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[Resumen] El efecto de la edad relativa se refiere a las diferencias cronológicas de sujetos pertenecientes a un mismo grupo de edad, que puede provocar que los nacidos en los primeros meses del año parezcan más talentosos. El objetivo de este estudio fue analizar la posible existencia del efecto de la edad relativa en la natación española. Para llevarlo a cabo se consideraron los 100 mejores resultados en piscina de 50 metros de las últimas seis temporadas (2015-2021), para todas las edades de las categorías con campeonatos nacionales, en ambos sexos y en los cuatro estilos. El análisis se realizó sobre 28.373 resultados obtenidos de la base de datos de la Real Federación Española de Natación, tomando como referencia las fechas de nacimiento de los nadadores. Para identificar si existe el efecto de la edad relativa en la natación en España se aplicó el odds ratio y la prueba estadística chi cuadrado. Así, para calcular las posibles diferencias entre los rendimientos medios entre los trimestres de nacimiento de los nadadores, se realizó́ un análisis de varianza. Los resultados mostraron una distribución desigual de las fechas de nacimiento por trimestres y unos rendimientos medios diferentes para casi todos los grupos de edad, en ambos géneros. En conclusión, se puede decir que la sobrerrepresentación de deportistas en los primeros trimestres del año, y la diferencia en cuanto al éxito deportivo alcanzado, son dos efectos de la edad relativa a considerar. [Abstract] The relative age effect refers to chronological differences in subjects belonging to the same age group, which may cause those born in the first months of the year to appear more talented. The aim of this research is to analyse the effect of relative age in Spanish swimming. The 100 best results in pool of 50 meters of the last six seasons (2015-2021) were analysed for all ages of the categories with national championships, in both genders and in the four styles. The sample included 28.373 results obtained from the database of the Royal Spanish Swimming Federation, taking as reference the dates of birth of the swimmers. To analyse the effect of relative age in Spanish swimming, the Chi-squared statistical est was used. The possible differences between the average yields between the birth quarters of the swimmers was calculated by an analysis of variance. The results showed an unequal distribution of birth dates by trimesters and different average yields for almost all age groups, in both genders. In conclusion, it can be said that the over-representation of athletes in the first quarters of the year, and the difference in terms of sports success achieved, are two effects of the relative age to consider.

In this study, we explore the extent to which service-learning (SL) can enhance the educational potential of sport education (SE), with a view to contributing to a positive transition for students from primary to secondary school. Seventeen teachers and 435 eleven- to sixteen-year-olds across five SE networks participated in this study, in which an SL experience was embedded in the SE season. All the networks included one intact group of secondary school students and between one and three intact groups of primary school students. The programme comprised between 18 and 21 physical education (PE) lessons for each secondary school group, and between 14 and 18 PE lessons for each primary school group. A total of 40 volunteer secondary school students (28 girls and 12 boys) performed the role of SL coordinators, coaching primary school students in several sessions. The data were obtained through focus groups with students and primary school teachers and interviews with secondary school teachers during and after the programme implementation. The results were analysed through the lens of situated learning. The integration of SE and SL has led both to legitimate peripheral participation and real participation in the community of practice, through the connection established by SE roles. SL reconfigures SE, allowing purposes that might be of significant educational relevance to be addressed, such as a positive transition from primary to secondary school. The secondary school students who acted as SL coordinators assumed their responsibilities to a greater degree than in previous SE seasons and gained a deeper understanding of the roles.

