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PSYB20- Lecture 3

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Marc A Fournier

 Sometimes longitudinal designs require you to come back every weeks over a period of months, which is a big commitment on the part of people  Selective attrition – people will drop out for many reasons, which can give us a bias sample  Repeated testing – a longitudinal design by definition involves testing a person multiple times, presumably with the same test. o So you might see an improvement in scores but it could be due to the fact that they’ve been exposed to the test before rather than developmental change  Longitudinal designs examine development of a particular cohort, meaning that you’re examining the development of particular people in time. o Children born in the same time are influenced by the historical/cultural difference of the time period they were born in.  cohort effect  Cross-sectional designs tests different groups of different ages and then you test them all at the same time o It’s much less time consuming and less expensive than a longitudinal study thus correlation is extremely efficient o You don’t have to worry about repeated testing or selective dropout effects because subjects just have to do the study once o Conceptual problem of cross-sectional design: it doesn’t actually provide evidence about change at the level of the individual because we haven’t measured change in a single individual, we’ve measured change across two different groups of individuals instead. o Differences between people in each group is a problem, even if you try to selectively match the individuals of each group. o Cohort effects are still present; comparison of the different age groups is problematic because they were all born in different years which are potentially different periods in history. Differences between groups may not be due to developmental differences but rather due to that cohort effect difference o Cohort effects in cross-sectional study may not matter if you’re dealing with babies of different months apart but drawing the boundary at what time frames make a generation is important.  Intellectual functioning of individuals in a study had a curve to it (increase until age 20 then steady and then decrease as you age) according to the cross-sectional results. In a longitudinal study there wasn’t a drop in IQ, instead there was increase until age 20-30 and it just stayed the same  Sequential strategy essentially integrates features of both cross-sectional and longitudinal comparisons at the same time o You conduct both cross-sectional and longitudinal design. o It’s when you have different groups of ages and then you follow each group longitudinally o During the second cross-sectional portion, bring in new groups of each age and use them as a control for ever respective age group (so if your group is now 10 years old, get a new group of 10 year olds)  You can still have attrition problems in sequential strategies but it’s still a powerful design that’s being used more  In Comparative Research – attempt to learn something about human development by studying and attempting to explain the development of other animal species o This grew out of the ecological approach o Comparative studies are powerful because it also allows you to do controlled tests of hypotheses that would be problematic to do with humans (this is controversial in terms of ethics) For example, if you want to see what is the impact of no vision stimulation during development you could use cats or animals instead of humans  Cross-cultural research – attempts to look at the issue of the generalizability of our findings o We want to know if the results of our experiments are truly universal o Cross-cultural research tests participants from different cultural backgrounds and the results are compared. If they’re the same results it allows us to have confidence in the generalizability in the results we’re seeing. o Cross-cultural research has started to focus more so on differences between cultures rather than similarities General Problems with Research and Developmental Research  Contamination – could occur due to groups drawn from different SES or ethnic backgrounds. The results would end up being a result of other factors that you’re not looking at  Researcher effects – may be unintentional, race of experimenter may play a role in the nature of the responses that participants give. o A study on sexual assault in university women and their responses may be influenced by gender of experimenter o In demand characteristics – the researcher gives subtle clues as to how they want their participant to respond  Reconstruction through retrospection – much more focused on development. o E.g., Freud had adult patients and asked them to talk about their childhood memories but the problem is that memories may not be correct, subjects reconstruct their past when trying to recollect it thus accuracy must be questioned o When it comes to the milestones kids have, from crawling to standing to walking etc.. parents remember these things but sometimes the parents may remember them wrong (like saying the kid started crawling at 2 months and walking by 7 months)  Faulty logic – Proper logic must be applied rigorously when it comes to deductive reasoning o E.g., boats float on water and so does x thus we conclude that x is boats but this isn’t right, other things can potentially float on this isn’t a proper logical conclusion o Developmental events are timed. If we see that developmental event A precedes developmental event B, it’s tempting to say that A is a precursor to B and there’s a relationship between the two. However, this isn’t a logical conclusion because A and B could be driven by some other event.  Inadequate definition of concepts – concepts have to be defined and reliably measured o We have a concrete concept of things like weight, car, bought etc.. but the problem is that other concepts that we might be interested in are abstract. For instance the concept of aggression is abstract so our ability to understand this depends on the way we define (operationalize) the concept of aggression and the way we measure them o It’s critical to precisely define our concepts so that even if people disagree with your view on aggression, they at least know exactly what you were measuring  Sampling – has to do with type or participants we get in our research o The racial background of participants could have an important impact on the nature of the findings.  Overgeneralization – we apply the results more broadly than we should o Even if our findings are reliable and significant, lots of the time we will end up overgeneralizing Gene-Environmental Interactions  There are 2 huge critical factors on children’s development: Genetics (heredity) vs Environment o Each has the power to alter the course of development  Generally, contemporary researchers agree that genes and environment are equally involved n all aspects of development  The question is, how much do environment and genes play a role? Like in personality, how much is due to genes and due to environment? o If genes and enviro interact you can’t really say how much of one is responsible compared to the other  Genotype and phenotype talk about the levels on which we can think about affect of genes and enviro on behaviour  Phenotype is due to complex gene and enviro interactions o Focuses on organisms as they develop o Has to do with characteristics of behaviour  Problem: we often make inferences on the genetic structure of a person based on phenotype o It’s impossible to fully disentangle genetic from environmental effects  Variations in the environment at any level can have immediate effects on the development of phenotypes.  The Himalayan rabbit is black with a white torso; researchers found that if they removed some of the white fur and placed an ice pack on the spot, the fur grew back black instead of white. This suggests that fur colour depends on temperature at the specific site of growth. So the gene for black fur was expressed at lower temperature than the gene for white fur. o Rabbit’s extremities are colder thus are black whereas torso is warmer thus is white  Changes in phenotype are to be charted as a function of the variation as genetic structure or environment to give all possible relationships betweens gene and enviro o Ideally you want to have a really big environmental range Waddington’s Canalization Principle  Behaviour that is strongly canalized develops similarly across a wide range of environments. To move it out of that canalized path you need an extremely strong environmental influence  Examples of highly canalized abilities in humans such as perceptual and motor developments: all human infants reach the same perceptual and motor milestones at about the same age, they go through the same path (roll over, crawl, stand walk etc..) regardless of environment o In this case development could be changed but you’d need a dramatic environmental influence  Language development in some ways is another example of canalized ability; for instance when babies babble, all infants around 8-10 months of age begin to babble even deaf infants o Environment does have an infant because what happens is that deaf infants eventually stop whereas normal infants continue. Thus environment influences course of babbling  Environment has relatively little impact thus is must be strong to have an effect on canalization  Canalization ensures that certain aspects of child development are constant under a wide range of environments and this is important because it promotes survival  In the graph on slide 6  range of reaction principle o Child A has high genetic potential, Child B has medium genetic potential and Child C has lowest genetic potential o Taking Child A and putting him in a restrictive environment they don’t perform well but in an enriched environment they do really well, same goes for Child B and C across different ranges o Child A has the widest reaction rate  child with greatest genetic potential has greatest potential range as to where they’re going to fall o Child C  child with lowest genetic potential has lowest range o Child B could outperform child A, and Child C could even outperform child B
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