Reading and studying on electronic devices has become more and more common. Although electronic devices greatly simplify our lives, it is well known that they can cause eyestrain and headaches and lead to poor reading comprehension. The link between visual environment and cognitive performance are the object of many research studies. The decline in comprehension when reading from an electric device might be due to poor concentration levels or different sensory processing circuits, which might be associated with physiological states, including brain and physiological activity levels. Even if the content of the text is the same, reading comprehension may be different depending on the visual context.
An experiment measured respiration and prefrontal cortex activity during reading.
A recent study of the Department of Physiology of Showa [1] reports interesting results obtained on a sample of 34 university students. During the experiment students read a novel both on a smartphone and a paper. They were asked to read the given novel on the allocated medium during the reading session. During resting state sessions, participants were asked to open their eyes and look at a wall. Subsequently, they took a reading test consisting of ten questions related to the contents of the novels. They were also asked to breathe through their nose during all sessions. There was no limit on reading time, and two min was spent in the resting state before/after reading. Participants wore a band on their forehead to measure brain activity and a mask around their mouth and nose to measure respiration. Near-infrared spectroscopy (NIRS) consisted of two probes for the measurement of brain activity, which took measurements from the left and right prefrontal cortex. The NIRS calculated oxygenated hemoglobin concentration on the forehead. The amount of oxidized and deoxidized hemoglobin was estimated by quantifying the spatial slope of light scattering and transmission in body tissues.
Reading on smartphones leads to a comprehension decline.
The findings show that reading on a smartphone resulted in lower reading performance than reading using a paper medium, as demonstrated by previous research.
Respiratory results showed that the average tidal volume decreased and breathing became shallow and fast during reading regardless of the medium, while the number of sighs reduced during reading on a smartphone compared with that during reading using a paper medium, even though the same reading behavior was being performed. NIRS data show that prefrontal activity in both smartphone and paper was increased during reading session compared to that during a resting state before reading regardless of the medium.
But it is evident that during reading, the brain activity when using a smartphone was increased compared to that when using a paper medium. Furthermore, the number of sighs increased during cognitive reading activity on a paper medium and decreased when reading on a smartphone. This finding suggests that reading on a smartphone may have caused inhibition of sighs compared to reading on a paper medium.
Activity, particularly on the left side, may reflect the predominant activity of the left hemisphere for processing reading. Overactivity in the prefrontal cortex has reportedly been associated with poor narrative content comprehension in various subjects. The results of the present study showed that overactivity in the prefrontal cortex was observed with smartphone use compared to that when using a paper medium, and the results of lower cognitive performance supported this finding [1].
Generally, increased activity in the prefrontal cortex suggests that the brain underwent a cognitive load. However, overactivity in the prefrontal cortex suggests that the brain was under heavy cognitive load. Regarding reading on a paper medium, moderate cognitive load may have generated sighing (or deep breaths), which appear to restore increased respiratory variability and control of prefrontal brain activity. In contrast, when reading on smartphones, intense cognitive load may have inhibited sigh generation, causing overactivity in the prefrontal cortex. Furthermore, a path analysis suggests that the interactive relationship between sigh inhibition and overactivity in the prefrontal cortex causes the comprehension decline.
One possible reason of comprehension decline is blue lights.
But what causes the decrease in sighing incidence using a smartphone? One of the possible causes of this is the blue light emitted by smartphones.
Intrinsically photosensitive retinal ganglion cells (ipRGCs) that respond to blue light, project to various brain regions such as the peri-habenular nucleus, which modulate arousal and learning. Blue light also causes forced sustained attention. Recent epidemiological studies focused on the link between exposure to blue light from smartphones and increased arousal and anxiety. The decreased sighing and brain overactivity in smartphone use may be caused by sustained cognitive load in ipRGC activity due to blue light exposure.
Further research is needed to examine the hypothesis of blue light effects on respiration and brain activity. Moreover, the authors suggest to deepen the possible solutions to limit the negative effects of smartphones if confirmed. For example, it may be beneficial to take deep breaths while reading since sighs, whether voluntary or involuntary, regulate disordered breathing.
[1] Reading on a smartphone affects sigh generation, brain activity, and comprehension; Motoyasu Honma, Yuri Masaoka, Natsuko Iizuka, Sayaka Wada, Sawa Kamimura, Akira Yoshikawa, Rika Moriya, Shotaro Kamijo & Masahiko Izumi Motoyasu Honma*, Yuri Masaoka, Natsuko Iizuka, Sayaka Wada, Sawa Kamimura, Akira Yoshikawa, Rika Moriya, Shotaro Kamijo & Masahiko Izumi Motoyasu Honma*, Yuri Masaoka, Natsuko Iizuka, Sayaka Wada, Sawa Kamimura, Akira Yoshikawa, Rika Moriya, Shotaro Kamijo & Masahiko Izum– Nature, Scientific Reports; (2022), 12:1589.
