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Lecture 1+2 Development.docx

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McMaster University
Joe Kim

Lectures 1/2: Development Introduction To Development  Development refers to the changes and continuities that occur within the individual between conception and death  Developmental psychologists are interested in understanding how you change over time and also how you stay the same  Maturation o The biologically-timed unfolding of changes within the individual according to that individual’s genetic plan  How that plan unfolds is influenced by specific environmental conditions  Learning o The acquisition of neuronal representations of new information o Relatively permanent changes in our thoughts, behaviours and feelings as a result of our experiences o Through learning processes, we avoid touching a hot stove and look both ways before crossing the road o Learned processes can be controlled, but can also become so practised as to become automatic o Ex. As a child learning to cross the road, we learned to first look left and then right and cross when all is clear o As an adult, we do so automatically o However, this “left then right” strategy is not always the optimal behaviour o Many North American tourists are a little thrown off when they cross the road for the first time in a country where cars drive on the opposite side of the road o In this case, you have to overcome your past learning to use the optimal strategy to first look right and then left before crossing the road  Interactionist Perspective o Emphasizes that most of your developmental changes reflect the interaction of maturation and learning o Maturation affects learning  Some essential systems must be in place before learning proceeds  Ex. You won’t learn to walk until you’ve developed muscles in your torso and limbs and the ability to balance o Learning affects maturation  Ex. Imagine a child who was given proper nutrition, but isolated in a dark room, never being allowed to play or interact with anyone  You would expect problems in developing normal vision, speech, motor and social skills compared to any other child exposed to normal environmental stimulation  Without some minimal level of input to learn from the outside world, maturation will be absent or delayed Studying Development  Changes that occur earlier in life are much more dramatic than those occurring later in life  Many researchers believe that the developmental changes that take place during these early years play an especially important role in shaping who you become  Four ways to measure abilities in infants o Habituation procedure  To determine if an infant can detect the difference between two stimuli  Infants normally tend to show interest in novel objects in the environment  The habituation process begins by repeatedly presenting the infant with the same stimulus, such as a tone or a picture, while measuring changes in physiological responses, like heart rate and breathing or behavioural orienting responses like head and eye movements  When a novel stimulus is presented, an infant will initially show a burst of activity  As the same stimulus is repeatedly presented, the infant’s responses will return to baseline levels  At this point, the infant has demonstrated habituation to the stimulus  At some level, the infant still recognizes the stimulus as the same, it is just no longer important  The stimulus can be changed and if the infant recognizes the change by distinguishing the new stimulus from the old one, she is said to dishabituate and shows another burst in physiological response  Habituation  A decrease in responsiveness to a stimulus following its repeated presentation  Dishabituation  An increase in responsiveness to a stimulus that is somehow different from the habituated stimulus o Event-related potentials  An measure of the brain electrical activity evoked by the presentation of stimuli  To measure ERP, a special cap with an array of electrodes is carefully placed on the scalp  These electrodes can detect changes in electric activity across a population of neurons in the brain  The particular behaviour being measured will evoke changes in various brain regions of interest  If you were presenting the infant with a visual stimulus, you may expect changes in activity in the occipital lobe of the brain, an area devoted to visual processing  If you were presenting an auditory stimulus, you may expect changes in activity in the temporal lobe region, an area devoted to auditory processes o Together, habituation and ERP provide complementary behavioural and neural measures to understand an infant’s sensory interactions with the environment o High-amplitude sucking method  How do you ask an infant what she likes or dislikes  One method takes advantage of the fact that infants can control their sucking behaviour to some extent, which can be accurately measured by a special pacifier in HAS method  You first measure the baseline sucking rate for the infant in the absence of relevant stimuli  During the shaping procedure, the infant is given control over the presentation of a stimulus to be tested, such as a series of musical notes  If the infant sucks on the pacifier at a faster rate than the baseline, a switch is activated in the pacifier that causes the stimulus to be presented  If the infant can detect the musical notes and likes what she hears, she can keep the musical notes playing for longer by increasing her sucking rate  If the infant doesn’t like the sounds, she can stop sucking sooner to end the presentation o Preference method  Infant is put in a looking chamber to simultaneously look at two different stimuli  The