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PSYB20 - Lecture 5

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Marc A Fournier

Lecture 5 Oct 10  David Lee – experiment where room’s walls and ceilings moved around. If the room ‘moves forward’ you get visual info that you’ve moved backwards, thus you sway forward to compensate with loss of balance o Put kids in the room, if room moved forward they fell forward, if it moved back they fell back; big dramatic effect; demonstrates that we use visual info to control balance  Thomas Stoffregan – adults are more sensitive to movements along the side in the periphery than in the central visual field (unidirectional motion of moving back forward or back) o Kids puts in one of two conditions: full room movement or partial room movement (only front wall is moving or only side wall moving) o Huge response found when full room moved; more likely to move backwards when only the side walls move (about the same level of response when full room or side walls move)  So there’s a stronger response to movement on the sides than movement in the front  When kids start standing they use visual info to balance self  The study above was unidirectional but other studies have oscillating rooms, causing adult to move back and forth at the same speed that they’re moving. Children also sway back and forth at same speed o Child doesn’t even need to be standing to sway  Visually guided locomotion – ability of adult/child to navigate through cluttered enviro o One experiment: use pylons to see child walk curving path to get to parent, then move the room to check for postural reaction o Children show more dramatic postural reaction when in visually guided room (obstacles) this is because vision was being used in 2 conditions: balance and guiding around obstacles. o When children used vision to do these two different function at the same time, it didn’t work  In natural situation experiments – carry ball from experimenter to mom; the kid often tried to get out of the hallway even though the hallways were restricted by a 2 by 4 barrier. They just tripped over it and kept going Visual-guided Locomotion in Toddlers  Children of three ages were made to walk down a hall with a barrier to reach mom; wanted to see how the infant would pass barrier even if barrier got higher and higher  Responses coded in 3 categories: o Step over barrier successfully o Try to get over barrier but knock off the pole or break the barrier – not successful o Fail to even try; refusals were displacement behaviours  Slide 12 of the motor development slides o Top graph – at low barrier height (barrier on ground) infants show good success rate  18 mo and 24 mo are better than 12 mo Lecture 5 Oct 10 o Second graph is failure rate - Success rates decrease as height increases; failure rate increases with height o Third graph is refusal rate – initially children don’t refuse but as barrier height rises you start seeing refusal rate. But 18 months get even higher refusal rates with higher heights, meaning that children at this age have some knowledge of heights of barriers that they can or cannot get over  Each infant’s individual data was taken and a threshold height was found to find successful crossing (when they can get over 50% of the time or 75% of the time) o If infants have some idea of what they can or can’t get over, once you get over threshold they’ll stop even trying o This is exactly what was found on slide 12 (threshold = 0 on x axis)  On slide 12 – when infants aren’t trying to cross barrier, it’s a visible refusal A systems approach to locomotion  Throughout all of these studies the general idea: when talking about motor skill, we think of it as just one thing when in fact there are a number of different aspects that enter into development and growth in motor skills  Dynamic systems approach: when you’re looking at any particular skill it’s not the result of growth or development in any one unidimensional component but instead development is the result of a whole set of independent component processes  Slide 13 – schematic diagram proposed by Esther Thelen o Talks about various components that might be important for development of locomotion  So to map out one ability such as locomotion we must map out all the components in it and then see the development in each component o Each of these components will interact in determining the child’s ability to perform in locomotion tasks o Any one of these components = rate development factors (e.g., child might not have visual flow sensitivity even though they have the motivation thus they won’t be able to walk  rate development factor is the visual sensitivity because it limits the ability from growing) In summary  Motor skills are not single unitary skills but instead they have to do with development across a wide array of domains (visual parameters, etc..) o Involves integration with other perceptions Lecture 5 Oct 10 Physical Growth  Primates have an extended period of prenatal growth  Prolonged immaturity leads to increased dependency of child on adult which is important in a social context  During the first 3 months, infants gain 2 pounds per month  Growth is rapid in infancy but after infancy (elementary school etc..) it slows down; average height increases by 2 inches a year  But patterns of growth are steady Distal growth curves  Growth curve for height shows growth curve for boys and girls separately (girl = solid line; boy=solid line) o Boys show more growth in infancy, but patterns reverses because by early teens the girls short past and then the pattern reverses when boys catch up and exceed girls  Girls achieve 50% of their adult height by the time that they’re 1.75yrs old  Boys achieve 50% of adult height by age 2 Growth Curves for Body Organs  Plotted in terms of percent of adult size  We see variation in the growth of different organ systems (i.e., brain and head grow rapidly early in size, adult size by 10 yrs of age; genital system has no growth until 13 yrs of age where it shoots up with puberty)  Early in life around preteen years the lymph nodes actually get bigger than adult size then shrink backwards to hit adult size Changes in Body Proportions  Different parts of the child’s body also grow at different rates; thus changes in body proportion as child grows  Cephalo-causal: from head to lower body part o The exception: children are more accurate when reaching with feet. Children show better coordination with feet at bottom of body than they are with hands at the top of their body 
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