The objective of this study was improved motor competence and social relationships among students with coordination and / or social difficulties, through an integrative program of reinforcement, from motor skills. To do this, the study was divided into four phases. In the first, among those 60 children participating in the third year of Early Childhood Education, were selected those susceptible to suffer difficulties with movement and / or deficits in their social relationships, after applying a different filter test. In the second and third phase, motor competence was evaluated through the Children's Movement Assessment Battery (MABC-2) and a physical literacy program was implemented aimed at the development of basic motor skills was implemented. Finally, in the fourth phase, it was checked whether there had been any improvement in the motor competence and social relations of the participating students. After intervention, significant improvements were found between the pre and post averages in the dimension balance, aim and catch and overall score, plus a significant improvement in positive friend. These results invite us to continue working to promote the adequate development among students in the infant stage, both at the motor and social levels. El objetivo del presente estudio fue mejorar la competencia motriz y las relaciones sociales en alumnado con dificultades de coordinación y/o sociales a través de un programa integral de refuerzo motriz. Para ello, el estudio se dividió en cuatro fases. En la primera fase se seleccionaron, de entre los 60 niños participantes de tercer curso de Educación infantil, aquellos susceptibles de sufrir dificultades de movimiento y/o déficit en sus relaciones sociales, tras la aplicación de una serie de pruebas filtro. En la segunda y tercera fase se evaluó la competencia motriz, mediante la Batería de evaluación del movimiento para niños (MABC-2) y se implementó un programa de alfabetización física orientado al desarrollo de las habilidades motrices básicas para, finalmente, en la cuarta fase, comprobar si se había producido alguna mejora en la competencia motriz y en las relaciones sociales del alumnado participante. Tras la aplicación de la intervención se comprobaron mejoras significativas entre las medias pre y post en la dimensión equilibrio, puntería y atrape y puntuación global ,además de una mejora significativa en amigo positivo. Estos resultados invitan a seguir trabajando en esta línea para favorecer un adecuado desarrollo de los alumnos de la etapa de infantil, tanto a nivel motriz como a nivel social. Esta pesquisa tem como objetivo melhorar a competência motora e as relações sociais em estudantes com dificuldades de coordenação e/ou sociais, por meio de um programa abrangente de reforço das habilidades motoras. Para isso, o estudo está dividido em quatro fases. Na primeira, foram selecionados entre os 60 alunos participantes do terceiro curso de educação infantil, aqueles suscetíveis de apresentar dificuldades de movimento e/ou de relações sociais, após a aplicação de uma série de testes de filtragem. Na segunda e terceira fases, avaliou-se a competência motora por meio da Bateria de Avaliação de Movimentos para Crianças (Mabc-2) e se implementou um programa de alfabetização física orientada ao desenvolvimento das habilidades motoras básicas; para, finalmente, na quarta fase, comprovar se houve melhora na competência motora e nas relações sociais dos participantes. Após a aplicação da intervenção, melhorias significativas entre as médias pré e post na dimensão equilíbrio, pontaria e captura e pontuação global , bem como uma melhoria significativa em amigo positivo. O que nos sugere a continuar trabalhando nesta linha para promover o desenvolvimento adequado dos alunos na fase infantil, tanto no nível motor quanto no social.

The Game Performance Evaluation Tool (GPET) is an instrument that allows us to obtain information about the student's decision-making process during their participation in games. The usual instruments reflect the final result of student's decision. However, the GPET offers an analysis of the context in which the decision has been made, and allows teachers to establish a certain degree of quality in the decision taken. Thus, the GPET helps us to distinguish in the decision-making process, not only "what has been done" from "what should have been done" in a specific game situation (Gutiérrez, González, García-López, Mitchell, 2011), but also it gives us information about the player's adaptation to the tactical context in which he/she is involved during game play. According Godbout (1990), this adaptation to the tactical context describes the decisional process, rather than the result. Given that the GPET is an instrument initially designed for research, in this article we present how to take advantage of the GPET novelties, applying them in an instrument with a clear teaching orientation, such as the Game Performance Assessment Instrument (GPAI) (Mitchell, Oslin and Griffin, 2013).Resumen. El Game Performance Evaluation Tool (GPET, en español Herramienta de Evaluación del Rendimiento de Juego), es un instrumento que nos permite obtener información sobre el proceso de toma de decisiones del alumno durante su participación en los juegos deportivos. Los instrumentos habituales reflejan el resultado final de la decisión del alumno. Sin embargo, el GPET hace un análisis del contexto en el que se ha tomado la decisión, y permite que el docente pueda establecer cierta gradación en la calidad de la decisión tomada. Así, el GPET nos ayuda a distinguir en la toma de decisiones no sólo “qué se ha hecho” de “qué se debería haber hecho” en una situación concreta de juego (Gutiérrrez, González, García-López, Mitchell, 2011), sino también nos aporta información de la adaptación del jugador al contexto táctico en el que se encuentra. Dicha adaptación, de acuerdo con Godbout (1990), nos describe el proceso decisional, más que el resultado. En este artículo presentamos como aprovechar las novedades del GPET, que es un instrumento inicialmente diseñado para el ámbito de la investigación, aplicándolas en un instrumento con una orientación claramente docente, como es el Game Performance Assessment Instrument (GPAI, en español Instrumento de Evaluación del Rendimiento de Juego, de Mitchell, Oslin y Griffin, 2013).

