The human mind tends to focus more on the vertical dimension as opposed to the horizontal one. In the first experiment, the curved glass takes away the perception of the vertical dimension giving the illusion that it may contain less wine as compared to the straight-sided wine glass. In the second experiment, participants poured more in the wider wine glass since the horizontal dimension is overlooked and the vertical dimension gives an illusion of less height due to the wider width. The slanted holding position of the glass when pouring out wine automatically takes away focus on the vertical hence the tendency to pour more as opposed to when the glass is standing tall on a flat surface such as the table.
The colour of the glass also affects quantity when it comes to wine consumption. The contrast created between the wine and the wine glass brings about a sense of quantity. Red wine contrasts with a clear wine glass compared to white wine. While pouring white wine into a clear glass gives the illusion of the two colours echoing each other, red wine appears to give more of a red alert signal, with every extra once of wine you pour creating more contrast. As such, participants were found to consume 9% more white wine as opposed to red when using clear coloured wine glasses of similar shape and size.