Abstract
Differences in behaviour and cognition have been observed in different human populations. It has been reported that in various types of complex visual task, eye movement patterns differ systematically between Chinese and non-Chinese participants, an observation that has been related to differences in culture between groups. However, we confirm here that, in healthy, naïve adult Chinese participants, a far higher proportion (22%) than expected (1–5%) exhibit a pattern of reflexive eye movement behaviour (high numbers of low latency express saccades) in circumstances designed to inhibit such responses (prosaccade overlap tasks). These participants are defined as “express saccade makers” (ESMs). We then show using the antisaccade paradigm, which requires the inhibition of reflexive responses and the programming and execution of voluntary saccades, that the performance of ESMs is compromised; they have higher antisaccade directional error rates, and the latency distributions of their error saccades again exhibit a higher proportion of low latency express saccade errors consistent with a reduced ability to inhibit reflexive responses. These results are difficult to reconcile with a cultural explanation as they relate to important and specific performance differences within a particular population. They suggest a potential unexpected confound relevant to those studies of Chinese versus other groups which have investigated group differences using oculomotor measures, and explained them in terms of culture. The confirmation of higher numbers of ESMs among Chinese participants provides new opportunities for examining oculomotor control.
Highlights
Over the last decade, cognitive and behavioural differences between human populations have been reported in a wide range of studies [1,2,3,4,5,6]
In circumstances which greatly decrease the occurrence of express saccades – prosaccade overlap tasks in which a central fixation target remains present when the saccade target appears - we found that 29% of Chinese participants persisted in producing high numbers of Express saccades (ES)
We observed a high number of individual frequency distributions histograms (Figure 1A,B) in which there was a clear early latency peak, centred close to 100 ms (Figure 1B; all the individual frequency distributions histograms are shown in Supporting Information as Figures S1 and S2)
Summary
Cognitive and behavioural differences between human populations have been reported in a wide range of studies [1,2,3,4,5,6]. In circumstances which greatly decrease the occurrence of express saccades – prosaccade overlap tasks in which a central fixation target remains present when the saccade target appears - we found that 29% of Chinese participants persisted in producing high numbers of ES compared to only 3% of the UK group. Confirmation of high numbers of ESMs among Chinese participants would provide a new avenue for the investigation of population differences as well as a means of investigating ESMs in greater numbers than previously possible It would imply a possible confound in experiments which have found differences in eye movement patterns between Chinese and non-Chinese groups and attributed them to culture [19,20]. Antisaccade task performance is critically dependent on a number of cortical areas, the frontal eye fields (FEF) and dorsolateral prefrontal cortex (dlPFC) [23]
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