Compared with people who occasionally use only one media device, those who often use several media devices at the same time have lower gray-matter density in a brain region involved in cognitive and emotional control.
The research, conducted in the Sackler Centre for Consciousness Science at the University of Sussex in the UK, is published in the journal PLOS ONE.
Neuroscientists Kep Kee Loh and Dr. Ryota Kanai found that compared with people who occasionally use only one media device, those who often use several media devices at the same time have lower gray-matter density in the anterior cingulate cortex - a brain region involved in cognitive and emotional control.
For their study they looked at functional magnetic resonance imaging (fMRI) brain scans of 75 adults who had completed a survey about their use of media devices such as cellphones, computers, television and print media.
The participants had also completed assessments of what psychologists call the "Big 5" personality traits: extraversion, agreeableness, openness, conscientiousness and neuroticism.
Higher media-multitasking associated with smaller gray matter volumes
When they compared the fMRI data with the media-multitasking data, the researchers found higher media-multitasking was associated with smaller gray matter volumes in the anterior cingulate cortex.
However, they also found a correlation between media-multitasking and extraversion in the Big 5 scores, leading them to wonder if this might be confounding the link between media-multitasking and gray matter volume.
But when they ran another analysis called a multiple regression that took into account the Big 5 as possible predictors of high media-multitasking, the results were the same. There appears to be a "unique association" between media-multitasking and gray-matter density in the anterior cingulate cortex that is independent of personality, conclude the authors.
Study found link - not cause and effect
However, the authors are keen to point out all they have established is a link - it would take another type of study to find out if media-multitasking causes changes in the brain or whether people with less dense gray matter are attracted to media-multitasking.
Scientists have shown brain structure can change with experience and under different conditions. Brain cells and pathways respond to changes in behaviors, emotions and environments, and "cortical re-mapping" can re-route brain functions to intact regions when damage occurs.
There are also studies that show training can increase gray-matter density. For example learning to juggle, or when taxi drivers learn the map of London in the UK. For trainee London cabbies to acquire what is termed "The Knowledge," they have to learn and locate 25,000 streets and 20,000 landmarks, as well as their intricate layout.