Published on

Published in: Health & Medicine, Technology
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. Physical Activity Play: The Nature and Function of a Neglected Aspect of Play Author(s): A. D. Pellegrini and Peter K. Smith Source: Child Development, Vol. 69, No. 3 (Jun., 1998), pp. 577-598 Published by: Blackwell Publishing on behalf of the Society for Research in Child Development Stable URL: http://www.jstor.org/stable/1132187 Accessed: 13/05/2009 19:07 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=black. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact support@jstor.org. Blackwell Publishing and Society for Research in Child Development are collaborating with JSTOR to digitize, preserve and extend access to Child Development. http://www.jstor.org
  2. 2. Child Development,June 1998,Volume 69, Number3, Pages 577-598 Physical Activity Play: The Nature and Function of a Neglected Aspect of Play A. D. Pellegrini and Peter K. Smith In this review, we considerthe natureand possible developmentalfunctionsof physical activityplay, defined as a playful contextcombinedwith a dimension of physicalvigor. We distinguish 3 kinds of physical activity play, with consecutiveage peaks:rhythmicstereotypiespeaking in infancy,exerciseplay peaking during the preschoolyears, and rough-and-tumble play peaking in middle childhood.Genderdifferences(greaterpreva- lence in males) characterizethe latter 2 forms. Functionis considered in terms of beneficialimmediate and deferred consequences in physical, cognitive, and social domains. Whereasmost theories assume that chil- dren's play has deferredbenefits, we suggest that forms of physical activity play serve primarilyimmediate developmental functions. Rhythmicstereotypiesin infancy are hypothesized to improve control of specific motor patterns.Exerciseplay is hypothesized to functionprimarilyfor strengthand endurancetraining;less clear evidence exists for possible benefits for fat reductionand thermoregulation. addition, there may be In benefitsof exerciseplay that we hypothesizeto be largelyincidentalto its playful or physicalnature. cognitive play has a distinctivesocial component;we hypothesizethat it servesprimarilydominance Rough-and-tumble functions;evidence for benefits to fighting skills or to emotionalcoding are more equivocal.Furtherresearch is indicated, given the potentially importantimplicationsfor children'seducation,health, and development. INTRODUCTION physical activity, and even for aspects of social orga- nization and social skills. Physical activity play may, Over the past 30 years, the study of children's play in some senses, matter psychologically. has been a popular topic of scientific inquiry (see the In this review, we discuss the definition of physi- chapter on play in the fourth edition of the Manual cal activity play, and age and gender trends; we then of ChildPsychology;Rubin, Fein, & Vandenberg, 1983). consider the evidence regarding its functional bene- Pretend play is the aspect of children's play most fits. thoroughly studied (see Fein, 1981). Indeed, the para- digmatic study of young children's play has probably been the study of children's symbolic use of play ob- WHAT IS PHYSICAL ACTIVITY PLAY? jects in a developmental progression (e.g., McCune, GENERAL DEFINITIONAL ISSUES 1995). Both child developmentalists and animal ethologists Yet these analyses ignore some of the most com- agree that play behavior is enjoyable, and that play- mon forms of play, as well as some basic theoretical ers, typically children or juveniles, are concerned assumptions regarding the functions of play. Chil- with means over ends, and that the activity appears dren's play often has a vigorous physical component, to be quot;purposeless,quot; or to occur for its own sake and thus it may variously be called physical activity (Martin & Caro, 1985; Rubin et al, 1983; Smith & Voll- play, locomotor play, or exercise play. Much of chil- stedt, 1985). Physical activity play, specifically, may dren's physical activity can be seen as playful in the involve symbolic activity or games with rules; the ac- sense that it is minimally constrained by adult de- tivity may be social or solitary, but the distinguishing mands. Adults, however, often show some ambiva- behavioral features are a playful context, combined lence toward children's high levels of physical activ- with what Simons-Morton et al. (1990) describe as ity. This ambivalence may also be reflected in the moderate to vigorous physical activity, such that relative paucity of research on children's physical ac- metabolic activity is well above resting metabolic tivity generally (Pellegrini & Smith, 1993; Welsh & rate. Paradigm examples of physical activity play in- Labbe, 1994), and on physical activity play and clude running, climbing, chasing, and play fighting, rough-and-tumble play in particular (Humphreys & Smith, 1984). Yet physical activity levels may be im- portant, not only for physical development, but also @ 1998 by the Society for Research in Child Development, Inc. perhaps for cognitive performance subsequent to All rights reserved. 0009-3920/98/6903-0002$01.00
  3. 3. Child Development 578 these behaviors is probably controlled by general the latter being a component of rough-and-tumble neuromuscular maturation. play (R & T). Stereotypic behaviors tend to peak during the The criterion of purposelessness in the definition midpoint of the first year of life; at 6 months, some of play seems to present a logical problem when play infants spend as much as 40% of a 1 hr observational is also considered to be functional (Martin & Caro, period in stereotypic behavior (Thelen, 1980). After 1985). How can play simultaneously serve no pur- this point, the behaviors gradually disappear from pose and serve a developmental function? One way to resolve this problem is to consider play as serving normal children's behavioral repertoires (Thelen, 1979). Across the first year of life, infants spend 5.2% minimal immediate functions during childhood, of their time in stereotypic behaviors (Thelen, 1980). with benefits deferred until maturity. Alternatively, play may serve immediate functions about which Some early parent-infant interactions probably pro- players and others are unaware. We will hypothesize vide other physical play opportunities. For example, Roopnarine, Hooper, Ahmeduzzaman, and Pollack's about such functions. We first consider age and gen- (1993) examination of play between parents and 1- der trends, because these may indicate different types year-old infants in India suggests that play, such as of physical activity play that may have different func- tossing the infant in the air and bouncing on the knee tional significance (Byers & Walker, 1995). (but also including R & T), accounted for 13% of all play, whereas object play accounted for 80%. Simi- AGE AND GENDER TRENDS IN PHYSICAL larly low rates of American parent-infant physical ACTIVITY PLAY play (or vestibular stimulation) were reported by Thelen (1980). Studies relevant to age and gender trends for physi- cal activity play are presented in Table Al of the Ap- Exercise pendix. Play By exercise play we mean gross locomotor move- ments in the context of play. The distinguishing fea- Age Trends ture of this play is its physical vigor; it may or may Play generally follows an inverted-U develop- not be social, but the distinctively specialized social mental course: It begins in early infancy, peaks dur- form of R & T is discussed later. ing childhood, then declines during adolescence, and Exercise play in this sense can start at the end of all but disappears by adulthood (Byers & Walker, the first year. It can be solitary or with parents or 1995; Fagen, 1981; Rubin et al., 1983). However, the peers. In fact, much of the research on parent-infant trends in physical activity play in humans appear to play does not distinguish between exercise play and show three successive peaks, reflecting three types of R & T, but appears to be describing quot;rough physical play, probably with different functions. We designate playquot; (Carson, Burks, & Parke, 1993; Roopnarine et these as (1) rhythmic stereotypies, (2) exercise play, al., 1993), which we consider under R & T