Hockenbury Discovering Psychology 5th txtbk

Development During Infancy and Childhood377Age (months)0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 21 22Rolling overGrasping rattleSitting without supportStanding while holding on25% of babiesacquire this skillat this time......50% bythis time......and 90%by this time.Standing alone wellWalking wellFigure 9.3 Milestones in Infant Motor DevelopmentEach bar in the graph shows the typical range of agesfor acquiring a particular motor skill during infancy.Given the wide range of individual variation, can yousee how simple statistical averages may be misleading?Building tower of two cubesWalking up stepsbrain. At birth, her brain is an impressive 25 percent of its adult weight. In contrast,her birth weight is only about 5 percent of her eventual adult weight. Duringinfancy, her brain will grow to about 75 percent of its adult weight, while her bodyweight will reach only about 20 percent of her adult weight.One outward reflection of the infant’s developing brain is the attainment of moresophisticated motor skills. Figure 9.3 illustrates the sequence and average ages ofmotor skill development during infancy. The basic sequence of motor skill developmentis universal, but the average ages can be a little deceptive. Infants vary a greatdeal in the ages at which they master each skill. Although virtually all infants arewalking well by 15 months of age, some infants will walk as early as 10 months.Each infant has his own inborn timetable of physical maturation and developmentalreadiness to master different motor skills.temperamentInborn predispositions to consistentlybehave and react in a certain way.Social and Personality DevelopmentFrom birth, forming close social and emotional relationships with caregivers isessential to the infant’s physical and psychological well-being. Although physicallyhelpless, the young infant does not play a passive role in forming these relationships.As you’ll see in this section, the infant’s individual traits play an important role inthe development of the relationship between infant and caregiver.Temperamental Qualities: Babies Are Different!Infants come into the world with very distinct and consistent behavioral styles.Some babies are consistently calm and easy to soothe. Other babies are fussy, irritable,and hard to comfort. Some babies are active and outgoing; others seem shy andwary of new experiences. Psychologists refer to these inborn predispositions to consistentlybehave and react in a certain way as an infant’s temperament.A temperamental bias can be likenedto the basic form of the song of aparticular species of bird. The animal’sgenome constrains the basicarchitecture of the song but does notdetermine all of its features; withinbroad limits, the adult song dependson exposure to the songs of otherbirds and the opportunity to hear itsown vocalizations. A similar principleholds true for the effect ofenvironmental influences on people.JEROME KAGAN (2004)