An eye-tracking study to assess the perception of usability affordances of assistive devices. An application to jar openers

Some assistive devices (ADs) aim to ease elders performing daily activities by changing postural and strength requirements. Elders usually have cognitive lacks too, making AD usability perception an important issue. Usability perceptions arise from the affordances conveyed by the AD: design features should act as signifiers transmitting opportunities of how to use the AD. This study assesses the perception of jar openers usability. Eye-tracking (ET) data from 56 subjects were used. Rendered images of 6 ADs were shown, in 2 versions: with and without rubber on the grip area. Each slide showed the 6 ADs, each AD image being an area of interest (AoI) to be tracked. The participants ranked the ADs in the next usability affordances: comfort, effort level, easiness to grip, easiness to use, lid slippery and robustness. For each affordance, they were eye-tracked while deciding the best AD, and afterwards they ranked the other ADs. The ranks were transformed into scores, and their correlation with ET parameters (decision time and number of fixations on each AoI) were studied, along with the effect of the rubber on the scores. Heat maps were also analyzed to identify the signifiers of the ADs that attract attention on usability. The results showed the potentiality of ET to study the perception of ADs usability affordances, and that the addition of rubber on the grip area of the jar openers or the material and shape of the lid area have an effect on their understanding and use