later. Low and (3) R & T. We discuss each in turn. rates of American parent-infant physical play have been reported by MacDonald and Parke (1986), with rates peaking at around 4 years of age. A few cases Stereotypies Rhythmic of infant exercise play without parents have been re- ported. Konner (1972), for example, observed that a Although most studies in the infancy literature re- Botswana foraging group encouraged infants to late to the ontogeny of symbolic play with parents chase after and catch large insects. (e.g., Bornstein & Tamis-LeMonda, 1995) and sensori- motor exploration / play (e.g., Ruff & Saltarelli, 1993), As we move to the preschool period, greater inci- dences of exercise play are reported. As was the case there is limited evidence documenting infants' physi- in infancy, most of the peer play literature for this cal activity play. Thelen's (1979, 1980) longitudinal period focuses on pretend play, not physical activity study of infants' quot;rhythmical stereotypiesquot; during play. Where the latter is reported, it is often in the the first year of life provides basic and important de- form of R & T, which tends to co-occur with pretend scriptive information. Rhythmical stereotypic behav- during this period (Pellegrini & Perlmutter, 1987; iors are similar to our definition of physical activity Smith, 1973; Smith & Connolly, 1980). In a few stud- play to the extent that they are gross motor move- ies, quot;gross motorquot; play other than R & T is reported, ments, quot;and it is difficult to ascribe goal or purpose sometimes occurring alone, sometimes with peers to those movementsquot; (Thelen, 1979, p. 699); examples (rather than with parents). include body rocking and foot kicking. The onset of
  4. 4. Pellegrini and Smith 579 most children engaged in one or two long (>10 min) Exercise play seems to increase from the toddler to preschool period and then declines during the pri- MVPAs/day. In general, then, exercise play is quite common in mary school years, with a likely peak at around 4 to early/middle childhood, and appears to peak in the 5 years (Eaton & Yu, 1989; Routh, Schroeder, & O'Tu- preschool and early primary grades, although more ama, 1974). Specifically, for 2-year-olds, Rosenthal evidence is certainly needed to clarify exactly when (1994) reports that it accounts for about 7% of behav- ior observed in day-care settings. For children 2 to 4 the age peak occurs. years of age, Field (1994) reports physical activity play accounting for 10% of all day-care behavior. Play Rough-and-Tumble Similarly, Bloch's (1989) observational study in Sene- gal found that gross motor activities accounted for Rough-and-tumble play refers to vigorous behav- iors such as wrestling, grappling, kicking, and tum- 11% and 13% of children's play in the home at 2 to bling that would appear to be aggressive except for 4 years of age and 5 to 6 years of age, respectively. In two ethological studies in British nursery the playful context; chasing is sometimes included within this definition, but here we restrict it to the schools, using a variety of samples, McGrew (1972) former contact behaviors. Whereas exercise play may and Smith and Connolly (1980) observed children's or may not be social, R & T is necessarily so. behavior at a micro-analytical level. In McGrew's The earliest cases of children's R & T play are sup- sample, with a mean age of 49.2 months, approxi- ported by a parent, often the father in the case of mately 20% of children's activity was physically vig- rough physical play (Carson et al., 1993; Roopnarine orous, such as run, flee, wrestle, chase, jump, push and pull, lift, and climb. Similarly, in Smith and Con- et al., 1993). As reviewed earlier, rates of such play are low. At around 4 years of age, R & T accounts for nolly's (1980) sample, with a mean age of 43.3 months, vigorous activities, such as run, chase, and about 8% of observed parent-child behavior (Jacklin, climb (but also including R & T), accounted for 21% DiPietro, & Maccoby, 1984). Rough-and-tumble play with peers is more thor- of their behavior. oughly documented; its frequency follows an in- As children move into primary school, a decline in physical activity is witnessed. For children aged 6 verted-U developmental curve. For preschool chil- to 10 years, quot;exercise playquot; accounted for only 13%of dren, it accounts for approximately 3%-5% of play behavior (Pellegrini, 1984); at 6 to 10 years, it ac- all outdoor behavior observed during school recess periods (Pellegrini, 1990). This relative decrease in counts for 7%-8% of recess behavior (Boulton, 1992; Pellegrini, 1988); and during the period from 7 to 11 play might be underestimated, however, because the years, for about 10% (Humphreys & Smith, 1987). At primary school observations occurred on school 11 to 13 years it falls to 5% (Boulton, 1992; Pellegrini, playgrounds, rather than in classrooms, unlike most 1995a), and there is a further decrease to only 3% at studies of preschoolers; the relative spatial density of 14 years (Pellegrini, 1995b). classrooms, compared to playgrounds, inhibits gross These studies used similar definitions and meth- motor activity (Smith & Connolly, 1980). odologies, so that this age curve can be advanced It will be important for our later argument to dem- with reasonable confidence. Rough-and-tumble play onstrate that during the preschool/primary school appears to increase through the preschool and pri- years children engage in substantial amounts of exer- mary years and peak in the later primary years, cise play. Blatchford (1996) described the general lev- around 8 to 10 years, just prior to early adolescence; els of English primary school children's activity on this appears to be a distinctively later peak than that the school playground and found that most (60% of for exercise play, provisionally described as being at the children) are engaged in some form of physically 4-5 years. active play or games during their daily break times, which lasted between 65 and 75 min. What about physical activity outside the school Summary of Age Trends context? Simons-Morton and colleagues (1990) stud- In summary, forms of physical activity play are ied children aged 9 and 10 years, using children's quite common in childhood. In primary schools, most self-reported frequency of moderate to vigorous children engage in active play during their daily physical activity (MVPA) over 3 days. Major sources break times; further, levels of physical activity play of MVPA were running, walking fast, games and are moderate for most children when they are out sports, and cycling. MVPAs generally were slightly of school. An analysis of age trends suggests three more common before or after school (2.3/day) than successive inverted-U curves describing three differ- during school (1.6/day). Throughout the whole day,
  5. 5. 580 Child Development ent forms of physical activity play. Rhythmic stereo- many other mammalian species (Meaney, Stewart, & typies peak in infancy, at around 6 months of age; Beatty, 1985; Smith, 1982). This is true for parent- exercise play peaks during the preschool years, ac- child rough play (Carson et al., 1993; Roopnarine et counting for up to 20% of observed school recess be- al., 1993) and for peer play (Humphreys & Smith, havior, and declines during the primary school years, 1984; Pellegrini, 1989a); this gender difference is accounting for about 13% of observed behavior. more marked for contact R & T than for play chasing Rough-and-tumble increases during the late pre- (Smith & Connolly, 1980). school and early primary school years, accounting for Differences in boys' and girls' initiation of and re- about 5% of observed recess behavior, peaks in later sponse to R & T may be implicated in these gender primary years at around 10%, and then declines dur- differences. Both the animal and child literatures of- ing early adolescence, accounting for less than 5% of ten show males' higher rates of initiation of R & T play. We postulate that these successive age peaks bouts and females' higher withdrawal from bouts reflect different forms of play with different func- (Fabes, 1994; Meaney et al., 1985; Pellis, Field, tions. Smith, & Pellis, 1996). Females may