Differences in tactical knowledge of children aged seven-13 years from three different sports contexts (school, recreation and specific) were analyzed. Participants completed the Soccer Tactical KnowledgeTest and results were analyzed according to the age, experience and sport context of the individuals. Age and experience correlated significantly with the tactical knowledge (r = ,31; r= ,41; r= ,53), although the magnitude of these correlations was low (r < ,70) according to the consideration of results classified as acceptable coefficients (Gregory, 2000). Specific context participants showed significantly higher knowledge than the school context individuals: declarative (Z = -8,29; p = ,00; r = ,42), procedural (Z = -5,39; p = ,00; r = ,27) and tactical knowledge (Z = -6,85, p = .00, r = .34). Recreational context participants scored significantly higher than the school context individuals: declarative (Z = -6,63; p = ,00; r = ,36), procedural (Z = -5,15; p = ,00; r = ,28) and tactical knowledge (Z = -6,63; p = ,00; r = ,36). No differences were observed between specific and recreational contexts. Findings show that age and experience were not the main cause of the differences observed. Probably, the specific possibilities of learning of each context affected to the participants’ knowledge. More studies are needed to examine the relationship between tactical knowledge and other variables such as teaching sports methodologies employed in different sport contexts.

Since its introduction by OECD in 1997, the relevance of the concept of competence has been increasing within European education systems. The Spanish Education System has conferred competences a curricular key role in the last two education acts (LOE, 2006 and LOMCE, 2013). The implementation of a competence-based curricular approach involves bureaucratic changes, but above all methodological changes, whose main agent are teachers. After a decade of implementation, only a few studies have focused on the evaluation of this educational reform from teachers’ point of view. The aim of this study is to provide a national survey on Physical Education (PE) teachers’ perception of the competence-based curricular approach. A questionnaire was designed and validated to determine PE teachers’ perception of the contribution of PE to each key competence; teachers’ difficulties; and the suitability of the established PE curriculum to be carried out within the competence-based approach. A sample of 470 inservice PE teachers was obtained by using a random stratified sampling technique. Teachers showed a high perception of the potential contribution of PE to the development of the key competences, especially to those related to social and attitudinal aspects. Though, teachers believe that PE contents established in LOE are not suitable. Male, young, and public school teachers generally perceive a higher contribution of PE to the key competences than their fellow female, older, and private school teachers. Perceived difficulties in tasks development varied depending on educational stage and teachers’ experience.

Introduction This study examined the impact of a multicomponent physical activity (PA) intervention (MOVI-KIDS) on improving cognition in schoolchildren. This paper also analyzed the mediator role of motor fitness between MOVI-KIDS and cognition. Methods Propensity score analysis of data from a cluster randomized controlled trial (MOVI-KIDS study). This analysis including 240 5-7 years old children from nine schools in the provinces of Cuenca and Ciudad Real, Spain. MOVI-KIDS program consisted of: (a) three weekly after-school sessions of recreational non-competitive PA lasting 60 minutes during one academic year, (b) educational materials for parents and teachers, and (c) school playground modifications. Changes in cognition (logical reasoning, verbal factor, numerical factor, spatial factor, and general intelligence) were measured. A propensity score cross-cluster matching procedure and mediation analysis (Hayes's PROCESS macro) were conducted. Results All cognitive variables pre-post mean changes were significantly higher (P ≤ 0.05) in children from intervention schools than those from control schools (effect size ranged from 0.33 to 1.48). The effect of the intervention on the spatial factor and general intelligence was partially mediated by motor fitness (indirect effect = 0.92, 95% CI: 0.36; 1.65; and indirect effect = 1.21, 95% CI: 0.06; 2.62, respectively). Conclusions This study shows that a one-school-year multicomponent intervention consisting of a recreational non-competitive PA program, educational materials for parents and teachers, and school playground modifications improved the cognition of first-grade children. Further, our results suggest that the effect of the intervention on cognition was mediated by changes in motor fitness.

