Decisions are made everyday, yet we are not always aware of all factors that lead up to making a particular decision as we may be influenced by unconscious feelings or perceptions, and even though we may not notice it, our body also plays an important role in decision making.

Anita Eerland, a psychologist at Erasmus University Rotterdam in the Netherlands explains: “Decision making, like other cognitive processes, is an integration of multiple sources of information – memory, visual, imagery, and bodily information, like posture.”

In a new investigation, Eerland and her colleagues Rolf Zwaan and Tulio Guadalupe, discovered that secretly manipulating the tilt of the body influences the way individuals estimate quantities, such as numbers, percentages and sizes. The study will appear in the upcoming issue of Psychological Science, a journal published by the Association for Psychological Science.

When thinking about numbers, individuals tend to link smaller numbers to the left side of the brain and larger numbers to the right side. The team believed that leaning to one side or the other – even slightly – may shift individuals to estimate higher or lower. In order to test this theory, the team enrolled 33 undergraduates to participate in the investigation. Participants were told to stand on a Wii Balance Board that slightly manipulated their posture to lean towards the right or left or stay upright, while questions were presented on the screen for them to answer. The researchers told the participant that they were unlikely to know the answers and therefore would have to estimate. All participants were told to stand upright throughout the trials. On the screen below the question, a picture of the participant’s posture was shown to be upright even when it was not. All questions were answered one by one verbally.

The estimations in the initial trial were of different kinds of quantities, for example, the percentage of alcohol in whiskey, or the height of the Eiffel Tower. In the second trial, quantities were all of the same kind, for example – How many Number 1 hits did Michael Jackson have in the Netherlands? and How many grandchildren does Queen Beatrix of the Netherlands have? All the answers were between one and ten.

As anticipated, the researchers discovered that smaller estimations were given when participants leaned to the left than when leaning to the right or standing upright. They found do difference in estimations between upright postures and leaning right.

According to the team if you know the answer your body posture will not make you answer incorrectly. “You body posture may nudge your estimates in a particular direction,” explained Zwaan. “Posture doesn’t overwrite knowledge,” added Eerland.

Zwaan continues: “Still we should not mistake our cognitive processes as perfectly and consciously rational. Decision-making is not a pristine process. All sources of information creep into it, and we are just beginning to explore the role of the body in this.”

Written by: Grace Rattue