that women at their optimal fertility point of the menstrual cycle exhibit behaviors focused to maximize the genetic quality of their offspring. Several studies support this hypothesis, finding that women in the fertile phase tend to prefer men with traits associated to phenotypic quality, such as greater facial masculinization and symmetry. We experimentally tested some of the observations supporting this hypothesis in a population of 810 young Spanish women. We analyzed whether the preference for masculinized male faces is affected by I) the phase of the menstrual cycle, II) having a stable partner and III) the use of birth control pills. We could not repro-duce the effect of the first two factors, but we found that women using hormonal contraceptives tend to prefer men with less masculine faces. These results indicate that some of the evidences supporting the oestrus hypothesis in humans must be reviewed, incorporating data from different socio-cultural and ethnic populations

Recientemente se ha postulado una controvertida hipótesis que propone la presencia de un periodo de estro en las mujeres, como ocurre en otros mamíferos. Ello implica que las mujeres en el óptimo de fertilidad del ciclo menstrual presenten comportamientos encaminados a maximizar la calidad genética de su descendencia. Diversas investigaciones sostienen esta hipótesis, al encontrar que las mujeres en la fase fértil prefieren hombres con rasgos que denotan mayor calidad fenotípica, como un mayor grado de masculinización o una mayor simetría. Nuestro objetivo ha sido testar experimentalmente en una población de 810 jóvenes españolas alguna de estas observaciones. Analizamos si, tal como se recoge en la bibliografía, la preferencia por rostros de hombres masculinizados se ve afectada por I) la etapa del ciclo menstrual, II) el tener pareja estable y III) el empleo anticonceptivos hormonales. No hemos podido reproducir el efecto de los dos primeros factores, pero sí encontramos que las mujeres que emplean anticonceptivos hormonales prefirieron rostros de hombre menos masculinos. Estos resultados no refutan la hipótesis del estro en humanos, pero nos indican que algunas de las pruebas que la sustentan han de ser reconsideradas, incorporando datos de poblaciones étnica y socioculturalmente diferentes

The extracellular matrix protein artichoke is required for integrity of ciliated mechanosensory and chemosensory organs in Drosophila embryos.

Sensory cilia are often encapsulated by an extracellular matrix (ECM). In Caenorhabditis elegans, Drosophila melanogaster, and vertebrates, this ECM is thought to be directly involved in ciliary mechanosensing by coupling external forces to the ciliary membrane. Drosophila mechano- and chemosensory cilia are both associated with an ECM, indicating that the ECM may have additional roles that go beyond mechanosensory cilium function. Here, we identify Artichoke (ATK), an evolutionarily conserved leucine-rich repeat ECM protein that is required for normal morphogenesis and function of ciliated sensilla in Drosophila. atk is transiently expressed in accessory cells in all ciliated sensory organs during their late embryonic development. Antibody stainings show ATK protein in the ECM that surrounds sensory cilia. Loss of ATK protein in atk null mutants leads to cilium deformation and disorientation in chordotonal organs, apparently without uncoupling the cilia from the ECM, and consequently to locomotion defects. Moreover, impaired chemotaxis in atk mutant larvae suggests that, based on ATK protein localization, the ECM is also crucial for the correct assembly of chemosensory receptors. In addition to defining a novel ECM component, our findings show the importance of ECM integrity for the proper morphogenesis of ciliated organs in different sensory modalities.

Klumpfuss controls FMRFamide expression by enabling BMP signaling within the NB5-6 lineage.

A number of transcription factors that are expressed within most, if not all, embryonic neuroblast (NB) lineages participate in neural subtype specification. Some have been extensively studied in several NB lineages (e.g. components of the temporal gene cascade) whereas others only within specific NB lineages. To what extent they function in other lineages remains unknown. Klumpfuss (Klu), the Drosophila ortholog of the mammalian Wilms tumor 1 (WT1) protein, is one such transcription factor. Studies in the NB4-2 lineage have suggested that Klu functions to ensure that the two ganglion mother cells (GMCs) in this embryonic NB lineage acquire different fates. Owing to limited lineage marker availability, these observations were made only for the NB4-2 lineage. Recent findings reveal that Klu is necessary for larval neuroblast growth and self-renewal. We have extended the study of Klu to the well-known embryonic NB5-6T lineage and describe a novel role for Klu in the Drosophila embryonic CNS. Our results demonstrate that Klu is expressed specifically in the postmitotic Ap4/FMRFa neuron, promoting its differentiation through the initiation of BMP signaling. Our findings indicate a pleiotropic function of Klu in Ap cluster specification in general and particularly in Ap4 neuron differentiation, indicating that Klu is a multitasking transcription factor. Finally, our studies indicate that a transitory downregulation of klu is crucial for the specification of the Ap4/FMRFa neuron. Similar to WT1, klu seems to have either self-renewal or differentiation-promoting functions, depending on the developmental context.

Ih current is necessary to maintain normal dopamine fluctuations and sleep consolidation in Drosophila.

