The aim of this study was to provide a detailed account of the spatial and temporal disruptions to eye-hand coordination when using a prosthetic hand during a sequential fine motor skill. Twenty-one able-bodied participants performed 15 trials of the picking up coins task derived from the Southampton Hand Assessment Procedure with their anatomic hand and with a prosthesis simulator while wearing eye-tracking equipment. Gaze behavior results revealed that when using the prosthesis, performance detriments were accompanied by significantly greater hand-focused gaze and a significantly longer time to disengage gaze from manipulations to plan upcoming movements. The study findings highlight key metrics that distinguish disruptions to eye-hand coordination that may have implications for the training of prosthesis use.

Background: Prosthetic hands impose a high cognitive burden on the user that often results in fatigue, frustration and prosthesis rejection. However, efforts to directly measure this burden are sparse and little is known about the mechanisms behind it. There is also a lack of evidence-based training interventions designed to improve prosthesis hand control and reduce the mental effort required to use them. In two experiments, we provide the first direct evaluation of this cognitive burden using measurements of EEG and eye-tracking (Experiment 1), and then explore how a novel visuomotor intervention (gaze training; GT) might alleviate it (Experiment 2). Methods: In Experiment 1, able-bodied participants (n = 20) lifted and moved a jar, first using their anatomical hand and then using a myoelectric prosthetic hand simulator. In experiment 2, a GT group (n = 12) and a movement training (MT) group (n = 12) trained with the prosthetic hand simulator over three one hour sessions in a picking up coins task, before returning for retention, delayed retention and transfer tests. The GT group received instruction regarding how to use their eyes effectively, while the MT group received movement-related instruction typical in rehabilitation. Results: Experiment 1 revealed that when using the prosthetic hand, participants performed worse, exhibited spatial and temporal disruptions to visual attention, and exhibited a global decrease in EEG alpha power (8-12 Hz), suggesting increased cognitive effort. Experiment 2 showed that GT was the more effective method for expediting prosthesis learning, optimising visual attention, and lowering conscious controlas indexed by reduced T7-Fz connectivity. Whilst the MT group improved performance, they did not reduce hand-focused visual attention and showed increased conscious movement control. The superior benefits of GT transferred to a more complex tea-making task. Conclusions: These experiments quantify the visual and cortical mechanisms relating to the cognitive burden experienced during prosthetic hand control. They also evidence the efficacy of a GT intervention that alleviated this burden and promoted better learning and transfer, compared to typical rehabilitation instructions. These findings have theoretical and practical implications for prosthesis rehabilitation, the development of emerging prosthesis technologies and for the general understanding of human-tool interactions.

1In three experiments, we explored the use of deceptive gaze in soccer penalty takers using eye-2 tracking equipment. In Experiment 1, players competed against a goalkeeper while taking 3 unconstrained shots. Results indicated that when players used deception (looking to the opposite 4 side to which they shot) they extended the duration of their final aiming (quiet-eye; QE) fixation 5 and maintained shooting accuracy. In Experiment 2, with no goalkeeper present players still used 6 extended QE durations when using a deceptive strategy, but this time their accuracy suffered. In 7 Experiment 3, we manipulated the goalkeeper's location while controlling for the use of 8 peripheral vision and memory of goal size. Results indicated that increased QE durations were 9 required when using deceptive aiming, and that accuracy was influenced by the position of the 10 goalkeeper. We conclude that during deceptive aiming, soccer players maintain accuracy by 11 covertly processing information related to the goalkeeper's location. The ability to predict the mental state and behavioral intentions of others from their gaze 2 direction has been fundamental to our evolutionary success (Emery, 2000). Accordingly, 3humans have developed a predisposition to focus on the gaze direction of others when attempting 4 to interpret and anticipate their future actions (Blakemore, Winston, & Frith, 2004). For example, 5Nummenmaa, Hyona and Hietanen (2009) have shown that pedestrians use eye-movements to 6 indicate their intended direction of travel, and that approaching pedestrians use this information 7 to avoid collisions. However, the predisposition to focus on the gaze of others can be exploited 8 through the use of deceptive gaze behaviors that aim to disguise the deceiver's future intentions 9 (Emery, 2000). Such deceptive behaviors are readily observable in sport (Güldenpenning, Kunde 10 & Weigelt, 2017). 11In a sporting context these deceptive behaviors are often referred to as 'head-fakes ' (e.g., 12 Basketball; Kunde, Skirde & Weigelt, 2011) and are characterized by performers faking gaze in 13 one direction whilst shooting or passing to another. At the heart of their use is a deliberate 14 attempt to misdirect the attention of an opponent and negatively influence their responsive 15 actions in order to create a performance advantage. Despite their frequency in sport, there have 16 been few empirical studies that have explored the cognitive factors behind their use (Kunde et al, 17 2011). Those that have done so have focused on expert and novice differences in the ability to 18 detect deceptive actions across a range of sports; including handball (Canal-Bruland & Schmidt, 19 2009; Canal-Bruland, van der Kamp, & van Kesteren, 2010), rugby (Jackson, Warren, & 20 Abernethy, 2006), basketball (Sebanz & Shiffrar, 2009) and soccer goalkeeping (Dicks, Uehara, 21 & Lima, 2011;Smeeton & Williams, 2012; Tomeo, Cesari, Aglioti, & Urgesi, 2012). The 22 consensus from these studies suggests that experts are better a...