Cuando está cumplida una década desde que se propusiera el primer currículum LOGSE y con su reciente modificación para la etapa de Educación Secundaria, se presenta como necesaria una revisión del tratamiento de algunos de sus contenidos. Este es el caso de la fuerza como capacidad condicional. En este artículo nos preguntamos acerca del por qué de la mala prensa de la fuerza en la escuela, para después, partiendo de la referencia que suponen las fases sensibles y los factores que influyen en su desarrollo, realizar un análisis crítico de las propuestas curriculares para cada una de las etapas educativas. Como principal conclusión, podemos avanzar que el tratamiento curricular de la fuerza ha sido pobre, lo cual puede tener repercusiones negativas en los hábitos de salud de nuestros alumnos.

En este artículo nos hemos propuesto dar una serie de orientaciones sobre la iniciación al Baloncesto. Partiendo del estudio en profundidad de las características del niño/a, de los modelos alternativos en la enseñanza de los deportes basadas en el Constructivimo y de la experiencia obtenida durante veinte años de entrenamiento y de esfuerzo por mejorar el proceso de enseñanza-aprendizaje en el Club Polideportivo La Roda (sección de Baloncesto), dotando de mayor calidad a las programaciones por categoría. Todo ello, con la intención de formar a jugadores inteligentes con buenos conocimientos deportivos y a sabios espectadores.Abstract: In this article we have propose to give some orientations about Basketball initiation. Departing from study of the characteristics of the Childs, alternative models in the teaching of the sports based on the Constructivism and the experience obtained for twenty years of training and to effort for improving the process of education - learning in the Club Polideportivo La Roda (Basketball Department). This is in order to teach intelligent players and spectatorss.

espanolLos buenos resultados del trabajo de intervalos de alta intensidad (HIIT ) y ejercicios funcio nales en el ambito extraescolar han suscitado interes sobre el modo de introducirlos en Educacion Fisica (EF). El objetivo de este estudio fue conocer el potencial del Modelo de Educacion Deportiva (MED) con contenidos relacionados con la condicion fisica y analizar la adecuacion del sistema de trabajo HIIT y ejercicios funcionales en EF. Para ello , se analizo la percepcion de alumnado (n=205) y docentes (n=4) de Educacion Primaria (EP) y Educacion Secund aria (ES) a partir de una unidad didactica desarrollada con el MED (n=106) y otra con metodologia tradicional (n=99). Se midio la percepcion de los docentes mediante auto -informes y la percepcion del alumnado a traves de grupos de discusion (n=30). Los dat os se analizaron siguiendo las 5 fases propuestas por Yin (2011). Los resultados mostraron congruencia en la percepcion del MED con la literatura y la percepcion positiva , tanto de estudiantes como docentes , del sistema HIIT y ejercicios funcionales. En co nclusion, el MED podria tener un potencial educativo similar al presentado con los juegos deportivos , y el HIIT se muestra adecuado como alternativa al trabajo tradicional de la condicion fisica en EF EnglishThe positive results of high -intensity interval training (HIIT) and functional exercis es in the extracurricular field have raised interest in how to introduce them in Physical Education (PE). Th is study aimed to examine the potential of fitness content in Sport Education Model (SEM) and to analyze the adequacy of HIIT and functional exercises in PE. Primary and Secondary Education students (n=205) and teachers’ (n=4) perceptions were analyzed. Students were divide d into two groups to compare SEM (n= 106) and the traditional approach (n= 99). Teachers’ perception s were measured by self -reports and students’ perceptions by focus groups (n= 30). Yin’s (2011) phases were used to analyze the data. SEM r esults are consistent with literature and there is a positive perception of both, students and teacher, about HIIT and functional exercises. In conclusion, SEM could have an educational potential similar to that presented with games , and the HIIT could be an alternative to traditional fitness approach in PE

