Gill and O’May (2007) asked participants to pour the equivalent of their usual drink and tested their knowledge of unit allowances.
The results showed that 49% of participants did not know the recommended daily llowance.
In addition,the glass size appeared to have an effect on the amount of alcohol ispensed, with more alcohol being poured into large volume glasses compared to smaller glasses.
Men poured larger amounts of red wine than women, resulting in high unit levels of alcohol consumed per drinking session.
The study concluded that people visually calculate one unit of alcohol based on the size of the glass in which it is served; this is often an under estimate and does not consider the percentage of alcohol present in the drink. This evidence suggests that
individuals calculating how much alcohol they consume may underestimate the degree of risk they are exposed to.