Knowledge representation and problem solution in expert and novice youth baseball players.

The purpose of this study was to examine differences in knowledge representation and problem solutions in expert and novice youth baseball players. Ninety-four players in two age divisions, 7-8 years of age and 9-10 years of age, were assigned to three levels of expertise: high; average; and low skilled. Each subject participated in an interview session to elicit knowledge representation and solutions to five different defensive game situations. Interviews were transcribed and analyzed for content, solution to the problem, errors in problem solution, and qualitative trends. The frequency of advanced solutions to each of the five situations were analyzed in separate chi-square tests for age and expertise. Differences among the levels of expertise were found for the accuracy of solutions to three complex situations. Age was significant for only one situation. Patterns of knowledge content accessed during advanced and less advanced responses indicated both experts and novices were in a beginning stage of developing baseball knowledge structures. Errors in problem solutions indicated children had difficulty monitoring critical conditions and making correct inferences. Players' and teammates' ability to execute baseball skills seemed to influence the content and structure of tactical knowledge accessed during problem solution.

Expert-novice differences in cognitive and skill execution components of youth baseball performance.

Previous research has shown that experts exhibit superior response selection and skill execution during performance in youth sport. The purpose of this study was to examine differences in cognitive and skill execution components of game performance in young baseball players (N = 159) with varying levels of expertise. Three levels of expertise (low-, average-, and high-skilled players) were identified at each age level (7, 8, 9, and 10 years of age). Game performance was videotaped, and measures of skill execution (throwing accuracy, throwing force, fielding, catching, batting average, and batting contact) and cognitive components (positioning, decisions) were developed from observational analysis. The results indicated that baseball skill execution during game play maximally discriminated expertise levels.

Somatic comparisons of urban and rural Russian boys, ages 6, 9, and 15 years, living in St. Petersburg and surrounding areas.

Somatic data were collected during September 1991 on 280 males, ages 6, 9, and 15 years, residing in urban St. Petersburg, Russia, and in rural regions surrounding the city. Comparisons are made between urban and rural groups for measures of body size and form, skinfold thicknesses, body mass index (BMI), and estimated arm muscle area (ARM). The data were analyzed in 2 (urban-rural) × 3 (age) analyses of variance, with an alpha level of P < 0.05. Age differences were evident for all measurements. A significant main effect for urban-rural was found for stature, lower limb height, and calf girth; differences approached significance (P < 0.07) for body weight and sitting height. Urban children were larger than rural children in stature, sitting height, lower limb height, calf girth, and body weight. The interaction was nonsignificant. Urban and rural boys did not differ on measures of body form. Similar means were obtained for the sum of skinfolds, the BMI, and ARM in urban and rural boys. Compared with data collected more than a century ago, present-day 15-year-olds are 22 cm taller. It has often been suggested that living in an urban environment provides greater access to the amenities of life than living in a rural area. Although these amenities are difficult to observe differences do exist and the secular trend continues. © 1994 Wiley-Liss, Inc.

Body weight and thickness of skin and subcutaneous tissue on black boys age 9 years measured during 1983-1985 in Nigeria and the U.S.A.

Between 1983-1985 somatic data were collected on 631 Black boys age nine years drawn from Ibo, Yoruba, and United States black ethnic groups living in urban and rural locations. On urban-rural subgroups, measures of body weight and skin-fat thickness were analyzed for central tendency and variability. On each of the ethnic-regional subgroups studied, the distribution of measures for each variable is, to some extent, skewed positively. United States urban Black boys exceed their Nigerian rural age-sex peers by 6.6 kg in body weight and by 0.6 cm and 0.7 cm in skin-fat thickness on the abdomen and at the back of the arm. The thirtieth percentile of the United States urban distributions for both skin-fat sites was higher than the seventieth percentile of the Nigerian rural and urban distributions.

Comparisons of body size and form among ethnic groups of United States college men.

Original data were collected during 1979-1982 on 199 American Black and 99 American White college men attending the University of South Carolina. Statistics from these data are presented for 11 measures of body size, 6 measures of body form, and 5 measures of skinfold thickness and body composition. Each variable is described for a) the total samples of South Carolina Black and White college men, and b) three more homogeneous subgroups of college men designated Afro-Black, Afro-Black/Amerind, and Northwest European White. University of South Carolina male students are compared with other groups of United States college men and Selective Service registrants studied during the 1940's and 1950's. It is found: means for standing height of men having Afro-Black and Northwest European White ancestries exceeded the mean for standing height of peers with mixed Afro-Black/Amerind ancestry, lower limb height in percentage of sitting height, on average, was greater for Black college men than for White peers and means for body weight and standing height were higher on South Carolina Black and White college men measured during 1979-1982 than on college men measured in Kansas during the 1940's, and United States Selective Service registrants measured during the 1950's.

Skin color comparisons among ethnic groups of college men.

Reflectance readings of skin color were taken on the medial aspect of the left upper arm. The subjects were United States college men between ages 18 and 27 years attending the University of South Carolina. Using the DSL 99 Reflectance Spectrophotometer, readings were obtained under controlled conditions at five settings (601, 603, 605, 607, 609). Ethnic groups studied included young men of 1) Northwest European White ancestry, 2) West African Black ancestry, and 3) Afro-Black/Amerind ancestry. Means and variability statistics serve to describe the skin color distributions. Means were near 12 and 32 for filters 601 and 609 on men of West African Black ancestry, with corresponding means near 36 and 64 on men of Northwest European White ancestry. There was no overlapping of comparable frequency distributions from these two ethnic groups. Significance tests at P = .01 allowed acceptance of the hypothesis that skin color on the medial arm surface was darker for young men of Afro-Black ancestry than for those of 75% Afro-Black ancestry and 25% Amerind ancestry. Means from original data were compared with means from earlier studies on black and white males in Africa, America, and Europe.

