Distractions too subtle to notice can actually affect our concentration more than obvious ones, according to a new U.S. study.
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SYDNEY: Subliminal distractions disturb concentration even more than obvious ones, according to U.S. researchers.
In a study published today in the U.S. journal Science, researchers found that subjects were more distracted by subtle movements in the background of computer screens - so subtle that they didn't even consiously register - than they were by more obvious movements.
In the study, the authors said that a body of evidence indicates that a 'sub-threshold' distraction - one that is too subtle for our conscious brains to notice - can nevertheless influence brain activity and behavioural performance.
Yoshiaki Tsushima from Boston University and his co-authors conducted a series of psychophysical and functional magnetic resonance imaging (fMRI) experiments to assess the level of distraction caused by various stimuli.
Volunteers were presented with a sequence of eight characters - two numbers and six letters - at the centre of a computer screen, and were asked to focus on, remember, and report the two numbers. At the same time, the researchers sought to distract the subjects with patterns of dots in the background. The patterns consisted of moving dots in either random or more obvious coherent patterns, none of which had any relation to the letters or numbers.
The authors found that the more subtle random dots - dubbed 'subliminal stimuli' - only barely activated the brain's 'distraction control centre', a region in the brain called the lateral prefrontal cortex (LPFC).
According to the study, the LPFC is best at controlling distractions when fully activated, and so more obvious distractions can actually be better controlled than subliminal ones.
"A weak task-irrelevant stimulus…that is below, but near, the perceptual threshold, more strongly activates the visual area…and more greatly disrupts task performance," said the authors.
"One would naturally assume that the degree of an invisible stimulus' influence is generally weaker than that of a visible stimulus."
However subliminal stimuli are now thought to impact concentration levels because they are not fully detected by the brain and therefore are not effectively blocked out.
The authors also believe that the results could reveal important interactions between the visual system and the brain's cognitive control centres. Task-irrelevant signals might be strong enough for the visual system to process but not strong enough for the LPFC to detect and control the signals.
"In this case, such signals may remain uninhibited…and disrupt task performance more than [obvious] signals."
