Thursday, 20 October 2011

Learning to throw to max distances: Do changes in release angle and speed reflect affordances for throwing?

Adults skilled at long distance throwing, able to pick optimum weight for max. distance (Bingham et al, 1989), but replicated and results from a larger range of object sizes and weights recorded (Zhu et al, 2008). A very functional relation between size and weight was established.
Zhu et al. investigated whether people without good throwing skills could perceive the affordance for throwing and if they would learn to. They were unable to select optimal objects for throwing with any accuracy, but once learned to throw for distance; could then see the affordance.
Affordance property - optimal distance of throws determined by initial angle and speed.
Hypothesis - object size and weight might affect dynamics of hefting in similar ways and that this similarity would allow hefting to provide information about affordance.
Study was performed for perceptual learning of the affordance while learning to throw and to study concurrent changes in the kinematics of throwing.
48 objects varying in size (marble to waterpolo ball)
18 Indiana Uni students that could throw but not at a competitive sporting level.
Ps were scheduled for 3mnths throwing practice randomly divided into 3 groups using ANOVA on throwing data gathered from pre-test.
Results: Mean distances of throws each of 6 objects for each group, during each week of practice and after practice, plotted against objects.
(1) Distance of throws - Distance increased after practice for all groups.
(2) Release angle - Throwing practice didn't yield significant changes in release angle, however consistency of release angle did increase amongst participants.
(3) Release speed - Mean release speed increased by as much as 50%, however each group exhibited different patterns.
(4) Distance vs Release Angle/Release Speed - Release angle not significant for systematic changes in distance. Release speed was significantly correlated with distance of throws.
(5) Effect of object size and weight on throwing - Object size does affect reliability with which near optimum release angles were produced. Size had no effect on mean angles of release or significant effect on distance of throw.

1 comment:

  1. This is a sensible set of notes from that paper, but I want you to take this and post a summary written in complete sentences, focusing on the bigger picture. Aim for, say, 300 words, and don't talk about ANOVAS, etc; stay on summarising the aims and results.

    A couple of things:
    A very functional relation between size and weight was established.
    Specifically? As a rule, you can't just say this sort of thing because when someone reads it, they immediately want to know more and you haven't given it to them. So you must always be as specific as possible.

    Affordance property - optimal distance of throws determined by initial angle and speed.
    Careful here. The task is to throw to a maximum distance; the affordance property to be perceived is the size-weight combination that allows the thrower to produce that maximum distance. For a given object size, people throw different weight objects different distances.