ANTASID: A Novel Temporal Adjustment to Shannon's Index of Difficulty

Shannon's Index of Difficulty ($SID$), a logarithmic relation between movement-amplitude and target-width, is reputable for modelling movement-time in pointing tasks. However, it cannot resolve the inherent speed-accuracy trade-off, where emphasizing accuracy compromises speed and vice versa. Effective target-width is considered as spatial adjustment, compensating for accuracy. However, for compensating speed, no significant adjustment exists in the literature. Real-life pointing tasks are both spatially and temporally unconstrained. Spatial adjustment alone is insufficient for modelling these tasks due to several human factors. To resolve this, we propose $ANTASID$ (A Novel Temporal Adjustment to $SID$) formulation with detailed performance analysis. We hypothesized temporal efficiency of interaction as a potential temporal adjustment factor ($t$), compensating for speed. Considering spatial and/or temporal adjustments to $SID$, we conducted regression analyses using our own and benchmark datasets in both controlled and uncontrolled scenarios. The $ANTASID$ formulation showed significantly superior fitness values and throughput in all the scenarios.