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cognitive development chapter 1 notes
biological bases of cognitive development
evolution and cognitive development
● evolutionary development is rooted in darwinian theories ○ natural selection: some members survive and reproduce → inherited traits pass on ○ reproductive fitness: the likelihood that an individual will become a parent and a grandparent
evolutionary developmental psychology
● cognitive psychology is the “missing link” in explaining the evolution of human behavior ● cosmides and tooby proposed that information-processing mechanisms + environment = behavior ● adaptations : alterations in the structure/function of an organism that provided a survival or reproductive benefit ○ physical changes: better fine-motor coordination, bigger brain, etc. ○ behavioral, emotional, and cognitive functions also adapt/develop ○ deferred adaptations : adaptations that prepare infants for current and later environments ■ maintaining social relations (w/ primary caretaker and later peers) ○ ontogenetic adaptations : adaptations that benefit the infant only during a specific time in development, then disappear when no longer needed ■ umbilical cord (keeps infant alive in utero, useless after birth) ■ neonatal imitation (newborns sometimes match facial expressions of an adult model) ■ has been observed in those with Down syndrome &/or later autism ■ could be seen as a result of social interactions with mothers and can predict positive social behaviors in infants ● constraints on learning ○ infants are born with sets of perceptual/cognitive skills related to info-processing across domains: ■ understanding the physical world (objects cannot go through each other), numbers (1+1=2), biological world, social world ○ humans are “prepared” by natural selection to process some information better than others
■ but…these constraints come from structured gene-development-environment interactions
evolved probabilistic cognitive mechanisms
● prepared fear: children do not have innate fears, but learn from others’ responses
structure of the mind
● david geary’s structure of the mind is a hierarchy with domain-specific modules ○ two overarching domains: social (folk psychology) & ecological ■ each has domain-general resources then domain-specific ■ social: self, individual, group ■ ecological: biological, physical ● cognitive mechanisms and abilities begin broad then become more specific as a result of experience ○ humans have time to gather the necessary experience to function optimally into adulthood ● humans spend more time as juveniles than any other primate → must be some survival benefits ○ could be due to need for children to master human culture before adulthood ■ because of the social and physical environments people live in, they need more time and flexibility to adapt to diverse environments
biologically primary vs. secondary abilities
● primary: cognitive abilities selected over the course of evolution (i.e. language) ○ acquired universally ○ undergone selection pressure & evolved to deal w problems faced by ancestors ○ acquired by children in all but the most deprived of environments ○ children typically have high motivation to perform tasks involving these ○ most children attain “expert” level of proficiency ● secondary: skills built on primary abilities but are primarily cultural inventions (i.e. reading) ○ no evolutionary history ○ culturally determined, reflect the cognitive skills important in a particular culture ○ need tedious repetition and external pressure to be mastered ● evolutionary developmental psychology is rooted in plasticity : the ability to change as a result of experience ○ children are sensitive to early environments & adjust brains, cognitions, and behaviors accordingly
gene-environment interaction
■ adolescents and adults can learn a second language but with great difficulty ● example: auditory and visual stimulation of bobwhite quail → the slower development of vision allows the auditory system more time to develop without competition ○ when given premature visual stimulation, they went to the chicken or no preference over preferring the bobwhite ○ the timing of perceptual experience is critically important ■ early experience is not always better experience ● minimal research done on human infants for sensory overstimulation but researchers think some deficits in premies could be exposure to too much sensory information too soon
genotype → environment theory
● one’s genotype influences which environments one encounters and the type of experiences one has ● genes drive experience ● genotype of parents dictates genotype of child & rearing environment → genotype of child dictates phenotype and rearing environment → phenotype and rearing environment influence each other
3 types of genotype → environment effects
