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PSYB32H3 (614)


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Mark Schmuckler

Psyb20- lec 4 Normative sequence of reaching -a moving object required more -they gotta predict where the object is going, timing is important -von hofsten and grabbing moving objects -infants between 12 and 24 weeks and wanted to find out how well they reached moving objects at different speeds -he coded infants behavior, what age to they reach or just make contact what age did they grab it an how this behavior varied with diff speeds -generally the number of times they just touched the object was very high when they were young -grasp was low at young age but increased with age -number of misses is constant across age, pretty low -they are pretty good at grasping a hold of the object at 16-20 weeks of age -they are successful at reaching a moving object at the same time as reaching and grasping a non moving object -reaching by in large was predictive of these objects -they showed degree of perceptive motor behavior -we are talking about reaching with the hands, but in fact cant they reach with their feet Reaching with hands vs feet -galloway and thelen -took a longitudinal study 8-15 weeks -easily move their feet and arms and presented object midline of arms and midline of hips -they found that the average age that infants made contact with the object was earlier with the feet than with their hands -they looked at the time the infant spent in contact with the object as well -they had more extended contact with their feet with the object than with their hands -2 weeks before they learn to grasp with their hands -why better reach with feet than hands, basic difference in anatomy,the range of movement that is critical -the hips are more stable and deeper than arms and shoulder -the arms have more degrees of freedom, move in many more ways and this means that they are less controlled and feet are more controlled -havin premature infants reach with their feet help them in terms of motor development -reaching is a visually guided behavior -vision is important, because we use it to guide our hands towards it Visually guided reaching a myth -look a infants longitudinally -give them objects show them in the light or the dark -then look at the nature of the infants reaching, -if reaching is visually guided, they will reach better in the light because they will be able to visually guide their hand, they’ll see it in the light -looked at contact in the light vs dark -the whole visual guiding reaching was a myth, they did not need to see their hand to reach -just as likely to reach in the dark as in the light -doesn’t mean vision is not important -important to let you know there is an object there if it is not making sound -it provides motivation for you to reach, interesting too see wanna grab it -the actual way children reach out is not visually guided, as long as there is enough vision for the location of the object before they start reaching then they are likely to reach out the same in the light or dark Locomotion -dynamic systems-all sorts of diff components needed -muscle control, visual senses (see the world around us, judge the obstacles, property of surfaces) have to put together motor component with physical with visual to achieve Infants perception of the traversability of surfaces -property of surfaces are important -walking infants need a particular type of surface- rigid to maintain balance -if your crawling don’t need that -latency had to to with the amount of time infants spent on the starting platform, before they ventured off onto the waterbed surface -how much time did they spend looking at the surface -how much time did they spend feeling the surface -displacement behavior, behavior that was direceted away from the experiment, included crying whining, trying to climb out the apparatus -how did infants locomote, did the walking infants try to crawl or walk -the walking infants crawled across the water bed and rigid surface crawlers crawled and walkers walked -both the latency measure and displacement measure there were large increase in them in water surface compared to rigid surface -they could distinguish between the surfaces -spend more time exploring water bed vs rigid surface for both crawlers and walkers -know to choose rigid surfaces -if we are gonna walk through the world we are gonna have to maintain our upright posture -this is driven by the ability of various muscular systems -walking depends on physical system --and also visual information Visual control of posture -gives us a sense of movement -moving room apparatus -3 walls and ceiling that hung down from roof, the floor was the actual floor -you could swing the room floor stays stationary -it gives u the sense that you’ve moved -if the room moves forward you think you’ve moved back so you compensate by moving forward -newly standing infant they will also perceive the world has moved so they compensate and because they are unsteady they will overcompensate and fall over -finger tip contact stabilizes u in moving room experiment Visually guided locomotion -when walking through a crowded world there are many things that need to be taken into account -infants were much more likely to fall when they had to guide themselves (moving round the obstacles) through the world -using vision to control balance gets better as they get older -did they try to step over the barrier, did they know it was a barrier…. -see if they knew how to react when the barrier was moved up in height, learning to step over -can be successful, walk over and step over it without falling -they can fail, walk up and fall over it -refusals, they walk up to the barrier say they can do it and walk away the opposite way -older children get over higher barriers than lower, and they are more likely to show successes than youngers over higher heights -very few failures, but they increase as the bar gets higher -as the barrier gets much higher they stop even trying to cross -when they bar is low the refusals are low but increases are the bar increases How many times they try to cross and how many trials were success fail or refusal -barriers below threshold go ratio will be 1 -go ratio is higher when the threshold height is lower -infants will eventually stop trying when its over the threshold -they can understand the heights of barriers they can and cannot cross A systems
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