[Oxytocin and vasopressin: sexual differences and clinical implications]. / Oxitocina y vasopresina: diferencias sexuales y sus implicaciones clínicas.

Oxytocin and vasopressin share a similar chemical structure but have different functions. Both hormones are produced in different brain areas, are transported through the hypophyseal portal system, pass to the anterior hypophysis, and released to reach their target organs. These hormones also act as neuromodulators, where its receptors are found in the lateral septum, the middle amygdala, the hippocampus, the hypothalamus, and the brain stem. These brain structures regulate socio-sexual behaviors in vertebrates. Moreover, the oxytocinergic and the vasopressin systems are sexually different. The sexual steroids promote oxytocin release and the oxytocin receptor synthesis, as well as promoting or inhibiting vasopressin release and its receptor genetic transcription. Both neuropeptides are involved in social recognition, male-female pair bonding, aggression, and cognition. Furthermore, the disruption or malfunctioning of the oxytocin and vasopressin systems adds to the causes of some psychiatric disorders like depression, schizophrenia, autism, and borderline personality.

La oxitocina y la vasopresina son similares en estructura química, pero difieren en sus funciones. Ambas se producen en diversas áreas del cerebro, se transportan a través del sistema porta hipofisario a la hipófisis anterior y se distribuyen a sus órganos blanco actuando como hormonas. Estas fungen también como neurorreguladores, con receptores dispersos en el septum lateral, la amígdala central, el hipocampo, el hipotálamo y el tronco encefálico, estructuras asociadas a la conducta sociosexual en todos los vertebrados. Los sistemas vasopresinérgico y oxitocinérgico difieren entre los cerebros femenino y masculino. Aunado a esto, los esteroides sexuales intervienen en la expresión de los genes para oxitocina, la síntesis de sus receptores y su liberación. Además, promueven o inhiben la transcripción de los genes para vasopresina. Ambos neuropéptidos participan en el reconocimiento social, el vínculo de pareja, la cognición y la agresión. La disrupción de los sistemas de estos neuromoduladores se suma a las causas de algunos desórdenes psiquiátricos, como la depresión, la esquizofrenia, el autismo y la personalidad limítrofe. Esta revisión está enfocada a describir las diferencias entre géneros, tanto de la síntesis, como la distribución de los receptores y los efectos que generan la oxitocina y la vasopresina en la conducta para comprender la prevalencia, la sintomatología y la respuesta a los tratamientos a dichas patologías.

The effects of female-male friendships on male postcopulatory levels of oxytocin and vasopressin, and sperm parameters in Macacaarctoides.

Male and female stump-tailed macaques (Macaca arctoides) form close relationships akin to human friendships. Oxytocin and vasopressin modulate these and other social relationships and reproductive behavior and physiology in various mammal species. Besides the behavioral effects of oxytocin, this hormone plays an essential role in the ejaculatory process, favoring sperm transport upward the female reproductive tract. Therefore, we investigated the influence of friendships on postcopulatory serum levels of oxytocin and vasopressin in the stump-tailed macaque (Macaca arctoides). In addition, we searched for a correlation between this kind of social relationship and sperm transport in the vagina during the periovulatory and luteal phases. Six female and six male adult macaques having different friendship indices served as experimental animals. Allocated in 57 mating pairs combinations, these animals were allowed to copulate once in the luteal and periovulatory phases. Blood samples were collected from each animal finishing copulation to measure oxytocin and vasopressin. Afterward, we profoundly sedated the females and collected three semen samples from the vagina every 10 min to perform spermatobioscopies. Males' post-copulation oxytocin values increased along with the friendship index, while vasopressin behaves oppositely. Sperm concentration and immotile and motile sperm decreased from one sample to another as male-female closeness increased. Finally, in the periovulatory phase, only in the first vaginal sample, sperm velocities significantly increased with friendship indices. Our results showed that in stump-tailed macaques, heterosexual friendships promote higher postcopulatory oxytocin concentrations and better physiological conditions to males, which probably enhance reproductive success.

Potential Food Availability Influences Social Interactions of Young Individuals in a Neotropical Primate (Alouatta palliata).

