How do you know when to blink? A study shows that blinking does more than keep your eyes moist; your brain is actually timing your blinks around sentences, surprises, and the flow of a story.
Study: The timing of spontaneous eye blinks in text reading suggests cognitive role. Image credit: Doucefleur/Shutterstock.com
Ghent University published a study in Scientific Reports that identified the cognitive role of spontaneous eye blinks during text reading.
Background
Spontaneous eye blinks are involuntary eye movements that are not a reflex response. This involuntary blinking is vital in lubricating the eyes and preventing them from drying out. In humans, the average eye blink rate is 15 blinks per minute. However, the rate changes with age and varies across individuals.
Blinking is associated with the brain’s cognitive processing. In addition to biological needs, a reduction in blink rate has been observed during tasks with high cognitive demands, such as driving or controlling air traffic.
Performing tasks with high cognitive demands requires heightened attention, which is associated with a reduced blink rate. Similar effects have been observed while processing purely auditory information. These findings suggest that eye blinks serve as content-sensitive markers, irrespective of the type of sensory information. Blinks are unconsciously regulated through attentional mechanisms to optimize task performance.
Existing evidence suggests that spontaneous eye blinks are reduced during memorable scenes of a movie and increased during attentional breakpoints, such as the conclusion of an action or repeated presentations of a similar scene. This suggests that spontaneous blinking is not merely a physiological necessity, but is also actively associated with the content of the scene.
In the current study, researchers aimed to investigate whether spontaneous eye blinking plays a cognitive role during text reading.
The study
The researchers analyzed data from the large Ghent Eye Tracking Corpus (GECO), which contains eye movement data from 15 participants who silently read an entire novel. The GECO was initially designed for general eye-movement research, rather than specifically for blink analysis, so blink events were extracted from the raw eye-tracking data. They specifically assessed the impact of punctuation marks, word frequency, and word predictability on blinking patterns.
Punctuation marks denote the end of a sentence or a pause in a sentence. The researchers hypothesized that these marks could be attentional breakpoints during fluent reading, influencing the blinking pattern. They also assumed that word frequency and predictability can influence the blinking pattern, as it has been observed that the presence of unusual or unexpected words in a text increases cognitive demand.
Statistical models, including beta regression for text position effects and mixed-effects logistic regression, were used to assess how word frequency and word predictability influenced the probability of a blink. To avoid confounding with function words, only content words were used in the word frequency and predictability analysis.
Study findings
The study reported a significantly higher spontaneous blinking rate around punctuation marks than other random text positions. An increased probability of blinking was also observed at the end of a sentence or around positions where punctuation marks and line endings coincide.
Regarding word frequency and predictability, the study reported a significant reduction in blinking rate while reading words that occur more frequently in the text. In contrast, unexpected or surprising words significantly increased the blinking rate.
The analysis also revealed a significant interaction between word frequency and predictability. The effect of word predictability was most pronounced for high-frequency words. This means that when readers encounter a word that is typically common but appears in an unpredictable or surprising word context, it increases the likelihood of blinking even more than a rare word.
Not all differences between types of punctuation were statistically significant, but overall, all punctuation types were associated with higher blink rates than random positions in the text.
Study significance
The study highlights the significant cognitive role of spontaneous eye blinking during text reading. Specifically, it identifies punctuation marks, word frequency, and word predictability as major drivers of blinking patterns during reading.
As the researchers stated, this work serves as a much-needed contemporary follow-up to the original pioneering study, which investigated blink rates during reading using a manual blink count.
Loss of perceptual information during blinking is inevitable. It is generally assumed that the brain regulates blinking frequency during reading to avoid possible information loss. The observed reduction in blink rate (10 blinks per minute) compared to the generally established blink rate (15 blinks per minute) justifies this hypothesis.
The study finds an induction in blinking rate around punctuation marks, which may reflect a reduction in the incoming information load and attentional demands. This justifies a potential association between spontaneous blinking and cognitive processing.
The study also found a reduction in the blinking rate when reading high-frequency words and more predictable words. The word frequency effect indicates that high-frequency words are cognitively less demanding and require lower-level cognitive processing than low-frequency words. Similarly, the word predictability effect suggests that common (predictable) words require less cognitive processing than unexpected or uncommon words.
The interaction effect suggests that predictability matters, especially for frequent words, adding a layer of nuance to previous findings. Both effects collectively indicate that spontaneous eye blinking plays a substantial cognitive and attentional role during text reading.
While analyzing the dataset, the researchers considered the most recorded blink events to represent true blinks. However, it remains possible that some of the recorded blink events result from short-term data loss or recording errors. Although unlikely to significantly affect the study findings, these incidents may introduce additional data.
Another limitation is that the original dataset was not explicitly designed for blink research, which may have introduced further sources of noise or bias. However, the large amount of data analysis will likely mitigate the impact of such factors.
Several studies have proposed blinks as a potential tool for studying cognition and related mental processes, such as attention. However, only a few studies have scientifically suggested that blinks can be used to examine cognitive processes, specifically during reading. Given the current study's findings, researchers encourage further exploration of this possibility in future research.
They also suggest that future work could examine whether blink rates are affected by other textual features or subjective boundaries in narrative structure, as observed in video viewing studies.
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