Dissecting errors made in response to externally- and internally- driven visual tasks in the common marmosets and humans

Various visual paradigms in oculomotor research were proposed and proven effective for studying the neural processes of eye movement, cognitive control, attention and neurological disorders. However, oculomotor researchers usually analyse data collected from humans or over-trained non-human primates (NHPs), focusing only on successful records, whereas error records are usually excluded. In diseased conditions, these errors may repetitively show up but their interpretation would be difficult due to the absence of baseline records reported from healthy controls. In the current study, we aimed to analyse both failure and success and to compare marmosets and humans. We trained marmosets to perform the externally-driven gap saccade task and the internally-driven oculomotor delayed response task. We also collected data from human subjects who performed identical tasks. We categorised error trials into three different groups, depending on when the task instructions were violated, and interpreted possible causes based on saccade reaction time, saccade landing position and task history. We found that marmosets and humans showed remarkably similar behaviour in both error and success, despite the rareness of humans’ failure. Finally, we found that successful saccades in gap saccade task had always the highest peak velocity in both species, reflecting faster sensorimotor processes for correct responses. Our results suggest that when performing oculomotor tasks, marmosets may share similarities to humans’ neural processing of success and errors, making them a suitable model for studying humans. More importantly, analysing error trials in sync with successful ones provides further insights into the cognitive and sensorimotor processes.