The effect of mental workload on the visual field size and shape

Mental workload is known to reduce the area of one's visual held, but littl e is known about its effects on the shape of the visual held. Considering t his, the visual fields of 13 subjects were measured concurrently under thre e levels of mental workload using a Goldmann visual perimeter. Tone countin g tasks were employed to induce mental workload, avoiding interference with visual performance. Various methods of shape measurement and analysis were used to investigate the variation of the shape of the visual held as a fun ction of mental load. As expected, the mean area of visual fields reduced t o 92.2% in the medium workload condition and to 86.41% under heavy workload , compared to light load condition. This tunnelling effect was not uniform, but resulted in statistically significant shape distortion as well, as mea sured by the majority of the 12 shape indices used here. These results have visual performance implications in many tasks that are susceptible to chan ges in visual fields and peripheral vision. Knowledge of the dynamics of th e visual field as a function of mental workload can offer significant advan tages also in mathematical modelling of visual search.