Deforestation is widely recognised as an agent of human disturbance that causes widespread destruction of species habitats and can result in animals occupying forest patches with limited food resources. When animals are forced to change habitats, they must also adjust their diet, activity budgets and social behaviour in response to facing new ecological and environmental conditions. Only a few studies have analysed the influence of habitat conditions on social interactions of immature howler monkeys. In this study, we examined the effects of variation in food availability on social interactions of young howler monkeys (Alouatta palliata mexicana). This was accomplished by observing infant and juvenile members of two groups inhabiting a continuous forest habitat (640 ha) and three groups living in different-sized forest fragments (4, 42 and 93 ha) for a 15-month non-consecutive period. We quantified the Potential Food Availability Index (PFAI) for each habitat type based on the basal area, the Shannon-Wiener diversity index and abundance of food tree species. We used 15-min focal animal sampling to record the occurrence and/or duration of affiliative and agonistic behaviours. In habitats with higher PFAI, we observed more social play and proximity in infants aged 4-7 months, grooming in infants aged 8-14 months and social play in juveniles. Conversely, juveniles' grooming rates and 0- to 3-month-old infants' proximity rates decreased as PFAI increased. Our results suggest that food resource variation influences young howler monkeys' social interactions. The reduction in social interactions due to low food availability may represent an energy-saving strategy to cope with limited resources in habitats disturbed by anthropogenic activities.

Testosterone, the progesterone/estradiol ratio, and female ratings of masculine facial fluctuating asymmetry for a long-term relationship.

Idiosyncratic variation within the normal range of androgens levels in women account for significant variations in personality and behavior. We studied if testosterone introduces significant biases in women's perception of fluctuating symmetry of male faces suitability for a long-term relationship. Participants were 145 female college students asked to rate in a two-choice forced paradigm the attractiveness, suitability as a long-term partner, and economic success, fatherliness and fidelity of an asymmetric and a symmetric male face. Since our sample consists of random women interested in participating, whether for personal reasons or because they were paid to participate, we controlled for menstrual phase. All participants provided salivary samples to determine testosterone (T), estradiol (E2) and progesterone (P4) levels. When the P4/E2 was low and T low-to-normal, the symmetric face was rated as more attractive, and a desirable long-term partner, but these preferences changed to the opposite when P4/E2 was high. In high T women, neither face was rated as more attractive, independently from the P4/E2 ratio, but the asymmetric face was preferred as a long-term partner when conception risk was high, changing to prefer the symmetric face as the P4/E2 increased. The overall perception of male faces was that the symmetric face was more economical successful but a poor parent and highly unfaithful compared to the asymmetric face. A significant interaction between T and P4/E2 for ratings success of the asymmetric face suggests that high levels of feminine T might be related to inter-sexual competition when conception risk is high.

Waist-to-Hip Ratio, but Not Body Mass Index, Is Associated with Testosterone and Estradiol Concentrations in Young Women.

We studied if testosterone and estradiol concentrations are associated with specific female waist-to-hip ratios (WHRs) and body mass indices (BMIs). Participants were 187 young women from which waist, hips, weight, and height were measured. In addition, participants informed on which day of their menstrual cycle they were and provided a 6 mL saliva sample. Ninety-one of them were in the follicular phase and 96 in the luteal phase. Only in the fertile phase of the menstrual cycle we found a significant interaction between testosterone and estradiol affecting WHR (b ± s.e. = -0.000003 ± 0.000001; t 94 = -2.12, adjusted R (2) = -0.008, P = 0.03). Women with the highest levels of both hormones had the lowest WHRs, while women with low estradiol and high testosterone showed the highest WHRs. BMI significantly increased as testosterone increased in female in their nonfertile days.

Effect of photoperiod on characteristics of semen obtained by electroejaculation in stump-tailed macaques (Macaca arctoides).