● passive: when genetically related parents provide the rearing environment of the child ○ when biological parents rear a child, we cannot separate the effect of genetics and environment ○ decline with age ● evocative: when child elicits responses from others that are influenced by their genotype ○ attentive/cooperative children receive more positive interactions than distractable/uncooperative children ○ remain constant with age ● active: when children seek out environments consistent with their genotypes ○ children interested in sports would seek out like-minded children to play with ○ increase with age
genotype → environment & cognitive development
● parents’ environmental influence on children should be greatest during early childhood and decrease with age ○ as children grow, active genotype → environment effects increase ○ adoption study: adopted siblings in early childhood have moderately similar IQs, but a correlation of 0 when older ■ siblings become less alike the older they get → can select environments that suit their needs
● since genotype causes children to choose certain environments, they can “craft” their intelligence
development of the brain
● unlike other species, the human brain has self-awareness and behavioral flexibility ○ major differences between human brains and other mammals are in the greater amount of area that is devoted to the cerebral cortex & extended period of postnatal growth ● at birth, human brain weighs 360 grams (~28% of its eventual adult weight) ○ the brain accounts for 10% of overall body weight of a newborn but only 2% of the overall body weight of an adult ○ by 6 months, brain weighs 50% of what it will in adulthood; 75% at 2 years; 90% at 5 years; 95% at 10 years ○ brain grows rapidly before birth and continues postnatally ● the infant brain is underdeveloped ○ directs basic physiological functions (breathing, wake/sleep cycles), but cannot control coordinated movement or human-specific mental operations ● average weight of a newborn chimpanzee’s brain is 135 grams → ~47% of eventual adult weight ○ why? obstetrical dilemma (extrauterine spring, the fourth trimester) : human infants are born before brain is that developed because otherwise their skulls couldn’t fit through birth canals ○ therefore, infant brains develop rapidly while exposed to more physical and social stimulation that typical primate brains would be more mature to experience ■ substantial influence on brain, cognitive, and social development
neocortex/cerebral cortex
● part of the brain most associated with thought ● most recent structure to appear in evolutionary time → associated with mammals, greatest manifestation in primates & especially humans ● neocortex, specifically frontal/prefrontal lobes, provide characteristics we most associate with humanness ● neuroimaging techniques: ○ high-density event-related potentials ■ form of EEG that allow for detailed recording of brain activity when people solve cognitive tasks ○ positron-emission tomography (PET) scans; single-photon emission computed tomography (SPECT) ■ radioactive materials are injected into participants, changes in radioactivity are used to reflect glucose consumption in those areas of the brain
○ but in general, new neurons are typically not produced after birth
migration : once produced, cells migrate to their permanent position in the brain
● not all cells migrate at the same time, but most cells arrive to final position by 7 months after conception ● it is important that cells destined for a certain part of the brain end up where they are meant to be ○ fault neural migration is associated with disorders like cerebral palsy, epilepsy, intellectual impairment, and learning disorders
differentiation : once at their final destination, neurons grow in size, produce more/longer dendrites, and extend their axons away from cell body
● synapses are created when an axon meets an appropriate dendrite from another neuron
synaptogenesis and selective cell death
synaptogenesis : the process of synapse formation
● rapid during the early years of life when the brain is first becoming organized ● continues throughout life as the brain changes in response to new information ○ rate is never as fast as it is in prenatal and early postnatal months
apoptosis : selective cell death
● synaptic pruning and cell death occur as infants have more synapses and neurons than needed ● occur at different rates for different parts of the brain ● children with high IQs had thinner cortices; children with exceptionally high IQs showed an early acceleration of cortical growth followed by an accelerated thinning in early adolescence
rises and declines in neural development
● aspects of brain development show a rise and decline over childhood ○ basic metabolism of the brain increases after first year of life and peaks at 150% of the adult rate from ages 4- ● developmental changes occur in the presence of various neurotransmitters → several show increases followed by decreases over infancy and childhood ● function of rise and fall: ○ hypermetabolism in preschool years may be necessary for the rapid learning at the time
how do young brains work?
