That's men for you:'Assume a virtue if you have it not," the Prince of Denmark advises his mother as he rather tiresomely lectures her on the vexed topic of sleeping with his uncle.
Hamlet was talking about moral virtue but a similar principle has long been advanced in relation to the connection between our physical state and our mood.
If you carry yourself as though you are happy, angry, sad, etc then you are more likely to feel that way, the theory goes. The physical act summons up the emotion.
This is not simply pop psychology. The great psychologist William James, who died in 1910, and who is still quoted in everything from serious psychology texts to self-help books, suggested that our emotions actually come from physical activity and not the other way around.
He argued that " . . . we feel sorry because we cry, angry because we strike, afraid because we tremble . . ." You see something that "makes" you afraid. What happens next, James argues, is that you physically react to what you see. This physical reaction then leads to the emotion of fear.
If James is correct, then acting physically as if you are happy or sad should help to create that emotion in you.
There is a good deal of research to support this view. Some recent research even found that people's performance on tests of mathematics varied according to the posture they adopted, though the outcomes were different for men and women, of which more later.
In one study participants were asked to adopt the facial expressions linked with happiness, anger and sadness. They were not told why they were being asked to do this. When they were tested later, those who had assumed facial expressions consistent with happiness were happier than they had been at the start, those who had assumed an angry look were angrier than at the start and so on.
Interestingly, when asked to recall events from their lives, those who had practised looking angry were more likely to recall "angry" memories and so on.
All of this suggests that people who bounce around looking happy or people who mooch around looking sad may actually be contributing to their emotions by their physical demeanour. They don't slump because they feel sad, they feel sad because they slump.
And because of the way they carry themselves they are having different memories from those they would have if they carried themselves differently - and the memories then strengthen the emotion.
Like everything else, this theory can be taken to extremes. If, for instance, your house burns down and your wife runs away with her life coach, then no amount of posturing, I suspect, is going to spare you certain strong and unpleasant feelings.
Nevertheless, in everyday situations we can contribute much to our own sense of wellbeing by being aware of our physical selves.
What has this to do with maths? In a recent American study, 60 undergraduates were asked to assume either an upright posture or to slouch for three minutes. Afterwards, they were given a variety of tests including a test in maths. The men who sat up straight actually did better in maths than the men who slouched. Curiously, the women who sat up straight did worse in maths than the women who slouched.
The researchers speculated that the women who slouched may have felt more comfortable because slouching was consistent with their lower social status in a discriminatory world. Moreover, they suggested, sitting up and sticking their chests out might have made women feel self-conscious. I am not making this up - highly educated people get paid good money for this sort of thing and the results are in a very serious journal called Cognition and Emotion.
What all this means is that acting happy will help you to feel happy, especially if you're a man. And even more so, I guess, if you're a man doing arithmetic. So it looks like Hamlet was right after all - though the uncle would hardly agree.