Background: One of the objectives of the new Spanish Education Act is for students to develop a series of social skills, largely derived from the ability variables of assertiveness and empathy. Sport Education is an instructional model that is deemed useful in the development of personal and social responsibility and social values. It requires interaction among students during group activities as there are many roles and responsibilities involved. Previous research on Sport Education reveals links between certain results and empathy and assertiveness, although no specific studies have been conducted. Purpose: The aim of this research study is to analyse the effect of a Sport Education season on student empathy and assertiveness. Participants and setting: Sport Education was implemented in seven intact groups at five different schools in central Spain. 154 subjects (76 boys and 78 girls) participated in this study, 34 of whom were in primary education year five (11 years), 98 in primary education year six (12 years) and 22 in secondary education year two (14 years). Research design: A single treatment pre-post test design was applied, in which the tests for measuring the dependent variables (empathy, assertiveness) influenced by the independent variable (the Sport Education season) were applied before, during and at the end of the programme. Data collection: The Empathy Questionnaire (Mehrabian and Epstein, 1972), and the Children?s Assertiveness Behaviour Scale (Michelson and Wood, 1982) were used to measure dependent variables. Data analysis: Analysis of variance was conducted to ascertain the influence of Sport Education on groups and teams. Student t tests were conducted to establish individual differences between pre-test and post-test, and analysis of variance was conducted to measure the influence of factors such as gender and role on each variable. Repeated measures analysis of variance was conducted to establish differences between the various points at which the programme was applied. Findings: Positive results were obtained in assertiveness, where differences were significant between pre-test and post-test, although effect size differed from case to case. Group and team were a key aspect when differences were significant. Conclusions and implications: Sport Education was shown to be a useful instructional model for improving a variable(assertiveness) directly related to personal and social responsibility. Nevertheless, teachers need to design and apply pedagogical strategies routinely, and pay very close attention to the dynamics created in the classroom, in order to achieve these results. Further research involving more specific testing of classroom situations in general and Physical Education situations in particular is also required. Keywords: physical education, sport education, empathy, assertiveness, social relations.

Summary.—This cross-sectional study investigated the differences between young expert soccer players’ (n = 55) and novice players’ (n = 74) decision-making ability during performance of invasion games (ages: 7–8, 9–10, 11–12, and 13–14 years). Decision-making ability was assessed in invasion games that were appropriately modified for age and expertise. Games were modified to meet the developmental needs and previous learning of the participants, so interference between motor execution and decision making was minimized. Game performance was videotaped, and measures of cognitive components were developed from observational analysis. Decision making was measured at two levels: (a) decision making restricted to the selection of the technical-tactical skills (passing, moving with the ball, getting free, marking, tackling, double teaming, and interception) and (b) decision making in the adaptation to the tactical context of the game. Expert players remained superior in decision-making ability when variation in skill execution was controlled. Decision-making differences between levels of expertise decreased with age with regard to the first level (skill selection) and increased with age in relation to the second level (tactical-context adaptation). Findings are discussed in terms of implications for instructional focus and task design. This study examined the differences in the cognitive components of game performance among invasion game players with different levels of expertise. The study contributes to the expert–novice and decision-mak ing literature in two ways: first by investigating the interaction of skill execution and decision making, and second by the assessment of the decision-making component of performance in skill selection and tactical adaptation to the game context. Within expert–novice studies, expertise has typically been a dependent variable to compare players with different levels of sport perfor mance. The main aims of these studies have been the understanding of the features that distinguish experts from novices, and the processes underlying the development of expertise. Expertise is defined as the result of the successful interaction between biological, psychological, and social 1

Resumen basado en el de la publicación Se pretende evaluar el conocimiento técnico-táctico (declarativo y procedimental) en jóvenes jugadores de fútbol con alto nivel de pericia. A catorce jugadores de 12 años del Albacete Balompié, se les realiza un test de juego grabado en video basado en un juego modificado de fútbol: 5 contra 5, para lo que se usó la Herramienta de Evaluación del Rendimiento de Juego (HERJ). Su objeto es evaluar el rendimiento de los componentes individuales y grupales del juego (toma de decisiones y ejecución). A continuación se les realizan dos entrevistas para evaluar su conocimiento de base. En la primera entrevista se les pregunta por el conocimiento relativo a los deportes de invasión tomando como referencia el fútbol. En la segunda entrevista se analiza su conocimiento procedimental a partir de secuencias de video de juego en fútbol A-7. Los resultados revelan que los jugadores de fútbol de 12 años tienen un alto rendimiento de juego en las acciones seleccionadas, especialmente en la toma de decisiones, pero este nivel no se muestra tan elevado en el conocimiento teórico medido en las entrevistas. Madrid Biblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 planta; 28014 Madrid; Tel. +34917748000; biblioteca@mecd.es ESP

