ANT2416 EXAM TWO Human brain growth 370g infant 1350 g adult o Chimpanzee brain growth 175g 350g o Brain mass approaches mature size before body mass reaches mature o Human infants and children direct enormous amounts of energy toward brain growth development Neuron distinctive in it s ability to communicate with other neurons o 100 billion neurons at birth Neurons communicate with one another via synapses o Developing networks of synapses mature structure function of size the brain Synaptogenesis creating new synapses new connections between neurons o The rate of synaptogenesis in each brain system varies with age o Visual and auditory cortex reach mature level of synaptogenesis early less than 5 years o The frontal lobes involved in higher cognitive processes are the last to attain adult levels of synaptic connectivity Human brain growth 370g 1350g o Increase in size growth of dendrites axons synapses after birth 1000 trillion synaptic connections o Add glial cells one trillion glial cells o Add myelination of axons billions of neurons Myelin fatty sheath around the axon increases the rate of conduction o Before Birth Create neurons neurogenesis complete by 7 months gestation Move neurons into position migration Aggregation into layers Create neural circuits synaptogenesis o After Birth Grow more axons dendrites create many more connections continue synaptogenesis Myelination to increase speed of conduction Pruning of some synapses Maturation of frequently used synapses use it or lose it Harry Chugani pediatric neurologist o Glucose metabolism shows active areas of synaptogenesis o Using PET scans to measure glucose metabolism PET positron emission tomography a nuclear medical imaging technique Newborn brainstem thalamus reflexive 3 months cerebellum visual auditory tactile cortex sensory and motor development 6 8 months frontal occipital lobes 24 months brain as active as adult 36 months brain is 2x as active as adult 3 10 years remains twice as active 10 18 years gradual drop to adult levels Brain building is especially active in childhood 3 10 years old Birth 2 500 synapses per neuron 3 years 15 000 synapses per neuron Adult 5 000 synapses per neuron The adult brain is a highly specialized device that responds specifically to specific kinds of stimulation Particular parts of the brain even individual cells are designed to respond to information from the outside world in particular ways Where does this specialized structure come from Some structure is clearly built in but the brain also seems to change radically in response to experience Experience changes the brain but then those very changes alter the way new experience affects the brain Gopnik Rate of play behavior also varies with age o In Norway rats domestic cats and house mice the ages at which play rates reach a peak match the ages of terminal synapse formation and elimination in the cerebellum o These analyses suggest that the true function of play is to modify brain development o If the benefit of play primarily involves brain development then play should vary with relative brain size Byers The distribution of play behavior among Australian marsupials o Three categories of play rate Play absent Play rudimentary Play common o When controlled for body mass brain mass was significantly associated with level of play o A larger adult brain requires a relatively longer period of postnatal brain development o A longer period of postnatal brain development implies a longer period during which experience is able to modify brain development Animals with brains that do not change much after birth do not play o Animals with brains that are shaped by experiences after birth rely on play to help finalize the brain s adult architecture Responsibility in Childhood Three developmental trajectories Ochs A consistent and central aspect of any culture is subsistence food acquisition o Foraging food collection of what the environment produces hunters and gatherers o Horticulture plant food production in which everyone must participate because yields are low o Pastoral animal food production in which everyone must participate o Agriculture water management fertilizer and harnessing animal or mechanical energy allows few people to feed many people provides the basis for larger social groups towns cities nation states o Industrial very high levels of efficiency in food production and distribution allow mega societies such as the USA 300 million people to be part of a single political group Subsistence affects the size and character of the social group o Small scale societies band tribe Foraging Horticulture Pastoralism o Large scale societies State Matsigenka Agriculture Industrial 1995 35 communities o Horticulture foraging hunting gathering o Egalitarian relations o From birth a network of family community in constant contact o From early childhood specific training in paying attention to others o Trial and error autonomy for task learning error correction o Task assignment by others work is an ought o Both family community member encourage child compliance o Stories as an additional source of support for the value of work Samoan 1978 o Horticulture and fishing o Hierarchy o From birth infants are embedded in a network of family community constant contact o Community work distributed responsibility o Hierarchy within extended family o Young children are prompted to notice accommodate others o Young children participate in work o Support is expected and acknowledged Los Angeles 2001 2004 middle class dual income o Large scale industrial efficiency of food production o Extreme time sensitivity minutes count o Child centric but only for a portion of the day o Interventions by parents o Giving credit to children without acknowledging parental help o Battle for power o Idealization of autonomy vs actuality of dependence Emotional Development Emotion o Experiential component o Expressive component o Motivational component o Physiological component Charles Darwin 1872 The Expression of the Emotions in Man Animals o Studied emotional expression in children o Wrote letters to people around the world asking about similar facial expression under similar circumstances o No other mammal emphasizes facial communication as much as primates do Carroll Izard s study of facial expression of emotion in very young humans joy anger sadness disgust distress pain interest fear surprise o Smiling is an engaging expression which delights caretakers Konner