Power-law Behaviour in Eye Movements During Reading in 21 Languages

Eye movements provide insights into psychological processes. In reading research, investigating cognitive processes via differences in reading behaviour is prevalent. However, cross-linguistic universalities in eye movement behaviour during reading remain largely unknown. A recent study analysed relations between successive eye movements, designated relative saccade lengths, and found that the relations' probability distributions observe a power-law-shaped tail across various tasks and experiments, including reading in six different languages. Validating this finding and assessing its universality for further languages is essential since it could represent the first language-independent and quantifiable statistical regularity in reading behaviour. With existing data from the MECO corpus, we replicate the original study's results with further empirical data for the same six languages and extend the analyses to a total of 21 languages (N = 1299). The results show that the probability distributions of relative saccade lengths consistently observe a power-law-shaped tail across all 21 languages. Thus, our results replicate the findings of the original study's six languages and extend them to 15 further languages. This provides further empirical evidence for the probability distribution of relative saccade lengths as a possible universality in eye movement behaviour during reading. Furthermore, the slope of the probability distributions suggests that adjusting eye movement lengths during reading might constitute optimal search behaviour.