Some environmental variables determining seasonal reproduction in mammals are temperature, humidity, food availability, and photoperiod. Among these, photoperiod is considered the main regulator of primates' seasonal reproduction, thus the latitudinal distribution of primate populations is a key factor determining the appearance of seasonal reproduction. The present work presents supporting discrete seasonality in male stump-tailed macaques (Macaca arctoides). We investigated whether semen quality and testosterone covaried with Mexico City's photoperiod and relative humidity by analyzing variations in the portions that form the ejaculate: the seminal liquid, the seminal coagulum, and the copulatory plug. Five male adult stump-tailed macaques were electroejaculated once a month, obtaining three semen samples per male, from August 2011 to July 2012 (except for December 2011) (n = 165). Our results showed that stump-tailed macaque sperm counts were significantly different between the portions of the ejaculate. The seminal coagulum contained the significantly largest number of spermatozoids, followed by the copulatory plug and the seminal fluid. Photoperiod and relative humidity had major influence on the sperm count in the seminal coagulum and the testosterone concentrations. Testosterone reached its highest values around the time when days and nights lasted the same hours, decreasing when days either grew longer or became shorter. Concerning relative humidity, sperm counts in the seminal coagulum were highly variable on dry days, but decreased as the relative humidity increased. We conclude that stump-tailed macaques have a discrete seasonality, occurring in spring and fall when macaques' reproductive condition and readiness for postcopulatory intrasexual competition increase.

Changes in Men's Salivary Testosterone and Cortisol Levels, and in Sexual Desire after Smelling Female Axillary and Vulvar Scents.

Several studies have shown that a woman's vaginal or axillary odors convey information on her attractivity. Yet, whether such scents induce psychoneuroendocrinological changes in perceivers is still controversial. We studied if smelling axillary and vulvar odors collected in the periovulatory and late luteal phases of young women modify salivary testosterone and cortisol levels, as well as sexual desire in men. Forty-five women and 115 men, all of them college students and unacquainted with each other, participated in the study. Female odors were collected on pads affixed to the axilla and on panty protectors both worn the entire night before experiments. Men provided five saliva samples, a basal one before the smelling procedure, and four more 15, 30, 60, and 75 min after exposure to odors. Immediately after smelling the odor source, men answered a questionnaire rating hedonic qualities of scents, and after providing the last saliva sample they answered questionnaire on sexual desire. We found that periovulatory axillary and vulvar odors increased testosterone and cortisol levels, with vulvar scents producing a more prolonged effect. Luteal axilla odors decreased testosterone and cortisol levels, while luteal vulva odors increased cortisol. Periovulatory axilla and vulva scents accounted for a general increase of interest in sex. These odors were also rated as more pleasant and familiar, while luteal vulvar odors were perceived as intense and unpleasant.

Aging-related reproductive decline in the male spider monkey (Ateles geoffroyi).

BACKGROUND: It is unknown whether male black-handed spider monkeys (Ateles geoffroyi) undergo a reproductive decline as they age. The purpose of this work was investigating whether serum testosterone and semen quality decrease with age in these primates as occur in other species. METHODS: In this study, we assessed age variations in the concentration of serum testosterone, sperm counts, and motility in nine males. We took serum blood samples and semen samples by electroejaculation of anesthetized males throughout the fertile season. RESULTS: We found that testosterone levels and total sperm concentration, motile, progressive, fast linearly moving, medium linearly moving, slow linearly moving and immotile sperm significantly decreased with age. CONCLUSIONS: Our results show that a reproductive decline occurs in male spider monkeys because of a decrease in sperm counts. These results are similar to those of rhesus monkeys and men, despite the phylogenetic distance between New and Old World primates.

Seasonality of LH, testosterone and sperm parameters in spider monkey males (Ateles geoffroyi).

There are no reported data on hormonal fluctuations in black-handed spider monkey males. On previous research about the reproductive physiology of this monkey we have found that during the dry season females show ovulatory estrogen peaks and males present the best quality semen. As part of an ongoing research, in this study we assessed seasonal variations in the concentration of serum luteinizing hormone (LH) and testosterone (T) in three adult spider monkey males to corroborate the seasonal reproductive synchrony. At the same time sperm count and motility were evaluated to search for any correlation between those sperm parameters and hormonal concentrations. We took blood and semen samples (by electroejaculation) of anesthetized males throughout the rainy (June-September) and dry (October-May) months. Our results revealed that T and LH were higher throughout the dry season and there was a significant correlation between T concentration and sperm count. Although higher during the dry season, sperm motility tended to correlate with testosterone and LH levels. These results demonstrated that black-handed spider monkeys have a tendency to show a seasonal pattern of reproduction being the dry season the most likely time to achieve fertilization.

The seminal coagulum favours passage of fast-moving sperm into the uterus in the black-handed spider monkey.