● some say genetics, other say experience plays a big role as well ● there is a reciprocal relationship between brain and behavioral development ○ nervous system has been prepared by natural selection to expect certain types of stimulation ○ although the infant is “prewired” for certain experiences and to develop certain abilities, abilities are influenced by experience ● experience-expectant processes: ○ rats and cats reared in darkness struggle with visual discrimination ■ same w/ cataract patients who gain sight via surgery ● behavioral effects of sensory deprivation are reflected in changes at the neuronal level ○ when a kitten’s eyes first open, ~1/2 of the neurons in the visual cortex respond → after a few weeks of seeing, all the cells are used ■ but without any patterns of light (i.e. no objects), cells of the visual cortex make less connections with others cells, lose their sensitivity to orientation ■ experience changes the structure and organization of the young brain ○ infants with cataracts removed had a typical pattern of visual development → but the longer the delay before removal, the poorer vision was ■ even for infants with cataracts removed early and normal vision developed, some aspects of face processing impaired ■ different sensitive periods for different brain areas? ● experience-dependent synaptogenesis : second process of synapse development that reflect the unique experiences of an individual rather than universal experiences ○ when experiences are not had, those neurons die
development of the neocortex
neocortex/cerebral cortex: multilayered sheet of neurons that surrounds the rest of the brain
● includes: ○ frontal lobe ○ association region (thought and consciousness) ○ motor region (bodily movement and coordination) ○ premotor region ○ association region (auditory cortex) ○ central fissure ○ sensory region (bodily sensation) ○ parietal lobe ○ occipital lobe ○ association region (visual cortex) ○ sensory region (sight) ○ temporal lobe ○ sensory region (hearing)
the brain’s plasticity
plasticity : the brain’s ability to change → potential outcomes that are possible for a single neuron, a bundle of neurons, or a larger brain structure
neuronal plasticity
● little to no plasticity in neurogenesis in the cerebral cortex ● new synapses are formed from experience ○ lab animals raised in different environments → enriched environments included interactions → these rats and mice are superior at many complex tasks ○ enriched animals have heavier/thicker neocortices, larger neurons with more dendrites, and more synaptic connections
synaptic plasticity
● greatest in infancy ● as we age and experience new things, neurons and synapses formed prenatally or postnatally die → connections that could have formed between those are now impossible ● experience serves to create new connections and also make other ones impossible/less likely ● we retain neural plasticity throughout life → change is the degree to which experience can change the brain & intensity of experience needed ● gene expression associated with synapse formation is similar in adult human brains to that of juvenile chimpanzee brains ● humans possess a form of neuronal neoteny ○ neoteny: the retention of infantile or juvenile features into later development ○ human neurons in particular association areas retain juvenile characteristics throughout adulthood → allows human brain to function somewhat like a juvenile brain throughout life ■ contributes to increasing information storage and processing capacity throughout life ● as we age, neurons become dedicated to certain functions → we don’t need plasticity ○ but retaining some is important because we experience new social situations over time
recovery of function from brain damage
● we can learn about plasticity of the nervous system from those recovering from brain damage ○ some studies documenting greater recovery of function when brain damage occurs earlier in life, other studies show the opposite ■ early plasticity & early vulnerability
● early plasticity : the brains of infants and young children are highly plastic relative to the brains of older children and adults → better able to overcome the adverse effects of brain damage ○ children with brain damage to language areas of left hemispheres before able to speak are eventually able to attain more advanced levels of language than older children or adults with similar brain damage ○ left-hemisphere brain injury for kids who can already talk creates an initial loss of language but language is recovered and kids talk at (near-)normal levels ■ adults don’t have the same recovery ■ even in young kids, full recovery of language is rare → the human brain is not completely plastic ○ kennard effect : if one must have brain damage, have it early, because a young brain is more likely than an older brain to recover normal function ■ however…this does not hold for all types of brain injuries ■ some produce more long-lasting negative consequences when experienced earlier in life → early vulnerability ● early vulnerability : because the brains of infants and young children are becoming increasingly specialized with experience, early damage can alter the typical course of development resulting in serious disruptions of normal neural organization and functioning ○ exposure to a teratogen (agents that can adversely affect the development of a fetus) interferes with formation of limbs early in prenatal life, before arms and legs have been developed → has no influence when exposed later in life, after limbs form ○ brain damage that occurs prenatally or early postnatally typical results in permanent neurological impairment ● recovery depends on a wider series of variables ○ when focus of damage is to an area with more general cognitive functioning (attention, executive function, intelligence measured by IQ not a specific ability) → recovery is often greater the later the damage occurs ○ young children and animals show more permanent deficits than older children and animals after brain damage to the frontal lobes ○ brain damage before 1 year resulted in lower IQs for children than similar brain damage after 1 year ○ greater reduction in IQ for children with brain damage before 5 than for after 5 ● plasticity (good recovery) ↔ vulnerability (poor recovery) ○ factors influencing recovery/outcome: ■ injury factors, age factors, environmental factors, interventions/rehabilitation
slow growth and plasticity
● when the course of a young child’s life changes drastically, patterns of development can also be radically altered
○ understanding the neurological mechanisms that underlie behavioral observations ● understanding both the neural and evolutionary causes of behavior and development will help psychologists ask better research questions and have a better understanding of development
