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Lecture 8

Lecture 8 – end of Genetics, Epigenesis, and Plasticity, beginning of Cognitive Development - The Piagetian approach

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March 14, 2011 Genetics, epigenesis, and plasticity con’t Essay  Zero in on a specific chapter in the textbook, read it, then do independent work to find relevant journal articles – good idea to read stuff by the people cited in the textbook  Use at least 10 journal articles, MUST be peer-reviewed, ideally within the last 10-15 years  Books are okay only within the last 5-10 years, and if their authors have written in peer-reviewed journals  Older your sources, more likely they’re irrelevant now  APA format – only include the things you actually cited, not things you just read o In-line citations Genetics, epigenesis, and plasticity  Becoming increasingly more difficult to separate nature and nurture, which is why this debate is dissolving  What would lead us to think that environment is not independent from genes but that genes are independent from environment?  What’s Lamarkian evolution? o The idea that animals can pass on acquired characteristics o Fairytale version of Lamark – why giraffe’s have long necks – they stretched lots to get to tall trees, did lots of giraffe yoga, and their necks got a little longer, and they passed that on to their kids, etc etc o Before Darwin, this was a plausible solution  But now we know better – people synthesized Darwinian evolution with Mandelian genetics - there’s nothing we can do to pass on acquired characteristics to your offspring – if you lose a leg in an accident, you’re not going to pass on the loss of a leg to your child  This seems to imply that genes can’t be affected by the environment – only across generations (mutations, genetic drift)  How to make a distinction between gene structure and gene activity - yes, the genes themselves cannot be affected by the environment, but how they are turned on and off can  This is a large part of epigenesis  Neuroplasticity = significant influence of environment on gene expression Genes --> gene activity enzyme protein -> muscles/neurons  How is there feedback between gene activity and enzyme protein? Enough protein will turn off gene – two-way causation  Hugely affected by biological factors  Feeds back to other levels – feedback loops within feedback loops within feedback loops – self-organizing system  Each level can be described as either nature or nurture – not clear which can be described as which as any given time  “the environment” isn’t a single thing – a room, a building, a country, etc – even your body can be considered an environment – nature and nurture are no longer independent or singular – there isn’t a single part of the diagram we can point to and say “THIS is the environment” or “THIS is nature”  genes shape environment, environment shapes all gene activity and above  this means we have a new account of what development means o development used to be learning, maturation, additive interaction between the two o the above is neither learning, or maturation, or simply a combination of the two – development is EMERGENCE – Bjorklund’s theory, example of little girl learning to play violin from earlier lecture  dynamical systems are simultaneously integrating into wholes and differentiating into parts  complex systems produce emergent functions, new abilities – this is what it means to be a complex system – more different kinds of interaction with the environment while maintaining your integrity as an organism/system  brain = epigenesis on speed, in a way – tremendous plasticity  two types of plasticity – synaptogenesis and neurogenesis o synaptogenesis – ability to grow new synaptic connections or kill existing ones o neurogenesis – ability to grow new neurons or kill existing ones  this process is directly affected by environmental factors  certain behaviours can lead to cortical thickness – if you are a violin player, the part of your brain associated with fine fingers movements will be bigger and stronger  long term meditators have increased introspective awareness - “you can train your mind to change your brain”  your brain is a machine of machines that can make itself into a new kind of machine – way more advanced than a computer  computers are only capable of quantitative development – not qualitative  emergence through dynamical systems is one of the most powerful explanations as to why development occurs in a stepwise pattern  dynamical system that occurs between nature and nature has much more to do with development then genes or environment on their own  emergent dynamical system shapes development in powerful ways  MAOA – enzyme that is a catalytic reaction for several neurotransmitters in the brain – MAOA levels are correlated with increased aggression and anti-social behaviour o People who have done research on this: o Caspi et al 2002 o Bjorklund o Mark Lewis  Correlations between MAOA levels, child maltreatment and antisocial behaviour as well – study aimed to look at all three factors  Maltreated boys predictive of antisocial behaviour, especially for children that had low MAOA  Lower MAOA on its own was not correlated with highly anti-social behaviour  Only low MAOA and maltreatment as a child greatly predicted antisocial behaviour  Maltreatment as a child generally predicted anti-social and aggressive behaviour o Epigenetics – species of interactionism  Brain is constantly redefining itself as a dynamical fashion  Highly accelerated in the brain  Push itself to qualitative change  Bronfenbrenner and Ceci’s bioecological model o Very good at accommodating the facts of epigenesis and plasticity o Layered environment – environment does not refer to a single thing o Proximal process – genes can only exert this influences when certain experiences activate them – interactions between the child and its direct contact environment o Proximal processes must occur regularly and for an extended period of time o Degree to which environment supports proximal processes and the regularity and duration of these process has a large impact on gene expression and activity, hence it is a bioecological model o Ex. Take North-American child and put them in a war-torn environment  High stress environment – high cortisol  Cortisol destroys your hippocampus, destroys working memory and ability to learn – if you can’t learn and remember, you find your environment more stressful, which produces more cortisol, further killing your hippocampus, making you more sensitive, so you find the environment more stressful, more cortisol, etc. you become the stressful environment – you are hugely responsible for your development o Clearer model of gene-environmental relationship – core issues of developmental psychology Cognitive Development o Piaget is talking about development of logical competence, scientific reasoning o Four main periods of development o Sensorimotor – age 0-2 o Pre-operational - age 2-6 o Concrete operational - age 6-12 o Formal operational - age 12-adult  Does everyone make it to this stage? Is this where everyone stops? Is there any opportunity for post- formal development? o Sensorimotor stage has six sub-stages  1. Birth to one month of age – exercising reflexes  child starts with simple, biologically provided reflexes o rooting reflex – if you stroke its cheek, it will turn and suck your finger  tried to assimilate as much as possible  assimilation eventually leads to accommodation  but, Piaget underestimated the sophistication of children’s inborn learning mechanism – overly simplistic model  basic structural abilities go from being reflexes to sensory-motor schemes  2. 1-4 months of age – developing schemes  sensory-motor schemes - skilled and generalizable action patterns that the infant uses to manipulate and make sense of the world  individual schemes become much more specialized – complexification is occurring – schemes are integrated together into higher order schemes  particularly important form of this integration is intermodal or intersensory integration – different senses agree on what’s going on in the environment.
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