de Grosbois John, Heath Matthew, Tremblay Luc
Faculty of Kinesiology and Physical Education, University of Toronto Toronto, ON, Canada.
School of Kinesiology, University of Western Ontario London, ON, Canada.
Front Psychol. 2015 Jun 16;6:800. doi: 10.3389/fpsyg.2015.00800. eCollection 2015.
Fitts' (1954) classic theorem asserts that the movement time (MT) of voluntary reaches is determined by amplitude and width requirements (i.e., index of difficulty: ID). Actions associated with equivalent IDs should elicit equivalent MTs regardless of the amplitude and/ or width requirements. However, contemporary research has reported that amplitude-based contributions to IDs yield larger increases in MTs than width-based contributions. This discrepancy may relate to the presence of augmented terminal feedback in Fitts' original research, which has not been provided in more recent investigations (e.g., Heath et al., 2011). To address this issue, participants performed reaching movements during two sessions wherein feedback regarding terminal accuracy was either provided or withheld. It was hypothesized that the absence of augmented terminal feedback would result in a stereotyped performance across target widths and explain the violation of Fitts' theorem. Yet, the results revealed distinct influences of amplitude- and width-based manipulations on MT, which also persisted across feedback conditions. This finding supports the assertion that the unitary nature of Fitts' theorem does not account for a continuous range of movement amplitudes and target widths. A secondary analysis was competed in an attempt to further investigate the violation of Fitts' Law. Based on error rates, participants were segregated into accuracy- and speed-prone groups. Additionally, target's IDs were recalculated based on each participant's performance using the effective target width (i.e., IDWe) instead of the nominal target width. When using MT data from the accuracy-prone group with this IDWe, the aforementioned violation was alleviated. Overall, augmented terminal feedback did not explain the violation of Fitts' theorem, although one should consider using the effective target width and participant's strategy in future investigations.
菲茨（1954年）的经典定理断言，随意伸手动作的运动时间（MT）由幅度和宽度要求决定（即难度指数：ID）。与同等ID相关的动作，无论幅度和/或宽度要求如何，都应引发同等的MT。然而，当代研究报告称，基于幅度对ID的影响相较于基于宽度的影响，会使MT有更大幅度的增加。这种差异可能与菲茨原始研究中存在增强的终端反馈有关，而在最近的研究中（如希思等人，2011年）并未提供这种反馈。为解决这个问题，参与者在两个阶段进行伸手动作，其中一个阶段提供关于终端准确性的反馈，另一个阶段则不提供。据推测，缺乏增强的终端反馈会导致在不同目标宽度上出现刻板的表现，并解释对菲茨定理的违背。然而，结果显示基于幅度和宽度的操作对MT有明显不同的影响，且这种影响在不同反馈条件下都持续存在。这一发现支持了这样一种观点，即菲茨定理的单一性质无法解释连续范围内的运动幅度和目标宽度。进行了一项二次分析，试图进一步探究对菲茨定律的违背情况。根据错误率，将参与者分为倾向于准确性和倾向于速度的两组。此外，基于每个参与者的表现，使用有效目标宽度（即IDWe）而非名义目标宽度重新计算目标的ID。当使用倾向于准确性组的MT数据和这个IDWe时，上述违背情况得到了缓解。总体而言，增强的终端反馈并不能解释对菲茨定理的违背，不过在未来的研究中应考虑使用有效目标宽度和参与者的策略。
