Just one glass of wine may impair sense of control: Study

Drinking only one pint of beer or a large glass of wine is enough to significantly compromise a person's sense of agency -- the feeling of being in control of actions, according to a study.

The study, published in the journal Addiction Biology, is the first to test the effect of alcohol on sense of agency, an important aspect of human social behaviour which implies knowledge of the consequences of those actions.

Researchers from the University of Sussex in the UK focused on low doses of alcohol, typically consumed during social drinking, that do not produce a large impairment of behaviour.

Until now, research has mostly focused on the loss of inhibitory control produced by obvious drunkenness, characterised by impulsivity, aggression and risky behaviour.

"Our study presents a compelling case that even one pint of beer is enough to significantly compromise a person's sense of agency," Silvana De Pirro, lead author of the research paper, said.

"This has important implications for legal and social responsibility of drivers, and begs the question: are current alcohol limits for driving truly safe?" De Pirro said.

When physical stimuli -- such as sounds or lights -- follow voluntary actions, such as moving a finger or a hand, people judge actions as occurring later and stimuli as occurring earlier than in reality, hence 'binding' the two.

The neural mechanisms responsible for this phenomenon are thought to participate in creating the sense of agency.

In the experiments, subjects drank a cocktail containing doses of alcohol proportional to their body mass index (BMI) to produce blood alcohol concentrations within the legal limits for driving in England and Wales.

These doses of alcohol, corresponding to one or two pints of beer, produced tighter binding between voluntary actions and sensory stimuli.

This suggests that small amounts of alcohol might exaggerate the sense of agency, leading to overconfidence in one's driving ability and to inappropriate, potentially dangerous behaviour.

"It's important to note that in our experiments, all the participants stayed within the legal alcohol limit for driving in England, Wales, the US and Canada," said Professor Aldo Badiani, Director of the Sussex Addiction Research and Intervention Centre (SARIC).

"And yet we still saw an impairment in their feeling of being in control," said Badiani.