The timing of spontaneous eye blinks in text reading suggests cognitive role

Abstract

A growing body of research suggests that spontaneous eye blinks have a cognitive role in addition to their biological functions. Blinking has been associated with cognitive effort and with processes related to the dynamic nature of incoming sensory information, such as the release of attention. However, there is limited evidence supporting the cognitive role of spontaneous blinks, specifically during reading. This study provides the first systematic investigation of blinking patterns in eye-tracking data of naturalistic silent text reading. We hypothesized that blinks would be more likely to occur (1) around punctuation marks signaling a breakpoint in the text and (2) following fixations on lower-frequency and less predictable words. To test these hypotheses, we utilized data from the large Ghent Eye Tracking Corpus (GECO), which contains eye movement data from 15 participants who read an entire novel in silence. The results indicate higher blinking proportions at punctuation marks compared to other positions in the text. Additionally, blink rates were modulated by word frequency and predictability, with higher word frequencies and predictabilities significantly reducing the probability of blinking. Extending previous research, our findings suggest substantial cognitive regulation of blinking during reading.

Keywords: Attention; Corpus study; Eye tracking; Reading; Spontaneous eye blinks.

Fig. 1

Segment of the novel annotated with data viewer markings. An example paragraph from the novel with added Data Viewer markings. The data were segmented based on preprocessing steps, as indicated by the boxes in the figure, upon which the positions of interest were determined according to the content of these segments. The blue circles represent fixations, with fixation durations indicated, while the yellow arrows denote saccades. The red lines indicate blink activity (the length is not proportional to the blink duration). The initial step of the analysis can be demonstrated with the following example: the last red line (blink) on the fifth line is initiated after a fixation within a text segment containing an end-of-line position (position of interest). Consequently, this blink is classified as occurring in a position of interest.

Fig. 2

(a) Results of analysis 1: the impact of text position on relative blink proportion. Boxplot with midlines showing the median and box limits indicating the first and third quartile of relative blinks proportions per position of interest. The whiskers extend to the minimum and maximum value, with the exception of outliers. Lines connect blink proportions across different positions for a given participant, thereby illustrating the variation and trends in blink rates. Each coloured dot represents one participant. Four out of 6 pairwise contrasts were significant, *** = p < .001. (b) Results of follow-up analysis 1: differentiating different punctuation marks. Boxplot with midlines showing the median and box limits indicating the first and third quartile of relative blinks proportions per position of interest. The whiskers extend to the minimum and maximum value, with the exception of outliers. Lines connect blink proportions across different positions for a given participant, thereby illustrating the variation and trends in blink rates. Each coloured dot represents one participant. All pairwise contrasts including the Residual category were significant, *** = p < .001.

Fig. 3

Result of analysis 2: impact of word frequency (Zipf Values) and word predictability (Surprisal Values) on blink probability. The figure illustrates the predicted probability of a blink as a function of the word frequency score and surprisal value, as estimated by a generalized linear mixed-effects model. Predictor variables were scaled prior to model fitting. The colored lines represent the predicted blink probabilities for three distinct quantiles of surprisal (0.10, 0.50, and 0.90), while the shaded regions represent the corresponding 95% confidence intervals.