Somatic findings at age 9 years on three ethnic groups of Nigerian urban and rural boys.

Somatic data were collected in 1983 on 577 Nigerian boys age 9 years drawn from Ibo, Yoruba, and Hausa ethnic groups living in urban and rural locations. On each subgroup, measures of body size, body form, and body composition were analysed for central tendency and variability. From urban samples, means for standing height and body weight were highest on Ibo boys, intermediate on Yoruba boys, and lowest on Hausa boys. Ibo urban boys, on average, were larger than their rural peers by 5.9 cm in standing height, 3.3 kg in body weight, and near 1.5 cm in shoulder width, arm girth, and calf girth. From pooled urban and rural subgroups, calf girth relative to lower limb height was near 40% on Ibo boys, 39% on Yoruba boys, and 38% on Hausa boys. From the three ethnic groups combined, means for thickness of skin and subcutaneous tissue on the arm and abdomen were higher on urban than rural boys. Composite means for 494 Nigerian Ibo and Yoruba urban and rural boys were lower than means for 208 United States Black boys measured during 1974-1977 in Richland County, South Carolina, by 1.7 cm in standing height, 3.0 kg in body weight, and near 1.5 cm in arm girth and calf girth.

Body size, body form, and nutritional intake of Black girls age 9 years living in rural and urban regions of eastern North Carolina.

Anthropometric and dietary data were obtained on 78 rural and 66 urban Black girls age 9 years residing in eastern North Carolina. Direct measures were taken of standing height, sitting height, upper limb length, arm girth, calf girth, and body weight. Body form indices were derived for arm girth in percentage of upper limb length, calf girth in percentage of lower limb length, and lower limb length in percentage of sitting height. Intakes of protein and calories were estimated from 24-hour dietary recall protocols. Rural girls, on average, had shorter upper and lower limbs than urban girls. The Recommended Dietary Allowance (RDA) for protein intake was met by almost all subjects. More than 60% of both rural and urban girls were below the RDA for calorie intake, and about 40% below the RDA for vitamin A intake.

Early seriatim research on human somatic growth.

Biological knowledge is synthesized from human longitudinal data on individuals measured between 1759 and 1915. The variables treated are stature, body weight, head girth, and chest girth. Seriatim records are assembled from early studies in Austria, Belgium, England, France, Germany, Russia, Switzerland, and the United States. Analyses are made for somatic size and gain during infancy, childhood, adolescence, and the postnatal span from birth to early adulthood. Findings pertain to differences among individuals during small and large portions of ontogeny, sex differences in body dimensions and growth rates, and differences among variables in the pattern of size-on-age curves for the period between birth and early adulthood.

Body size and form of children of predominantly black ancestry living in West and Central Africa, North and South America, and the West Indies.

Stature, sitting height, hip width, arm and calf circumferences and body weight have been measured in black children of Richland County, South Carolina. Lower limb height and three indices of body shape were obtained from the measurements. Sample size exceeded 200 for each of five age-sex groups representing girls and boys aged 6 years, girls and boys aged 9 years, and boys aged 11 years. Comparisons are made with findings from previous research on children of predominantly black ancestry living in west and central Africa, the West Indies, and North, Central and South America. Black children of Richland County measured during 1974--77 are taller than black children studied since 1960 in Angola, Chad, Ghana, Liberia, Nigeria, Senegal, Uganda, Anguilla, Barbados, Cuba, Guyana, Jamaica, Nevis, St. Kitts, St. Vincent, and Surinam. Children of well-to-do black families in Accra and Ibadan are no taller or heavier than black children of Richland County taken without regard to socio-economic status. In hip width, averages for Richland County black children are larger than those for children of the Hutu and Yoruba tribes; in arm girth they are larger than children of the Hutu and Tutsi tribes. Age changes and group differences are reported for hip width relative to lower limb height, and lower limb height relative to sitting height. During childhood, the hip/lower limb index decreases, and the lower limb/sitting height index increases. Almost identical hip/lower limb indices characterize black populations in Africa, Cuba, and the United States.

Body size and form of black and white female youths measured during 1974-1975 at Columbia, South Carolina.

From original data at age 13 years on 386 North American females (201 black and 185 white), statistics are presented for 10 somatic variables. The 2 ethnic groups yield similar means for standing height, arm girth, and leg girth; the black females, contrasted with their white peers, are shorter in sitting height, longer in lower limb height, and narrower in hip width. The Columbia subjects are compared with black and white females studied in North America several decades ago, and with black and white females studied recently in other parts of North America and in Australia, Europe, Africa, and the Lesser Antilles.

Comparative findings on the skelic index of black and white children and youths residing in South Carolina.

This paper pertains to one facet of human body form, the relation of lower limbs to stem as quantified by the skelic index (lower limb height x 100/sitting height). The subjects were North American black and white pupils measured during 1974-1975 at elementary and high schools in Columbia, South Carolina. Females were measured at ages 9 and 13 years, males at ages 11 years and 15 years. At each childhood and adolescent age studied, skelic index means were considerably higher for the black than for the white pupils. Standard deviations and distances between spaced percentiles showed that variability of the skelic index at a given age was similar for white and black school pupils of South Carolina. Supplementary means for components of the skelic index indicated (1) black children and youths were shorter in sitting height than their white age peers, and (2) white children and youths were shorter in lower limb height than their black age peers. The skelic index of both ethnic groups increased between late childhood and mid-adolescence.