In addition to gametes, mammalian internal fertilisation has required the evolution of assorted anatomical, physiological and biochemical devices to deal with intra- and inter-sexual conflict such as sperm competition and female cryptic choice respectively. The seminal coagulum of primates and other mammals is viewed as one of such devices. Among primates, the seminal coagulum characteristically occurs in multi-male and multi-female species, leading us to suppose that it intervenes in sperm competition. However, it can also provide cues to the female reproductive tract about male desired or undesired traits, and therefore deter or favour sperm survival and migration. The present work investigates whether the seminal coagulum of the black-handed spider monkey enhances sperm fertilisation chances by improving the female reproductive tract conditions, and if the female reproductive tract is 'blind' to semen or behaves selectively towards ejaculates of different males. A series of artificial inseminations were done in five females, using the ejaculates of three different males, one at a time, and measuring the presence of distinct types of sperm inside the uteri at 10, 30 and 60 min following the insemination. The presence of coagulum, menstrual phase, and male and female identity only affected fast, straight-moving sperm, with larger amounts of fast sperm appearing inside the uteri when ejaculates had seminal coagulum, as well as when in the periovulatory phase. There was great intra-uterine fast-sperm variation regarding which male's semen inseminated which female. The results provide evidence to account for sexual conflict in the spider monkey as well as a methodological approach to this kind of study.

Endocrine changes in male stumptailed macaques (Macaca arctoides) as a response to odor stimulation with vaginal secretions.

In mammalian species, social chemosignals are important in modulating endocrine reproductive functions. In nonhuman primates, previous studies have described a high frequency of mounting behavior by females in the follicular and periovulatory phases of the menstrual cycle. Stumptailed macaque females do not signal receptivity by means of sexual swellings, as do others macaques, therefore providing a good model in which to study chemical signaling of reproductive status. We exposed anesthetized stumptailed males to vaginal secretions of either late follicular or menses phase or to saline solution to determine the endocrine changes promoting male sexual behavior. In males exposed to follicular secretions, plasma testosterone concentrations were sustained up to 120 min after exposure. Such an effect was not observed in animals exposed to menses or saline odor sources. A luteinizing hormone surge, occurring 30 minutes after exposure to late follicular phase secretion swabs, preceded this sustained testosterone effect. The fact that late follicular scents induce sustained testosterone concentrations provides support to the idea that stumptailed males draw information concerning female reproductive status from the female's vaginal odor.

Sperm quality differences between the rainy and dry seasons in captive black-handed spider monkeys (Ateles geoffroyi).

The present work provides an assessment of sperm measures (concentration, motility, viability, etc.) of three black-handed spider monkeys (Ateles geoffroyi) during the rainy and dry seasons in Mexico City, as well as an evaluation of the between-subjects variability of sperm quality. Twenty samples obtained by rectal electroejaculation and digested with trypsin were evaluated. The results showed that during the dry season (n = 9) the semen samples were of better quality than those obtained during the rainy season (n = 11). The individual animals showed differences in sperm concentration, although there were no differences in sperm quality.

Comunicación química en primates / Chemical communication in primates

El sistema olfatorio de los mamíferos se ha especializado en la percepción de componentes químicos que regulan una gran diversidad de funciones. Uno de los componentes químicos que más utilizan las distintas especies es la feromona, cuyos efectos se pueden encontrar en el ámbito fisiológico o conductual, dependiendo del mensaje que se emita y del contexto en el cual se perciba.El uso de las feromonas en la comunicación química de los mamíferos tiene importantes funciones reguladoras de procesos reproducticos, que pueden afectar las interacciones sociales dentro de las poblaciones. Las feromonas que más emplean los mamíferos se encuentran en la orina y en las secreciones vaginales. La percepción de estos componentes químicos se lleva a cabo por el epitelio olfatorio y el órgano vomeronasal, que establecen conexiones neurales con diferentes núcleos cerebrales vinculados con la regulación del proceso reproductivo y las emociones. Sin embargo, hay controversia sobre la presencia de las feromonas en los antropoides del Viejo Mundo y en los seres humanos. En los primates, como los prosimios y los monos del Nuevo Mundo, se acepta su función en las conductas de marcaje territorial, en el reconocimiento entre conespecíficos y en la conducta sociosexual. En los primates catarrinos, en los póngidos y en los seres humanos se ha generado controversia sobre la participación de las feromonas en la atracción sexual. En primer lugar, debido a que esos grupos de primates muestran una disminucion de la región olfatoria, tanto nasal como cerebral, en comparación con el resto de los mamíferos. En segundo lugar, porque hasta ahora no se ha demostrado la funcionalidad del órgano vomeronasal, supuestamente especializado en la percepción de las feromonas en los demás mamíferos, que se considera como vestigial en los monos catarrinos y en los simios. Hay algunos trabajos sobre los seres humanos que muestran que dicho órgano no es completamente vestigial, como se consideraba, sino que es una estructura especializada en la percepción de feromonas, capaz de promover cambios fisiológicos dependientes del sexo.