HCN channels are becoming pharmacological targets mainly in cardiac diseases. But apart from their well-known role in heart pacemaking, these channels are widely expressed in the nervous system where they contribute to the neuron firing pattern. Consequently, abolishing Ih current might have detrimental consequences in a big repertoire of behavioral traits. Several studies in mammals have identified the Ih current as an important determinant of the firing activity of dopaminergic neurons, and recent evidences link alterations in this current to various dopamine-related disorders. We used the model organism Drosophila melanogaster to investigate how lack of Ih current affects dopamine levels and the behavioral consequences in the sleep:activity pattern. Unlike mammals, in Drosophila there is only one gene encoding HCN channels. We generated a deficiency of the DmIh core gene region and measured, by HPLC, levels of dopamine. Our data demonstrate daily variations of dopamine in wild-type fly heads. Lack of Ih current dramatically alters dopamine pattern, but different mechanisms seem to operate during light and dark conditions. Behaviorally, DmIh mutant flies display alterations in the rest:activity pattern, and altered circadian rhythms. Our data strongly suggest that Ih current is necessary to prevent dopamine overproduction at dark, while light input allows cycling of dopamine in an Ih current dependent manner. Moreover, lack of Ih current results in behavioral defects that are consistent with altered dopamine levels.

Physical strength, fighting ability, and aggressiveness in adolescents.

OBJECTIVES: Recent research suggests that evolutionary selection pressures have shaped mental mechanisms to be able to assess one's own and other's physical strength, fighting ability, and aggressiveness. According to the recalibrational theory, anger may be linked to fighting ability and serve as a bargaining mechanism to improve welfare obtained in social conflict. We hypothesized that late adolescent men (but not mid-adolescent men or women) use this mechanism, as it would be particularly adaptive for them to avoid potential costs from direct conflict in male competition. METHODS: The present study investigated the relationship between fighting ability (estimated from handgrip strength [HGS], a measure of upper body strength, and self-reported fighting ability) and aggressiveness (physical and nonphysical) in 288 Spanish adolescents aged 14-18 years. RESULTS: Our results indicated a positive relationship between self-perceived fighting ability and HGS in both sexes during adolescence. There was no association between fighting ability and aggressiveness in late adolescent women (17-18 years). For men, there was a positive relationship between fighting ability and physical aggression, but the strength of this relationship decreased with age. Additionally, for men, there was a positive relationship between fighting ability and anger but only in late adolescence, and thus arguing that for adolescent men aggression strategies shift from physical to nonphysical as they age. CONCLUSIONS: With reference to the recalibrational theory of anger, our results suggest that the sex- and age-dependent associations between fighting ability and physical and nonphysical aggression indicate divergent adaptive skills between sexes, which are driven by intrasexual competition.

Testosterone, facial symmetry and cooperation in the prisoners' dilemma.

Recent research has analyzed how individual characteristics, like the exposure to different hormones and symmetry, affect decision-making and strategic behaviour. The present article investigates the effect of symmetry, of exposure to testosterone (T) in utero and during puberty and of current T on cooperation in a Prisoners' Dilemma Game (PDG). T is a hormone with well known effect on males' behaviour, and that promotes activities that seek to increase reproductive success. Fluctuating Asymmetry (FA) reflects the ability of the organism to maintain a stable development and it is usually employed as a variable reflecting genetic quality (low FA values are thought to signal higher genetic quality). Our results show that subjects with intermediate levels of second to fourth digit ratio (a proxy of exposure to T in utero) and with high FA cooperate more often in the PDG. We also observe that the latter effect is due to the fact that FA has an impact on subjects' expectations about the behaviour of their counterpart in the game. These results reinforce the described link between markers related to genetic quality and cooperative behaviour. This possible linkage of individual condition and pro-social behaviour in humans clearly merits further attention.

Squeeze involvement in the specification of Drosophila leucokinergic neurons: Different regulatory mechanisms endow the same neuropeptide selection.

One of the most widely studied phenomena in the establishment of neuronal identity is the determination of neurosecretory phenotype, in which cell-type-specific combinatorial codes direct distinct neurotransmitter or neuropeptide selection. However, neuronal types from divergent lineages may adopt the same neurosecretory phenotype, and it is unclear whether different classes of neurons use different or similar components to regulate shared features of neuronal identity. We have addressed this question by analyzing how differentiation of the Drosophila larval leucokinergic system, which is comprised of only four types of neurons, is regulated by factors known to affect expression of the FMRFamide neuropeptide. We show that all leucokinergic cells express the transcription factor Squeeze (Sqz). However, based on the effect on LK expression of loss- and gain-of-function mutations, we can describe three types of Lk regulation. In the brain LHLK cells, both Sqz and Apterous (Ap) are required for LK expression, but surprisingly, high levels of either Sqz or Ap alone are sufficient to restore LK expression in these neurons. In the suboesophageal SELK cells, Sqz, but not Ap, is required for LK expression. In the abdominal ABLK neurons, inhibition of retrograde axonal transport reduces LK expression, and although sqz is dispensable for LK expression in these cells, it can induce ectopic leucokinergic ABLK-like cells when over-expressed. Thus, Sqz appears to be a regulatory factor for neuropeptidergic identity common to all leucokinergic cells, whose function in different cell types is regulated by cell-specific factors.