withdraw from R & T initiations as they react differently from males to tactile stimulation of the sort that characterizes Gender Differences R & T (Meaney et al., 1985; Pellis et al., 1996). The physical vigor and roughness typical of boys' play Rhythmic Stereotypies groups seem to be important factors for girls segre- No sex differences are reported in the incidence of gating themselves from boys' play groups (Fabes, rhythmic stereotypies. Thelen (1980) compared rates 1994; Maccoby, 1986). for 10 male and 10 female infants; these averaged 35.1 and 34.4 bouts per hour, respectively, a very small Causal Factors in GenderDifferences and nonsignificant difference. Gender differences appear to be absent in rhyth- mical stereotypies, but appreciable for both exercise Exercise Play play and R & T. Hypotheses about the functions of Males tend to engage in exercise play at higher play must take account of such gender differences rates than females. Eaton and Enns's (1986) meta- and the causation of such differences. analysis of 90 studies of gender differences in motor Hormonal influences on play have been impli- activity level reported a significant difference in favor cated in gender differences in R & T. Hormonal in- of males, with the effect size tending to increase from fluences typically center around the effects of en- infancy to mid-adolescence. Part of this gender differ- dogenous and exogenous androgens on neural ence may be due to differential maturation rates. Ea- organization and behavior (Meaney et al., 1985). Nor- ton and Yu (1989) found that relative maturity (per- mal exposure to androgens during fetal development cent of estimated adult height attained) interacted predisposes boys, compared to girls, toward physical with gender, being negatively related to activity activity and R & T. Excessive amounts of these male level, with girls being both less active and more phys- hormones are hypothesized to quot;masculinizequot; fe- ically mature than boys. males' play (Collaer & Hines, 1995). The experimen- In these studies, R & T was probably included tal literature involving mice, rats, hamsters, and with exercise play; although R & T takes up a smaller monkeys supports the androgenization hypothesis percentage of time through the early primary years (Collaer & Hines, 1995; Quadagno, Briscoe, & Qua- (see discussion of age trends), some of the gender dif- dagno, 1977). For obvious ethical reasons, the effects ference in exercise play may be attributable to the of androgens on human behavior can only be studied well-documented gender difference in R & T (next through natural experiments, where fetuses receive section); it will be important for future research to abnormally high levels of these male hormones be- delineate gender differences with an unconfounded cause of genetic defects (e.g., Congenital Adrenal Hy- measure of exercise play. perplasia [CAH]) or difficulties during pregnancy (e.g., where mothers take synthetic progestins). Most human studies of CAH support the andro- Play Rough-and-Tumble genization hypothesis. These studies typically have Males exceed females in frequency of R & T in vir- used questionnaire methodology to ask parents or tually all cultures that have been examined (DiPietro, children about their preferences for various activities, including physically active sports and R & T. The fre- 1981; Humphreys & Smith, 1984) and also among
  6. 6. Pellegrini and Smith 581 quently cited research of Money and colleagues (e.g., on the long-held emphasis among child develop- Money & Ehrhardt, 1972) has shown that andro- mentalists on developmental continuity (Bateson, genized girls are more quot;tomboyishquot;: They prefer 1981; Gomendio, 1988; Kagan, 1971). Bateson's (1976) male activities more than do nonandrogenized girls. metaphor for the deferred-benefit view of play is Using observations of toy preferences in CAH chil- quot;scaffoldingquot;: Play functions in skill assembly, and dren compared to controls, Berenbaum and Snyder then is disassembled when the skill is mastered. (1995) found that CAH girls showed greater prefer- Alternatively, play may be viewed not as an in- ence for boys' toys and activities. complete or imperfect version of adult behavior, but Although Hines and Kaufman (1994) found no in- as having immediate benefits during childhood. This crease of R & T in CAH girls, the children were ob- quot;metamorphicquot; (Bateson, 1976) view posits that play served for only one 12 min session in an experimental and its consequences are unique to the niche of child- room of undisclosed size-conditions that may have hood, and that later benefits are not necessary for its inhibited children's exhibition of normal behavior, explanation (Bjorklund & Green, 1992; Gomendio, including R & T. 1988; Pellegrini, Horvat, & Huberty, 1998). This view Socialization interacts with hormonal events to af- is consistent with recent discussions suggesting that fect gender differences (Ehrhardt, 1984; Fabes, 1994; play occurs at specific periods during which develop- Maccoby, 1986; Meaney et al., 1985; Quadagno et al., ment may be modified (Byers & Walker, 1995; 1977). Beginning with interactions with their parents, Thelen, 1979). Accordingly, the previously discussed boys and girls are socialized into different, and often age distribution of physical activity play may be use- segregated, worlds that tend to reinforce these gen- ful in evaluating functional hypotheses. der differences (Maccoby, 1986; Meaney et al., 1985). Different forms and dimensions of physical activ- For example, fathers spend more time with their sons ity play may serve specific developmental functions than with their daughters (Parke & Suomi, 1981), and (Gomendio, 1988; Smith, 1982). We discuss the func- when with their sons, they engage in physically vig- tion(s) of physical activity play, considering the age orous play (Carson et al., 1993; MacDonald, 1993; trends and gender differences summarized above. MacDonald & Parke, 1986). That girls are more We also consider both the dimension of physical ac- closely supervised by parents and teachers (Fagot, tivity itself and the dimension of social participation 1974, 1994) may further inhibit their physically vigor- that distinguishes exercise play from R & T. Al- ous behavior (Maccoby, 1986). though some authors list up to 30 possible functions for play (Baldwin & Baldwin, 1977), certain functions (physical training, cognitive, and social) are most FUNCTIONS OF PHYSICAL ACTIVITY PLAY commonly advanced. Appendix Table A2 summa- In his discussion of ways in which behavior can be rizes the extant studies, by function. explained, Tinbergen (1963) described the quot;Four As a first step in establishing the functional impor- Whysquot; of behavior as being immediate causation, de- tance of physical activity play during childhood, velopmental history, immediate function, and ulti- we present evidence from a small number of play- mate function in terms of evolutionary history. For deprivation studies, either natural or experimental. the purposes of this article, we do not consider func- These suggest that a lack of opportunity to engage tion in its quot;ultimatequot; sense (Hinde, 1980, p. 102), that in physical activity play leads to compensation later, is, in terms of survival or reproductive success over concluding that play is of functional benefit. succeeding generations. To directly address ultimate In Thelen's (1980) study of rhythmic stereotypies function, a more wide-ranging analysis would be in the first year of life, infants who engaged in a lot necessary, to an extent that would necessarily be very of these spontaneous physical activities when given the opportunity were those observed to receive less speculative given the limited evidence available. In- stead, we consider function in terms of the quot;benefi- vestibular stimulation from caregivers and those who were more often restricted in natural movements cial consequencesquot; of the behavior to the individual (Hinde, 1980). These consequences can be either im- (e.g., placed in infant seats). Thelen (1980, p. 148) con- mediate or deferred. cluded that quot;deprivation of active as well as passive For almost a century, the dominant view in child movement may ... promote stereotypy.quot; development (Groos, 1898, 1901) has been that play Three sets of field experiments have looked at dep- has deferred benefits. That is, during the period of rivation of physical activity play during childhood; extended childhood, children engage in play to learn in these, although exercise play was the primary out- come variable, R & T would also have been included. and practice those skills necessary to be functioning adult members of society. This assumption is based Smith and Hagan (1980) studied English preschool
