Heath Matthew, Weiler Jeffrey, Marriott Kendal A, Elliott Digby, Binsted Gordon
School of Kinesiology, University of Western Ontario, London, Ontario, Canada.
Can J Exp Psychol. 2011 Dec;65(4):259-68. doi: 10.1037/a0023618. Epub 2011 Jul 4.
The classic theorem of Fitts (1954) asserts that the combined effects of movement amplitude and target width (index of difficulty: ID) define movement times (MTs) for goal-directed reaches. Moreover, Fitts' theorem states that reaches yielding the same ID produce equivalent MTs regardless of the response's amplitude and width combination. However, most work providing direct support for Fitts' theorem has employed short movement amplitudes and small target widths. Thus, no direct evidence supports the unitary nature of MT/ID relations across a range of amplitudes and widths used in contemporary studies of goal-directed reaching. To that end, we contrasted MT/ID relations for discrete reaches equated for movement ID but differing with respect to their amplitude (15.5, 19, 25.5, and 38 cm) and width (2, 3, 4, and 5 cm) requirements. Results show that amplitude and width manipulations yielded robust linear MT/ID relations; however, the slope of the MT/ID function was markedly steeper in the former (amplitude=92 ms; width=13 ms). Such findings indicate that the constituent elements of movement ID are dissociable and that the fixed parameter nature of Fitts' theorem cannot be applied to a continuous range of veridical movement amplitudes and target widths.
菲茨（1954年）的经典定理断言，运动幅度和目标宽度的综合影响（难度指数：ID）决定了目标导向性伸手动作的运动时间（MT）。此外，菲茨定理指出，无论动作的幅度和宽度如何组合，产生相同ID的伸手动作都会产生相等的MT。然而，大多数直接支持菲茨定理的研究都采用了较短的运动幅度和较小的目标宽度。因此，没有直接证据支持在当代目标导向性伸手动作研究中所使用的一系列幅度和宽度范围内，MT/ID关系具有单一性。为此，我们对比了离散伸手动作的MT/ID关系，这些动作的运动ID相等，但在幅度（15.5、19、25.5和38厘米）和宽度（2、3、4和5厘米）要求上有所不同。结果表明，幅度和宽度的操作产生了稳健的线性MT/ID关系；然而，MT/ID函数的斜率在前一种情况下（幅度=92毫秒；宽度=13毫秒）明显更陡。这些发现表明，运动ID的组成要素是可分离的，并且菲茨定理的固定参数性质不能应用于连续范围的真实运动幅度和目标宽度。