Actualización por temas. Moon cycle effects on humans: myth or reality?

Durante siglos se ha mantenido la creencia popular de que el ciclo lunar influye en los factores fisiológicos y conductuales de los seres humanos. Esta idea podría explicarse por la cronobiología, pues esta perspectiva sugiere que los patrones conductuales de los organismos son el resultado de la interacción entre el programa temporal endógeno, que genera los ritmos biológicos, y las modificaciones causadas por los estímulos externos, como los ambientales y los sociales. Sin embargo tales interacciones pueden ser enmascaradas por efectos no naturales, como la luz eléctrica y los ruidos de la ciudad, entre otros. Diversas investigaciones han buscado la relación causal entre el ciclo lunar y los factores fisiológicos: las admisiones a los hospitales psiquiátricos, los traumas mentales, la conducta anormal, la actividad criminal, los intentos de homicidio y el suicidio, etc. No obstante los estudios han tenido un carácter epidemiológico, con extensas muestras poblacionales, y han obtenido resultados contradictorios debido, principalmente, a la manipulación estadística de los datos. Las relaciones entre el ciclo lunar y el periodo de sueño-vigilia de los seres humanos ha sido poco estudiado y no ofrece resultados convincentes. Por otro lado, los estudios sistematicos en los que se han usado métodos robustos, en los animales han proporcionado fuertes evidencias acerca de la alteración de los ritmos de reposo-actividad, en relación con las fases del ciclo lunar. Proponemos que se hagan estudios comparados en los seres humanos, con métodos confiables de registro y de observación sistemática que aporten datos más objetivos, capaces de distinguir los factores que probablemente estén enmascarando los efectos del ciclo lunar en la vida humana.

Un modelo de estrategia social durante el reposo nocturno en los macacos cola de muñón (Macaca artoides), en cautiverio exterior / A model of social strategy during nocturnal rest in Macaca arctoides in outdoor captivity

Las estrategias sociales son conductas complejas que los individuos elaboraron con el objeto de obtener beneficios dentro del grupo al que pertenecen. Es así que en los grupos de primates no-humanos, dichas estrategias se reflejan en la forma como el individuo se comporta para obtener alimento, su capacidad para establecer "buenas" relaciones con sus compañeros de grupo, el pertenecer a un status social alto y acceder a la cópula, entre otras. Este conjunto de conductas se han estudiado en el periodo de vigilia. Sin embargo, durante la noche parecen sucederse conductas que sugieren un modelo de estrategia social, que se relaciona con calidad del sueño. En la presente investigación se estudiaron las conductas diurnas y nocturnas, así como las pautas conductuales de sueño en relación al parentesco y al género, en todas las categorías de edad de un grupo heterosexual de 10 macacos cola de muñón (M. arctoides). Este grupo se encuentra en cuativerio exteior en el Departamento de Etología de la División de Neurociencias del Instituto Mexicano de Psiquiatría. Mediante la técnica no-invasiva de filmación con una cámara de alta sensibilidad, se hicieron registros nocturnos con una duración total de 60 horas. Los datos se sometieron a un análisis de tablas de contingencia multidimensionales, con el género y el parentesco como factores, de acuerdo con un modelo log-lineal. Después, se calcularon los residuos estandarizados para evaluar las diferencias entre las frecuencias observadas y predichas de cada conducta, con la prueba de chi cuadrada. Se observó una diferencia en la conducta de juego y en la de sacudirse en relación con el parentesco. También se encontraron diferencias significativas en las conductas de sacudirse, de aseo social, de agresión, consolidación y sueño, con respecto al género

Behavioral characterization of sleep in stumptail macaques (Macaca arctoides) in exterior captivity by means of high-sensitivity videorecording.