  7. 7. 582 Child Development are based on the systematic onset of specific behav- children (3-4 years) who were deprived of vigorous iors and their co-occurrence with milestones of motor exercise by varying the amount of time they re- mained in their classrooms engaged in sedentary development. Thelen found that the individual be- haviors appeared during a restricted period; onset seatwork. After deprivation periods, they played out- was not randomly distributed. This pattern, she ar- doors. On the long, compared to short, deprivation days, children's play was more vigorous in the imme- gued, is indicative of neuromuscular maturation. To support this claim further, she presented significant diate postdeprivation period. correlations between the age of onset of stereotypic Utilizing a similar deprivation paradigm with groups (e.g., legs, arms, hands and knees) and the American primary school children (5-9 years), Pelle- age of passing items from the Bayley Scales of Infant grini and colleagues (Pellegrini & Davis, 1993; Pelle- grini, Huberty, & Jones, 1995) replicated Smith and Development reflecting neuromuscular, not cogni- tive, development. Rhythmic movements of given Hagan's results: Long, compared to short, depriva- tion periods resulted in higher levels of physical ac- body systems appear to increase just before the infant tivity. Deprivation, however, interacted with gender achieves voluntary control of that system. We postulate that infants' rhythmic stereotypies of the child; boys, compared to girls, were especially are primarily functional for the immediate benefits active after long deprivation. of improving control of specific motor patterns. The These results support the following generaliza- tion: If children are deprived of opportunities for correspondence between the ages at which these movements occur and cerebral development sug- physical activity play, they will, when given the op- portunity to play, engage in more intense and sus- gests that, initially, rhythmic stereotypies may be manifestations of immature sensorimotor integra- tained bouts of physical activity play than they would have done if not so deprived. This generaliza- tion. Play may modify or eliminate irrelevant syn- apse formations; with maturation, these patterns are tion, in turn, suggests that physical activity play is used in more goal-directed ways (Byers & Walker, serving some developmental function(s) such that a 1995; Thelen, 1979). Such a hypothesis is consistent lack of it leads to compensation. with the lack of gender differences in these behaviors, In the remainder of this section, we first consider because there is no reason to suppose that control of physical training (and related) functions of rhythmi- motor patterns at this very basic level of generality cal stereotypies and of exercise play. We then exam- is more important for boys than for girls. ine possible cognitive functions of exercise play. We assume that any physical training functions and cog- nitive functions of exercise play would also apply to ExercisePlay R & T, which has some of the same physical compo- With the onset of locomotion, another develop- nents. We then examine different hypotheses for so- mental course may begin, as evidenced by the corre- cial functions for R & T only, because this is the form spondence between exercise play and muscle differ- of physical activity play that is characteristically and entiation, strength, and endurance. Brownlee (1954) necessarily social. was the first to propose that animal play was related to juvenile muscle development. Fagen (1976) ex- Physical Training tended this argument by proposing deferred benefits of exercise play for motor training, specifically, mus- Both rhythmic stereotypies and exercise play seem cle strength, general cardiopulmonary functioning, to have physical training benefits. and metabolic capacity. He suggested that the forms of exercise play, often involving varied, interrupted, Rhythmic Stereotypies and repeated use of muscle groups, as well as whole- body activities, would be well suited to these de- Activities such as waving the arms and kicking ferred benefits. Byers and Walker (1995), in a thor- peak at around 6 months of age. The onset of these ough review of the animal play and motor training actions is probably controlled by general matura- literatures, evaluated the issue of immediate or de- tional processes, which correspond to neuromuscular ferred benefits of exercise play for three aspects of maturation (Field, Ting, & Shuman, 1979). Thelen motor training: endurance, strength, and skill and (1979), in her naturalistic longitudinal study of in- economy of movement. They suggest that exercise fants' rhythmic stereotypies, suggests that this is a play may improve skill and economy of movement sensitive period in neuromuscular development, due to the effects of exercise on muscle fiber differen- similar to the argument of Byers and Walker (1995). tiation and cerebellar synaptogenesis. They present Her functional inferences about physical activities
  8. 8. Pellegrini and Smith 583 developmental data from house mice, rats, cats, and functional inferences, they do provide some evidence in a very restricted literature. This evidence supports giraffes and conclude that physical activity in the ju- the hypothesis that children who habitually engage venile period, beginning in the early postnatal period in vigorous games and sports show immediate bene- and declining at mid-lactation, is a sensitive period fits in terms of being fitter than children who do not. in the development of these functions. Exercise play Smoll and Schutz (1985) studied 3,000 students in during this period has a lasting effect on subsequent British Columbia aged 9, 13, and 17 years. Athletes economy and skill of movement. emerged as significantly fitter than nonathletes on all In human children, exercise play may help shape physical fitness tests. This was true for both boys and the muscle fibers used in later physically vigorous girls. Differences between athletes and nonathletes activities. This could improve the economy and skill were small at 9 years, but increased substantially by of movement along the lines suggested by Byers and 13 and 17 years. This would be consistent with physi- Walker in other species, although we know of no di- cal training effects of such participation, although rect evidence for this. However, the evidence sug- as selective participation other explanations-such gests that endurance and strength may be developed and dropout-are also possible. through sustained exercise bouts. The age course of Relatedly, Lussier and Buskirk (1977) examined exercise play also corresponds to the growth of arm the effects of a 12 week endurance training program and leg muscles and bones during the preschool pe- (distance running) on 8- to 12-year-old boys and girls. riod (Tanner, 1970). Exercise play during the school Training decreased heart rate during submaximal years and beyond might continue to benefit muscle workloads and increased maximum oxygen uptake. and bone remodeling and strength and endurance Other studies of endurance training have had posi- training; physiological effects have been observed tive immediate results, and reviews (e.g., Rowland, into adulthood in numerous species (Byers & Walker, 1985; Simons-Morton, O'Hara, Simons-Morton, & 1995). Parcel, 1987) concur in concluding that regular, high- Byers and Walker (1995, p. 29) were skeptical that intensity training can improve cardiorespiratory exercise play functions to support strength or endur- ance. They concluded that quot;in many species, it is un- functioning. The evidence