The purpose of this study is to assess the technical-tactical knowledge of high performance soccer players. The sport performance of sixteen 14-year-olds who play for the Spanish soccer club Albacete Balompie was analysed in a modified game as “seven-a-side match” using video assessment (Game Performance Evaluation Tool, GPET), this tool evaluates decision making and execution: control, dribbling, passing, shooting, getting free, set, marking, clearance, tackling, locking, trapping/interception, and defence help/double teaming. The players were interviewed twice to ascertain their basic knowledge. In the first interview they were asked about their knowledge of invasion games, taking soccer as a reference. In the second interview their procedural knowledge was analysed using video sequences of real game play from a “seven-a-side match”. The results revealed that players acquired game performance (decision-making and execution) before specific game knowledge. They also performed better in response selection than response execution, and showed a greater command of offensive play and individual aspects of the game, both in terms of knowledge and game situations.

Expert and novice soccer players (N=140) from five different competition levels (inexperienced, provincial, regional, national and international levels) were examined for differences in procedural knowledge. A video-based test was developed recording four matches of the under-16 Spanish football final play-off. Ten sequences, seven offensive and three defensive, were finally selected for the video test. Analysis of variance indicated that no significant differences were found in procedural knowledge among the different competition levels but when combined, subjects belonging to the national and international level had a significantly higher rate of procedural knowledge than regional, provincial and inexperienced soccer players. Experts were less homogeneous as a group when compared to novices. No differences were found between defenders and midfielders in any category, although midfielders have to perform in more varied and tactically complex contexts than defenders.

The prevention of obesity and improvement of academic achievement in children are concerns of industrialized societies. Obesity has been associated with psychological disorders, including attention deficit hyperactivity disorder, whose prevalence has been estimated at 6.8 % in Spanish children and adolescents. It is known that physical activity is positively related to academic achievement and negatively related to the risk of obesity in children. However, studies to test the effectiveness of physical activity interventions in improving academic achievement in preschool children are scarce and have some weaknesses that threaten their validity. Moreover, very few studies have examined their effectiveness in improving symptoms of attention deficit hyperactivity disorder. This paper outlines a two-year multidimensional preschool intervention (Movi-Kids) aimed at preventing obesity and improving academic achievement in children with or without attention deficit hyperactivity disorder. Twenty-one schools from Ciudad Real and Cuenca, Spain, were randomized to intervention and control groups. In the first academic year, children in the third grade of preschool and the first grade of primary school in the intervention group received the Movi-Kids intervention. In the second academic year, schools were crossed over to the other group. The intervention included children, parents and teachers, and the school environment, and consisted of: (i) three hour-long sessions of recreational non-competitive physical activity after school, weekly, (ii) educational materials for parents and teachers addressing sedentary lifestyle risks and (iii) playground modifications to promote physical activity during breaks. Primary outcome measures of this study were academic achievement (intelligence, cognition, memory, attention and perception), assessed by the Battery of General and Differential Aptitudes, and adiposity measures (body mass index, waist circumference, triceps skinfold thickness and body fat percentage). Secondary outcome measures were: attention deficit hyperactivity disorder risk, motor skills, health-related quality of life and sleep quality. These variables will all be measured in both groups at baseline and at the end of the first and second academic years. It seems reasonable that an intervention to promote physical activity based on playground games will be useful for simultaneously improving academic achievement and controlling obesity. ClinicalTrials.gov NCT01971827 .

La Educación Deportiva es un modelo de instrucción proveniente del mundo anglosajón al cual se le atribuye el desarrollo de la empatía, la asertividad y la mejora de las relaciones sociales. El objetivo de nuestro estudio ha sido contrastar dicha atribución. Para ello se ha implementado el modelo con un grupo de 21 sujetos (10 varones y 11 mujeres) de quinto de Educación Primaria durante 18 sesiones, evaluando mediante test-retest dichas variables. Los diferentes ANOVA realizados mostraron que el programa no ha mejorado la empatía, la asertividad, las conductas agresivas, los amigos positivos y los amigos negativos en el total del grupo. Sin embargo, sí se obtuvieron mejoras significativas en la disminución de las conductas pasivas en el total del grupo, la agresividad en función del rol desempeñado, el aumento del amigo positivo dentro del equipo al que se pertenece, y la disminución del amigo negativo en las niñas.