Last month, Red Nose Day, a biennial charity extravaganza, managed to break its fundraising record despite the recession. But to what extent are charities recession-proof? Much depends on what motivates us to give, a subject that has been receiving a lot of attention from economists recently.

There are many possible motivations. One is pure altruism: we give to charity because we care about the well-being of others. A second infamous motivation for giving was advanced by the economist James Andreoni: the “warm glow”. Warm-glow givers donate money to charity because it makes them feel good.

There might not seem to be much difference between altruism and a warm glow, but there is: warm-glow givers don't think too much about whether the money they give will be effective. For example, research by the behavioural economist George Loewenstein, with Deborah Small, a marketing professor, and Paul Slovic, a psychologist, shows that people are typically more generous when presented with an identifiable victim – six-year-old Aisha in Niger – than with statistical evidence of hunger in Niger. While the altruist would want the evidence, the warm-glow giver just wants to feel the connection. A third motivation is social pressure: we give because we think that's what others expect of us.