presented thus far suggests that chil- likely that play is a form of endurance or strength dren are given opportunities for exercise play that are training because play bouts are too brief to prompt probably adequate for endurance training; but before such benefits of exercise.quot; They suggested that chil- firm conclusions are made, even for the preschool dren would need to engage in daily bouts of exercise and primary school periods, more research is needed play, lasting 1 hr, 4 to 5 days per week, to increase to document the intensity and duration of exercise endurance significantly. However, based on previous play. Further, we do not know, beyond the preschool data from research on preschool and primary school period, the extent to which vigorous physical activi- children's playtime and activities out of school, we ties are playful, per se, or not. This remains an impor- postulate that children at these ages may well engage tant task for future research. in exercise play at levels meeting these criteria. Etho- In summary, exercise play, in the preschool years logical preschool studies discussed above show that especially, seems sufficiently frequent that it can 20% of children's behavior during free-play periods, serve an immediate function for endurance and usually lasting the whole morning, was classified as strength training. It may also improve skill and econ- vigorous (McGrew, 1972; Smith & Connolly, 1980). omy of movement, although specific evidence for this Although some primary school children's play op- is lacking. This hypothesized set of functions is con- portunities may be more limited, due to school regi- sistent with the age curve for exercise play (Tanner, mens, their recess periods, typically accounting for 1970). More intriguing is its relation to the gender dif- 20-60 min / day in American schools and 65-75 min / ference observed. Strength training at least would be day in English primary schools (Blatchford, 1996), are more important for males in the quot;environment of also characterized by exercise play (Blatchford, 1996; evolutionary adaptednessquot; for fighting and hunting Pellegrini, 1990). These activities are supplemented skills (e.g., Boulton & Smith, 1992); however, it could by activities in other contexts, as children usually en- also be argued that endurance training is equally or gage in more than two physically vigorous activities more important for females (for gathering activities). daily outside of school (Simons-Morton et al., 1990). Although very speculative at present, such hypothe- Additional evidence for the role of physical activ- ses could lead to more differentiated predictions con- ity play and endurance training comes from compari- cerning gender differences in types of exercise play, sons of athletes and nonathletes. Although we recog- analogous to Silverman and Eals's (1992) differentia- nize the limitations of these comparisons for making
  9. 9. Child Development 584 hypothesis does not explain the specific age course tion of types of spatial ability in relation to gender of exercise play, nor does it explain the gender differ- differences. Two other functional hypotheses regarding the ence found. We hypothesize that thermoregulation is an incidental benefit of exercise play, and that ther- physical component of exercise play can be taken moregulation, when important, can also be achieved from the animal literature; these are the fat-reduction by other means so far as humans are concerned. hypothesis and the thermoregulation hypothesis. In summary, we postulate that exercise play func- Initial studies of physical activity play in children were theoretically framed in variants of Spencer's tions primarily to develop physical strength, endur- (1898) Surplus Energy theory, in which such play was ance, and economy of movement; there is some evi- dence to support the fat-reduction theory; and seen as a way of dissipating energy surplus to bodily thermoregulation is postulated to be an incidental requirements. Although little logical or empirical benefit of exercise play. We next examine possible support currently exists for this theory (Burghardt, 1984, 1988; Smith, 1982; Smith & Hagan, 1980), Barber cognitive functions for exercise play. (1991) develops a variant of the argument. He sug- gests that energy is not usually in short supply for Cognitive Performance and Exercise Play young mammals, and that play prevents obesity by Less obvious than the likely benefits of exercise ensuring that quot;surplusquot; energy is not stored as un- necessary fat. In particular, some young animals may play for physical development are possible effects on psychological, and especially cognitive, factors. Here need to consume large amounts of food to get enough we review whether engaging in exercise play has protein, and play can quot;burn offquot; the excess require- proximal consequences for cognitive performance. ments. In addition, play, by generating heat, may Effects on cognitive tasks might be expected from provide defense against cold exposure. These postulated functions could be applied to hu- several theoretical viewpoints; however, these theo- ries link any cognitive benefits to outcomes one step man children as well as to other young mammals. The childhood period, which involves high rates and removed from exercise play per se, namely, arousal, breaks from cognitive tasks, and sense of mastery or levels of physical activity play, also corresponds neg- atively to gains in fat (Tanner, 1970, p. 86). That is, well-being. First, exercise play can lead to heightened arousal, after 9 months of age, when play involving locomo- which might influence performance following the in- tion is increasing, fat gain has a negative velocity un- verted-U hypothesis (Tomporowski & Ellis, 1986). til 6 to 8 years of age. Although these age trends are That is, moderate levels of arousal lead to better per- consistent with Barber's hypothesis applied to hu- formance than do higher or lower levels. Alterna- man children, gender differences are not; there seems tively, increased arousal may lead to a narrowing of no reason to suppose that fat reduction should be attention to core task components (Easterbrook, more important for boys in the preschool years. The vigorous dimension of exercise play may also 1959). serve an immediate function in relation to thermo- Second, exercise play might, by breaking up cogni- tive tasks, provide spaced or distributed practice ability of individuals to regulate regulation-the rather than massed practice. In another version of their body temperatures (Burghardt, 1988). Ac- this approach, stemming from the cognitive immatu- cording to this hypothesis, children would engage in rity hypothesis, the specifically playful nature of the exercise play, which expends stored caloric energy, break could be considered important. Relatedly, ef- to raise their body temperature when the ambient fects on performance, possibly mediated by breaks temperature is low (Barber, 1991). The empirical rec- and enhanced attention, might be dependent upon ord provides some support for this claim. Studies of enhanced feelings of mastery, or of well-being, after outdoor play have found that exercise play is in- exercise play. creased by cool ambient temperatures for preschool Unfortunately, much of the available research on (Smith & Hagan, 1980) and primary school children exercise and cognitive performance is on adults. (Pellegrini et al., 1995), and low levels of exercise play Tomporowski and Ellis (1986) provided a compre- are observed in tropical climates (Cullumbine, 1950). hensive review of 27 such studies directly linking ex- Whereas exercise play might be used by children to ercise intervention-only some of which can be de- raise body temperature, nonplayful physical activity fined as exercise play-to cognitive performance. is another way in which human beings of all ages They considered effects of different types of exercise (and other mammals; Barber, 1991) can raise their (short or long duration; anaerobic or aerobic) on cog- body temperatures in cold climates. Therefore, these benefits are not limited to childhood. In addition, this nitive tasks given during and / or after the exercise.