Little is known about how human perception is affected using an upper-limb prosthesis. To shed light on this topic, we investigated how using an upper-limb prosthesis affects individuals’ experience of object weight. First, we examined how a group of upper-limb amputee prosthetic users experienced real mass differences and illusory weight differences in the context of the ‘size–weight’ illusion. Surprisingly, the upper-limb prosthetic users reported a markedly smaller illusion than controls, despite equivalent perceptions of a real mass difference. Next, we replicated this dissociation between real and illusory weight perception in a group of nonamputees who lifted the stimuli with an upper-limb myoelectric prosthetic simulator, again noting that the prosthetic users experienced illusory, but not real, weight differences as being weaker than controls. These findings not only validate the use of a prosthetic simulator as an effective tool for investigating perception and action but also highlight a surprising dissociation between the perception of real and illusory weight differences.

Safe stair negotiation is an everyday task that children with developmental coordination disorder (DCD) are commonly thought to struggle with. Yet, there is currently a paucity of research supporting these claims. We investigated the visuomotor control strategies underpinning stair negotiation in children with (N = 18, age = 10.50 ± 2.04 years) and without (N = 16, age = 10.94 ± 2.08 years) DCD by measuring kinematics, gaze behavior and state anxiety as they ascended and descended a staircase. A questionnaire was administered to determine parents' confidence in their child's ability to safely navigate stairs and their child's fall history (within the last year). Kinematics were measured using three-dimensional motion capture (Vicon), whilst gaze was measured using mobile eye-tracking equipment (Pupil labs). The parents of DCD children reported significantly lower confidence in their child's ability to maintain balance on the stairs and significantly more stair-related falls in the previous year compared to the parents of typically developing (TD) children. During both stair ascent and stair descent, the children with DCD took longer to ascend/descend the staircase and displayed greater handrail use, reflecting a more cautious stair negotiation strategy. No differences were observed between groups in their margin of stability, but the DCD children exhibited significantly greater variability in their foot-clearances over the step edge, which may increase the risk of a fall. For stair descent only, the DCD children reported significantly higher levels of state anxiety than the TD children and looked significantly further along the staircase during the initial entry phase, suggesting an anxiety-related response that may bias gaze toward the planning of future stepping actions over the accurate execution of an ongoing step. Taken together, our findings provide the first quantifiable evidence that (a) safe stair negotiation is a significant challenge for children with DCD, and that (b) this challenge is reflected by marked differences in their visuomotor control strategies and state anxiety levels. Whilst it is currently unclear whether these differences are contributing to the frequency of stair-related falls in children with DCD, our findings pave the way for future research to answer these important questions.