There are reasons to consider incomplete the description of sleep in many non-human primate species. Recording animals by highly sensitive videos to obtain detailed descriptions of nighttime behavior and evidence of muscle activity while in a resting posture, seems a promising approach to the non-invasive study of sleep in non-human primates. The present work describes the use of ultrasensitive videocameras to record and analyze spontaneous nighttime behaviors in captive non-human primates. Its main purpose is to emphasize the utility of videorecordings to analyze nighttime behavior. A heterosexual group of nine stumptail macaques (M. arctoides) was studied. It was possible to identify resting postures: immobility or lying on the floor as well as sleep movements and behavioral signs of sleep. This procedure permits recognition of each animal individually and the data suggest that videorecordings, among other techniques available, may be a useful, non-invasive method to study sleep. © 1995 Wiley-Liss, Inc.

Conductas de reposo (letargo) de los macacos cola de muñón (Macaca arctoides) en cautiverio, causadas por un eclipse solar / Resting (lethargic) behaviors of captive stumptail macaca (Macaca arctoides) caused by a colar eclipse

Se estudió la influencia de un eclipse total del sol (México, 11 de julio de 1991) sobre el comportamiento de un grupo de macacos cola de muñón (M. arctoides) que viven en cautiverio exterior. Se empleó un grupo heterosexual de nueve monos de diferentes edades y cada sujeto sirvió como su propio control. Los animales fueron filmados durante aproximadamente una hora continua el día del eclipse (de 1300 a 1405 h), para comparar sus reacciones conductuales con aquellas observadas durante el anochecer y amanecer en días veraniegos ordinarios (de 19:00 h de un día a las 06:00 h del día siguiente). Durante la fase de totalidad del eclipse (13:20 h), los animales formaron un solo grupo y ascendieron lentamente a la plataforma superior dentro del área de vivienda. Este lugar fue el sitio principal para dormir durante los días de control. Mostraron conductas de búsqueda grupal de abrigo, disminuyó la actividad motora y guardaron absoluto silencio. Conforme finalizó el eclipse, la actividad general volvió a la normalidad. Las reacciones conductuales fueron iniciadas por una hembra juvenil, incluyendo una conducta atípica de exploración. Los resultados sugieren que el cambio en el nivel de iluminación fue el factor principal que afectó la conducta de los primates, lo que confirma la dependencia fotoperiódica de sus sistemas circadianos de reposo

Conductas de exploración y variables sexo-edad en macacos cola de muñón (Macaca arctoides): una aproximación experimental / Exploration behaviors and sexual and age variables in stump-tail monkys

Los macacos cola de muñón (Macaca arctoides) tienen una organización social compleja. Cada individuo del grupo tiene un rol particular que difiere de sus compañeros de acuerdo al sexo y la edad, así como las relaciones de parentesco y el rango. En el contexto social este rol habilita a cada individuo del grupo para paticipar en un juego estratégico cognoscitivo. En consecuencia, los individuos pueden desplegar respuestas o estrategias conductuales diferenciales, durante los procesos de aprendizaje, particularmente si están en un contexto social. En el presente trabajo observamos las conductas exploratorias exhibidas como indicadoras de un proceso de aprendizaje en tres tropas de macacos cola de muñón (8, 8, y 10 respectivamente). Estos animales están mantenidos en cautiverio exterior en el Departamento de Etología y Bioterio, División de Investigaciones en Neurociencias del Instituto Mexicano de Psiquiatría. cada grupo está compuesto de individuos de ambos sexos y de todas las categorías de edad. Se utilizó una jaulilla experimental (objeto novedoso), la cual fue expuesta en cada una de las tropas, en sesiones de una hora diaria, durante tres días. Las sesiones fueron grabadas en cinta magnética y analizadas posteriormente. Las pautas conductuales consideradas fueron: aproximación, contacto, ingreso, tiempo medio de permanencia y latencia de contacto. En los análisis de los resultados encontramos que los adultos inician la actividad exploratoria; los infantes tienden a permanecer mayor tiempo en interación con el estímulo; las hembras parecen presentar menos temor al ingresar dentro del objeto novedoso. Discutimos los resultados con base en las habilidades requeridas en los procesos de aprendizaje, como la memoria y la atención; también la relación con la ontogenia de la conducta exploratoria, que en infantes, juega un papel de importancia en la adquisición de sus futuros roles sociales