  10. 10. and Smith 585 Pellegrini The pattern of findings is conflicting. The only con- with primary school children, Pellegrini and col- sistent trends emerged from studies of brief, high- leagues (1995) examined the relation between the level of physical activity in exercise play on the intensity anaerobic exercise (hand dynamometer, or school playground during recess and subsequent at- weight-pulling); here, moderate levels of muscular tention to standardized classroom tasks. They found exertion usually improved cognitive task perfor- no relation between post-recess attention and levels mance assessed during the exercise (e.g., participants of physical activity in recess exercise play, as mea- would grip a hand dynamometer in each hand and sured behaviorally by an indicator of caloric expendi- recall nonsense syllables). This generally inconclu- ture ranging from a resting state to a highly vigorous sive pattern of findings may be due both to inconsis- state. Attention to standardized tasks after recess, tencies across studies and to confounding factors, however, was higher than before recess. They con- such as different levels of participants' motivation to participate or different initial levels of physical fit- cluded that the break between tasks, not physical ac- tivity in exercise play per se, was responsible for the ness. Although information on children is limited, a increased attention. From this viewpoint, any break that provided an activity different from the class- large-scale study of the benefits of guided physical room activities could serve this function. activity (physical education classes) on children's school performance was conducted by Shephard and colleagues (1983; Volle et al., 1982). As part of the The Cognitive Immaturity Hypothesis Trois Rivieres project in Canada, entire primary An adaptation of the cognitive immaturity hy- school classrooms (grades 2-6) received an addi- pothesis (Bjorklund & Green, 1992; Pellegrini & tional 5 hr of physical education per week; control Bjorklund, 1997) would suggest that not only is classrooms received no physical education. Teachers apparently were aware of children's condition as- spaced or distributed practice important for attention signments, but the influence of teacher bias was and cognitive performance, but that the nature of the minimized by the administration of independent, intervening break period is crucial; and, specifically, that activity of a playful nature might be important. province-wide examinations. The academic perfor- This hypothesis holds that immaturity is not just mance of children in the experimental group was su- something to overcome, but that children's immature perior to that of the control children. The authors sug- gest that the benefits shown in this project may have nervous systems may be adapted to deal effectively with the cognitive demands they face in their daily been due either to arousal caused by the enhanced exercise or by shortening of class work time (and lives at those particular developmental periods. Spe- hence quot;spaced practicequot;) by inserting physical edu- cifically, young children have difficulty keeping ex- traneous information from entering short-term mem- cation classes (Shephard, 1983). ory store. As a result, their working memories are The latter interpretation is consistent with Steven- son and Lee's interpretation (1990) of achievement in often cluttered with irrelevant information, leaving less mental capacity for task-relevant information or Japanese, Taiwanese, and American schools. They for the execution of cognitive strategies. Younger suggested that the frequent breaks between periods children may require a greater change in activity or of intense work in Japanese schools (usually 10 min stimulus materials before they experience a release every hour) maximize children's cognitive perfor- from interference (Bjorklund, 1978); hence, a shorter mance. That children's task vigilance increases when attention span in childhood, and an inclination to the time spent on the task is distributed, rather than play, may have adaptive value. massed, is a consistent finding in the animal and hu- From this perspective, there would be a general man learning literatures (Dempster, 1988). The increase in interference when children perform a se- massed versus distributed practice literature consis- ries of cognitive tasks, regardless of the nature of tently shows few differences across age from pre- those tasks. Although one would predict, from a school to old age (Dempster, 1988). Individual differ- massed versus distributed practice perspective, that ences in children, such as quot;distractibilityquot; or changing from one type of cognitive activity to an- quot;activityquot; levels, may mediate the effectiveness of other would yield some attentional benefit, children, distributed practice regimens, however, and should be addressed in future research. especially young children, may experience a contin- ued buildup of interference with repeated perfor- It thus remains questionable whether it is exercise mance of even very different cognitive/academic play per se, rather than just a break from sustained tasks, all of which require concentration; thus, chil- classroom work, that is responsible for any increased dren may experience greater benefit from a drastic cognitive performance. In a series of experiments
  11. 11. 586 Child Development change in activity, such as is afforded by exercise childhood. Rough-and-tumble play peaks later than play at recess. exercise play, during the middle childhood period, Exercise play could be beneficial in this way, both when it accounts for about 10%of free-play behavior; because it is nonacademic and also because it is self- it then declines in adolescence, accounting for less motivated, playful, and associated with enjoyment, than 5%. This peak period co-occurs with children's self-efficacy, and mastery. The cognitive immaturity establishing social status in peer groups (Waters & hypothesis (Bjorklund, in press; Bjorklund & Green, Sroufe, 1983). 1992), as well as other theories of play (Pellis & Pellis, The second is an argument by design. Rough-and- in press; Piaget, 1962; Vygotsky, 1978), postulate that tumble play is a distinctive form of behavior. It is su- children's play is associated with a sense of mastery perficially similar to real fighting; however, it is dif- and well-being, and that this has cognitive implica- ferent in many respects and should be regarded as a tions. separate construct (Pellis & Pellis, in press). A num- On this viewpoint, the playful nature of exercise ber of distinguishing criteria have been identified by play would be important for its attentional benefits in observational and ethological research (Smith, 1989); providing a break in academic, teacher-led cognitive in addition, young children from a variety of nations tasks; especially for preschool and young elementary also consider them to be distinct (Boulton, 1993; Cos- school children, such a function is consistent with the tabile et al., 1991; Pellegrini, 1989b). That R & T and age distribution of exercise play. Once again, how- aggression are independent systems during child- ever, a gender difference would not be predicted. hood also has support from behavioral observations In summary, evidence for the direct role of exer- of children from numerous cultures showing that cise play in cognitive performance is incomplete. It R & T, at least before adolescence, is not correlated does not seem likely that any such benefits are a pri- with, and does not escalate to, aggression for most mary function of exercise play. They do not explain children (Blurton Jones, 1972; Fry, 1987; Pellegrini, the gender difference observed. In addition, the orga- 1988). Finally, the endocrinological and neural con- nized massed cognitive practice of schooling is a re- trols for fighting and for R & T appear to be different cent cultural invention, and therefore the comple- in many mammalian species (Meaney et al., 1985). mentary benefits of spaced practice provided by We review here evidence relating R & T to fighting exercise play-even if specifically related to its play- skills, to dominance functions, and to skills of emo- ful nature, as the cognitive immaturity hypothesis tional encoding and decoding. predicts-would also be recent in human history. We hypothesize that the cognitive benefits associated R & T and FightingSkills with exercise play are in fact incidental or serendipi- tous, due to the fact that it provides a playful break The most traditional view in the animal and hu- from demanding tasks. man literature (Smith, 1982; Symons, 1978) is