Quantifying Differences among Ten Fingers in Force Control Capabilities by a Modified Meyer Model

Abstract

Quantifiable differences among fingers in force control capability have both important practical and theoretical values in characterizing force control of accurate finger-tapping tasks. Following the classical Fitts' law paradigm, we quantified the differences among ten fingers in term of speed-accuracy trade-off (SAT) in performing repetitive discrete force control tasks. Visual cues displaying targeted force magnitudes and tolerances were provided. Users were required to apply the targeted force within the given tolerance quickly and accurately by pressing a force sensor using the specified finger. We found that ten fingers obeyed the Meyer model in the SAT performance and they differed in reaction time, the index of performance (IP), and the goodness of fit for the Meyer model. A modified Meyer model was proposed to quantify the difference between ten fingers in the SAT performance using only one parameter, making the quantification easier than using the original Meyer model. Pairwise comparisons showed that the differences between symmetrical fingers on both hands were insignificant except for the pair of index fingers. These findings provided us with multiple perspectives on the differentiation among ten fingers in the force control capabilities. Our study helps lay the foundation for engineering systems that rely on finger force control ability.

Interfinger Synchronization Capability of Paired Fingers in Discrete Fine-Force Control Tasks

“…The experimental tests were conducted one by one to verify the two hypotheses, respectively, in two types of two-finger fine-force tasks. Our previous study confirmed that the performances of single-finger pressing were nearly equal for index and middle fingers in a discrete force control task (Peng et al, 2019). Consequently, in the current study, the index and middle fingers were employed as tapping fingers to minimize the difference between individual fingers.…”

“…As shown in Figure 1, a customized platform for multifinger force acquisition was modified based on the single-finger force measurement system used in previous research (Peng et al, 2019). For each finger, the amplitude of finger force was measured by a force sensor (FSG15N1A, Honeywell International, Inc., Morris Plains, NJ) embedded in a customized rectangular box.…”

“…Thus, three task types were defined with the target-centered ranges and [3, 0.3]. The index of difficulty of tasks was defined as index of difficulty = p A/W in Meyer formula deriving from Fitts' law (Peng et al, 2019). As a result, the task difficulty level of discrete force control was constant at 3.16 for every tapping finger.…”