<p> Considerable controversy exists about how motor skills come to be represented in memory as a product of practice. One line of research advocates specificity effects, whereby skills are considered highly specific to the conditions under which they are learned. An alternative view suggests that motor control is flexible and non-specific; that motor skills are represented in a more general manner, whereby the representation is an abstraction of the products ofpractice. Although experimental findings exist that support both specificity and generality of motor skills, such evidence has emerged from very different experimental conditions and paradigms, making direct comparisons difficult. An important and interesting question then is what would happen if both specificity and generality effects could be documented within a single paradigm? And what could be said about motor control theory if such effects co-exist? </p>
<p> The possibility that a single memory representation may be developed for an entire class of skills (i.e., generality), but that performance of one member of that class may be distinguished from the rest (i.e., showing specificity effects) was examined. The basketball set shot (characterized by the feet remaining planted on the floor during execution) performed by highly-skilled players represents such a class of skills. Skilled performers have massive numbers of practice attempts of the set shot, however taken predominantly at 15-ft. (free-throws from the foul-line), with only minimal practice at other locations (in front of and behind the foul-line or at different angles to the basket). The six experiments presented here examined the nature of learned memory representation of the basketball set shot in highly skilled players. </p>
<p> In an initial series of experiments, skilled basketball players were required to perform a series of shots from several target locations spanning 9-to 21-ft. in line with the basket, including the foul-line at 15-ft. This task was completed using two different types of basketball shots (set shots; Experiments 1and2,jump shots; Experiment 3). Results revealed that set shot performance at the 15-ft. location was significantly better than predicted by a regression equation based on the performance at the other locations in Experiment 1 and replicated in Experiment 2. However, the superior performance at the foul line was not found in novice players (Experiment 2b) or when individuals performed jump shots (in Experiment 3). Instead, performance was accurately predicted by the regression equation. We suggested that a massive amount of practice accrued over many years of basketball shooting establishes the free throw as an especial skill -one that represents a highly specific capability among the general class of set-shot skills. </p>
<p> In a follow-up series of experiments, we examined potential mechanisms underlying the emergence of the especial free throw skill with an attempt to reconcile our findings with theories of motor control. In Experiments 4 and 5 two possible explanations for the specificity effect were examined: the visual-context hypothesis (unique visual context including the visual distance and visual angle to the basket) vs. the learned-parameters hypothesis (over learned specifications for the parameterizations of the set shot at 15 ft). In Experiment 4, skilled players performed set shots from the foul line (15 ft) and locations that were equidistant (15ft) but at different angles to the basket (15°, 30°, 45° to the left and right of the foul line). Performance of the set shot at the foul line was superior to the other locations, which is consistent with our previous specificity findings. In Experiment 5, players performed set shots and jump shots at the foul line and at player-chosen "favorite" locations on the court. A double dissociation was found: performance of the set shot was superior to the jump shot at the foul line but was inferior to jump shot performance at the players' favorite locations. These results are contrary to the learned-parameters hypothesis, but consistent with the visual-context hypothesis. In our last experiment, invariance in the timing structure of set shot execution of skilled players was examined to determine if the free throw was represented by the same or a distinct generalized motor program. Results revealed that the especial free throw is not represented in memory by a separate motor program compared to other set shot skills. </p>
<p> Overall, these experiments provided evidence that the free-throw is an especial skill, one which, as a result of massive amounts of practice, has a special status within a generalizable class of motor skills, and which is distinguished by its enhanced performance capability relative to the other members of the same class. The co-existence of skills represented by both specificity and generality effects have theoretical and practical implications which are discussed and warrant further investigation. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/17334 |
| Date | 03 1900 |
| Creators | Keetch, Katherine M. |
| Contributors | Lee, Timothy D., Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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