that Thus far we have considered the benefits of the R & T functions to provide safe practice for fighting physical component of exercise play, irrespective of (and possibly hunting) skills that will be useful in its social nature. However, children often engage in later life. This hypothesis would be consistent with physical activity play with partners; and rough-and- the strong gender difference observed, if one as- tumble play (play fighting, wrestling) is a specialized sumes that fighting and hunting skills were and are form of physical activity play with a distinctive age more characteristically male activities (Boulton & curve, suggesting that it has its own functions. We Smith, 1992). It does not, however, predict the age propose that such functions will be primarily social, curve for R & T, because quot;safequot; practice of such skills because purely physical or cognitive functions of the might be especially important in adolescence, when kind reviewed earlier could be provided by exercise R & T declines. Also, there is little or no direct evi- play generally and may not require the specific forms dence linking R & T to fighting or hunting skills, in of R & T observed. We also recognize, as noted either the animal or human literature. Finally, this above, the possibility that R & T may have motor hypothesis does not predict the age changes in training benefits. quot;cheatingquot; observed in human R & T. Players quot;cheatquot; when they violate the rules of play by manip- ulating the nonserious tenor of the activity for their Social Functions and Rough-and-Tumble Play own, exploitive ends. We do not dismiss this argu- The distinct functional significance of R & T is sug- ment-indeed, we suspect that it may be a phyloge- gested by two arguments. The first is the relative and netically prior function with some remaining rele- peak frequencies with which it is observed during vance for younger children. However, we turn to the
  12. 12. and Smith 587 Pellegrini argument for dominance functions of R & T, which which are related to physical prowess, to regulate ac- cess to resources (e.g., struggling over access to a have not received the same attention but which may toy). Physical prowess, or toughness, when used in yield new insights in the case of human R & T. conjunction with more affiliative skills is an impor- tant dimension of boys' peer group status (Strayer, R & T and Dominance Relationships 1980), popularity (Pellegrini, 1995b; Vaughn & Wa- ters, 1981), and social leadership (Hartup, 1983). Dominance is defined as a dyadic, affiliative rela- Age trends in R & T are also consistent with a tionship between individuals, not in terms of one's dominance function if we consider that the immedi- aggressiveness (Hinde, 1974). Dominance hierarchies ate preadolescent period is one in which it is impor- are generally unique to specific groups and ecologies, tant to establish peer group dominance. At this age, the implication being that individuals might have youngsters experience rapid change in body size, different dominance status in different groups and along with changes in environment, as they move ecologies (deWaal, 1985; Hartup, 1983; Strayer, 1980). from primary to secondary school. The argument that Although explicable in terms of advantage to domi- males use R & T to establish dominance as they move nant individuals, dominance hierarchies also medi- into adolescence is also consistent with theory and ate group members' access to valued resources and research in the animal literature (Dunbar, 1988; Fa- reduce intragroup aggression in many situations gen, 1981). (Dunbar, 1988). Data from observations and interviews suggest We postulate that R & T may serve a social func- that R & T may be involved in dominance in two tion in peer groups, for boys especially, by assisting ways, each of which is age-related. The first is indi- in the establishing and maintaining of dominance re- rect; R & T may provide a way of assessing the lationships. The idea that R & T is related to estab- strength of others so as to decide one's strategy vis- lishing and maintaining dominance status is consis- a-vis dominance competition-a form of quot;ritualized tent with arguments from design. Males often use aggression,quot; as described in other mammalian spe- quasi-agonistic displays (e.g., soft or no-contact kicks cies, which leads to real fighting in only certain cir- and punches, light pushes) in the service of domi- nance. Very similar behaviors are also displayed in cumstances. Observations by Paquette (1994) support the idea that young chimpanzees can use R & T to R & T (Blurton Jones, 1972), but these behaviors are learn the strengths and weaknesses of others in plan- embedded in a nonserious context: Kicks and ning challenges for dominance, suggesting that punches do not make contact, and if they do they are R & T is more useful for this than real fights because soft; players are smiling; and they often handicap of the lesser chance of injury or intervention by a themselves (e.g., let the player on the bottom of a pile third party. get on top). Similarly, children's R & T occurs in symmetrical Because self-handicapping seems to occur in the groups, or with children of similar dominance status, R & T of both nonhuman primates and children, Sy- and many children say they can determine their own mons (1978) was critical of the hypothesis that R & T as well as peers' strength from these encounters is related to dominance. However, subsequent find- (Smith, Hunter, Carvalho, & Costabile, 1992). R & T ings counter this argument in two ways. First, chil- tends to occur between friends (Humphreys & Smith, dren can often evaluate the strength of others from 1987; Smith & Lewis, 1985) and in groups of three to R & T bouts, despite self-handicapping and restraint. four children (Pellegrini, 1993); these findings indi- Second, in some youngsters, especially by adoles- cate that it is a safe and relatively visible venue to cence, it now appears that subtle or not so subtle test and exhibit physical strength. Thus, through forms of quot;cheatingquot; may occur, demonstrating R & T, children can, in an indirect way, assess their clearly to opponents and to onlookers that one partic- own strength and that of others; in this way they pre- ipant is in fact stronger (Neill, 1976; Pellegrini, 1995b; pare for dominance encounters through the primary Smith & Boulton, 1990). In fewer cases, youngsters school period. initiating R & T turn it into aggression (Pellegrini, The second way in which R & T may provide the 1988, 1995b). A dominance function is also consistent with the context for establishing or maintaining dominance is more direct. Participants may use an R & T bout to gender differences in R & T. Children establish and get their partners in a position where they can actu- maintain dominance in different ways. Girls use pri- ally display their superior strength or assert domi- marily verbal rather than physical means to gain and nance, for example, by pinning or intimidating a keep resources (Charlesworth & Dzur, 1987). Boys, playmate. Participants doing this may have lulled on the other hand, use a variety of skills, some of
  13. 13. Child Development 588 (1995b) shed further light on this age trend. In a lon- their partners into a false sense of security by using the predominantly playful nature of R & T, or may gitudinal study of adolescent boys, he found that asymmetrical choices for R & T were observed dur- have used the self-handicapping and reversal criteria ing the first year of middle school (12 years), but not of R & T to get themselves into a quot;winningquot; position. This could be called a quot;cheatingquot; use of R & T for the second (13 years). He also found that during the first year of middle school, boys' R & T was corre- dominance purposes. For preadolescents, in contrast to adolescents, lated with peer-nominated dominance; only with so- R & T is not correlated with peer-nominated domi- ciometrically rejected boys, not popular or average boys, did R & T lead to and relate to aggression, how- nance, and it occurs with partners of similar domi- nance status (Humphreys & Smith, 1987; Pellegrini, ever. During the second year of middle school, R & T continued to relate to dominance status, but 1993); also, in most cases, R & T is not exploited for it did not lead or relate to aggression. These results immediate aggressive ends (Pellegrini, 1988). This suggest that R & T is used to establish dominance in suggests that R & T may not be used to establish dominance in this second direct way before adoles- early adolescence; once established, the hierarchy re- duces