The mind and body are usually thought of as separate entities but they are, in fact, intimately linked. The mind controls the body, of course, but the relationship is reciprocal – the body also influences the mind in mysterious ways, such that our thoughts and emotions are grounded in our bodily sensations and movements.
We now know, for example, that the sense of touch can influence our social judgements and decisions; that ambient temperature affects how we perceive relationships with others; and that movements can affect the rate at which memories are recalled, as well as the emotional content of the memories. A team of psychologists from Erasmus University in Rotterdam now reports that body posture can unconsciously influence our estimates of quantities.
According to the mental number line theory, we think of numbers along a horizontal line with small numbers on the left and larger ones to the right. Rather than being specific to certain cultures, this seems to occur universally and may be due to the way in which the brain represents numbers. With this in mind, Anita Eerland and her colleagues hypothesized that secretly making people lean to the left or right would affect their estimations of quantities.
They recruited a total of 91 undergraduates and asked them 39 questions that involved making estimations of a wide variety of quantities. In the first experiment, 33 participants were asked to estimate quantities such as the height of buildings, the population of cities and the alcohol content of alcoholic drinks. In the second, 58 others were asked to estimate, for example, how many number one hits Michael Jackson had in the Netherlands, or how many grandchildren Queen Beatrix has, on a scale of 1 to 10.
The participants stood on a Wii balance board while answering the questions and were told that they had to adjust their posture to remain upright, using a crosshair on a computer screen in front of them. Actually, the researchers used the balance board to surreptitiously manipulate their posture, so that they leaned slightly to the left, slightly to the right, or upright. For each experiment, the participants were split into six groups, which differed only in the order in which the questions were presented and the postures were altered.
Afterwards, the participants completed a questionnaire indicating if they knew any of the answers. Although some claimed to know the answers to some of the questions, they did not answer those questions correctly, confirming that all their answers were indeed estimates. Nor were any of them aware that their posture had been manipulated during the experiment.
As predicted, all the participants in both experiments gave smaller estimates when leaning to the left. In the first experiment, for example, participants who were leaning slightly to the left estimated the Eiffel Tower to be 12 meters shorter, on average, than those leaning slightly to the right.