researcher can accurately measure the direction that the infant is looking to tell if more attention is being directed to one stimulus over the other  Researchers have found that infants tend to prefer looking at big patterns with lots of black and white contrasts and prefer looking at faces  Inferences and Assumptions of Procedures o Suppose you were measuring evoked fear by measuring the escape time of a person presented with a stimulus of a ghost in a haunted house o If the subject had a broken leg, it would obviously be a mistake to infer a lack of fear from a slow escape time o Such a test would lack validity of the intended measure  Competence-Performance Distinction o Researchers testing infants and children must be particularly aware of the competence-performance distinction o If a child fails to perform a certain task, this may reflect a genuine lacking in competence in the cognitive ability of interest o However, a child may have indeed developed the cognitive ability of interest, yet still be unable to perform the task o Ex. A child who is preverbal will be unable to respond to your questions on her preferences between two different toys  If you were unaware that she was preverbal, you may wrongly assume that failure to respond to your questions indicates that she is unable to discriminate between the two toys  Given a better test, the child may be able to demonstrate her preference to you Introduction to Developmental Research Designs  Longitudinal design o Researchers examine the abilities and characteristics of the same individuals repeatedly over a subset of their lifespan o If you were interested in how memory for lists of numbers changes with age, you might test the same group of people every year on the same type of test from 5- 75 years old o Can uncover age differences and find patterns that are common to all people o Allows researchers to assess developmental change o Drawbacks  Very expensive and time consuming  Problem of selective attrition  Some participants may quit, become unfit to continue or even die  Leaves a fundamentally different sample at different time points  Problem of practice effect  Subjects may improve performance based on prior exposure alone rather than on natural development over time of skills being studied due to same or similar tests being administered over years  Cross-sectional design o Many different individuals from different age groups are tested at once without the need to be tracked over the span of many years o Allows researchers to assess developmental change o Relatively less time consuming and expensive o Can uncover age differences o Drawbacks  Can’t be sure if differences between age groups are due to developmental changes or due to generational effects  If 25 year olds perform better than 50 year olds, perhaps the generation of 50 year olds have had less early training with numbers compared to the generation of 25 year olds  Are not directly tracking changes with age  Each person is only studied at a single timepoint, you are not really observing what happens as a person ages  Instead, are making inferences on trends in group data  Final alternative is to combine both designs o Combines the strongest and weakest features of both design types in one Introduction to Hereditary Transmission  When a sperm penetrates an ovum, a new cell is formed, called a zygote  This single cell contains 46 chromosomes, 23 chromosomes from each parent  A chromosome is a threadlike structure that is made from DNA  Segments of DNA comprise genes, which provides the chemical code for development  Results from the Human Genome Project have estimated that our chromosomes contain between 30,000 to 40,000 genes  The zygote doesn’t remain a single cell for long, it quickly divides at an exponential rate until at birth, you end up with billions of different cells, each with the same 46 chromosomes inherited at conception  Monozygotic twins are genetically identical because they come from the same sperm and ovum, which formed one zygote and then split into two separate zygotes  Dizygotic twins are no more genetically similar than any two siblings because they come from two different sperm and ova and start off as two different zygotes from the moment of conception o Share around 50% of genes (same as any two siblings)  From the 23 pairs of chromosomes, 22 are called autosomes and are similar in males and females rd  The 23 pair of chromosome determines a person’s gender o A female carries two X chromosomes, while a male carries an X and a Y chromosome o The mother always passes on an X chromosome, while the father can pass down either  The 46 identical genotypes in each of your cells translates into the genes that make up your genotype  The expression of the genotype into observable traits and characteristics is called the phenotype  Four main patterns of genetic expression o Simple dominant-recessive inheritance  Expression of trait is determined by a single pair of genes called alleles  One allele is inherited from each parent  Together, this pair of alleles determines the phenotypic expression for a particular trait  In a homozygous condition, the two alleles are the same and have the same effect on the phenotype  In a heterozygous condition, the two alleles are different and have different effects on the phenotype  Only the dominant allele is expressed in the phenotype  The carrier allele type, which is not expressed is recessive o Polygenic inheritance  When multiple genes are involved in the expression of a trait  Ex. Height and weight are determined by the interaction of multiple genes that add complexity o Codominance  Two dominant alle
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