Interaction of Movement Difficulty due to the Misalignment Effect and Response Latency: Connections to Fitts’ Law and Implications for System Latency Requirements

摘要

In previous reports we measured and analyzed the Misalignment Effect Function, a function describing the decrementin human performance due to rotation between operators’ display and control axes. This prior work allowed us todetermine difficulty-matched sets of rotations for a generalized 3D Fitts-like movement task. We consequently arenow able to study the interaction of system latency and movement difficulty in a highly generalized way in a virtualtelerobotic environment using wide variety of conditions and targets. Our targets are located on a spherical shell nearour participants’ starting point in a high dynamic fidelity virtual environment. Analysis of participants’ ability tomake movements to these targets has revealed a purely multiplicative interaction between control latency and taskdifficulty. Interestingly, we show that this the observed interaction supports work on Fitts’ Law by E.R. Hoffmannand that it depends upon accounting for an internal human processing latency of ~250 ms. Our data suggest that theinteraction varies nonlinearly due to task difficulty in a manner consistent with Hoffmann’s results. We propose a descriptiveequation to reflect the observed interaction that can be seen as a spatiotemporal generalization of Fitts’ Law.Our results provide a basis for generalizing latency requirements for reference tasks that may be varied in difficulty ina manner analogous to the Fitts’ Index of Difficulty.