aggression, and R & T declines. cence. Rough-and-tumble play and actual fighting re- main separate for most children during the primary R & T and EmotionalCoding Skills school years; there are cases, however, involving so- An important dimension of social skill is the abil- ciometrically rejected children especially (Pellegrini, 1988), where R & T and fighting are linked. The eth- ity to encode and decode social signals. Successful nographic record also provides illustrations. Sluck- encoding and decoding of messages, such as quot;This is in's (1981) in-depth study of British 5- to 9-year-old play,quot; is necessary if play is to be initiated and main- children's behavior and perceptions of their lives in tained (Bateson, 1972; Bekoff, 1995). Behaviors that the school playground provides examples of R & T send the message quot;This is playquot; are typically exag- being used to deceive and manipulate peers. Simi- gerated, compared to more functional counterparts (Biben & Suomi, 1993); for example, play fighting, larly, the work of Oswald and colleagues (Oswald, Krappmann, Chowduri, & Salisch, 1987) in Germany compared to real fighting, might be characterized by an open mouth, hunched shoulders, and rhythmic with children aged 6 to 10 years found instances of hurtfulness in the play of the older children in this movement of the hands. Research by Parke and colleagues indicates that age range. However, a different picture emerges in early ado- the ability to encode and decode play signals can originate in vigorous play between parents (primar- lescence. Neill (1976, p. 219) was the first to suggest that adolescent boys' R & T might be used to estab- ily fathers) and their children (primarily sons) begin- ning in infancy and continuing throughout child- lish dominance. His factor-analytic study of 12- to 13- year-old boys' playground behavior found that hood (Carson et al., 1993; Parke, Cassidy, Burks, R & T and aggression often co-occurred. Neill stated Carson, & Boyum, 1992). They found the amount of time spent in vigorous play bouts to be positively re- that R & T might be a quot;means of asserting or main- taining dominance; once a weaker boy has registered lated to preschool children's ability to decode emo- distress the bond can be maintained by the fight tak- tional expressions, such as happy, sad, angry, scared, ing a more playful form, but if he does not do so at and neutral (Parke et al., 1992). Further, children's ex- pression of emotional states was also related posi- the start of the fight, the stronger boy may increase the intensity of the fight until he does.quot; tively to bout length (Parke et al., 1992). Involvement in R & T with peers, expressed in terms of proportion This age change in the function of R & T received some support from Humphreys and Smith (1987). of total behavioral output, has also been found to re- They found that at 11 years, but not at 7 and 9 years, late to primary school children's ability to decode dominance was a factor in partner choice in R & T. play signals (Pellegrini, 1988). It may thus be the case that parent-child play provides the groundwork for When the younger children engaged in R & T, they children's ability to encode and decode emotions, did so in symmetrical groups, or with peers of similar dominance status; for the older children, dominant with this ability later being used in physical activity play with peers. youngsters initiated R & T with less dominant However, there are difficulties with this hypothe- youngsters, or in asymmetrical groups. sis. First, these correlational studies do not establish This finding would be consistent with stronger cause and effect; it is equally plausible that the causal children using R & T to exhibit dominance with relation is such that those children less able to weaker children. Results from a study by Pellegrini
  14. 14. and Smith 589 Pellegrini tions of strength training, endurance training, and encode/decode emotions are less willing to engage skill and economy of movement. in R & T. Second, and more conclusively, these Related to this, we need more data on gender dif- hypotheses are inconsistent with observed gender ferences in exercise play, unconfounded by R & T. differences; encoding and decoding of emotions We can be confident of the gender differences in should be just as important for girls as for boys, and R & T, and they fit readily with the predominant they certainly are no worse at it than boys. Yet the functional hypothesis for R & T-social dominance. gender difference in R & T is a well established Gender differences in exercise play are more intri- finding. guing with respect to functional hypotheses. Con- In summary, we hypothesize that the primary ceivably, these differences may be more complex and function of R & T through the primary years is to pro- differentiated than previously thought, as Silverman vide a way in which boys assess the strength of others and Eals (1992) found in the domain of spatial ability; for dominance purposes; it may also provide practice for example, gender differences might be different for in fighting skills, but little direct evidence exists to aspects of exercise play relevant to strength as op- support this. There is good evidence that in early ad- posed to those relevant to endurance. olescence (and perhaps earlier for rejected children) R & T can function to actually establish dominance status in boys' peer groups. The contemporaneous Functions of Exercise Play for Strength, Endurance, correlations between R & T and dominance and and Economy and Skill of Movement R & T and popularity for adolescent boys suggest The benefits of exercise play for two dimensions that R & T is only one behavioral strategy used by of motor training-strength and endurance-should boys to gain and maintain status. Finally, we hypoth- be immediate and occur across the life span. By im- esize that any benefits for emotional encoding or de- mediate we mean that strength and endurance will coding are incidental benefits of R & T, achievable in result from repeated activity bouts, usually across the other ways, rather than functions. span of a number of weeks (Byers & Walker, 1995). However, we need more information on duration, frequency, and intensity of physical exercise of both SUGGESTIONS FOR FUTURE RESEARCH the playful and nonplayful variety from infancy In light of the relative paucity of research in the area through adulthood, and the correspondence between of physical activity play, we suggest directions for these data and measures of immediate and sustained future research on the nature of such play and its hy- fitness. To test the hypothesis that exercise play re- pothesized benefits in physical, cognitive, and social lates to bone remodeling and physical endurance and domains. strength, as measured by decreased heart rate during exercise or VO2Max (the maximum rate of oxygen uptake during exercise), we need to measure the sep- The Need for Naturalistic Data on Forms and arate contributions of nonplayful and playful vigor- Amounts of Physical Activity Play ous activity to physiological measures of endurance There is a need for more descriptive data on the and strength. forms of physical activity play and their age trends through childhood and adolescence. The review by Function of Exercise Play for Cognitive Byers and Walker (1995) and our own analyses here Performance show the importance of age trends in examining The beneficial consequences of exercise play for functional hypotheses. Yet, for exercise play espe- cially, data are scanty. Although we can be reason- children's cognitive functioning are not firmly estab- ably confident of the inverted-U curve with age, we lished. Although exercise play breaks are related to cannot be confident that the peak is at 4-5 years as children's attention to classroom tasks (Pellegrini & we have assumed. Also, different types of exercise Davis, 1993; Pellegrini et al., 1995), alternative expla- nations abound. Future research should examine the play may peak at different ages, and the develop- mental course may be different for boys and girls. extent to which cognitive performance-for example, task attention measured by gaze and heart-rate vari- The difference in age peaks between exercise play and R & T, together with other differences, has led us ability and possibly vagal tone (Obrist, Howard, Sut- terer, Hennis, & Murrell, 1973; Porges, 1992) for chil- to separate them for functional consideration. Simi- larly, different aspects of exercise play and R & T dren of different ages-is increased as a function of may relate to somewhat different, if related, func- quot;breaksquot; during cognitive tasks.