Hello and welcome to more or less on the BBC World Service, with a programme that debunks

dubious data and clarifies confusing claims, and I'm Tim Halford.

January 1st is the day when we swear we'll work it, make it, do it, harder, better, faster,

stronger.

And roundabout now is the time that, if you're anything like me, your determination is

waning.

This year I've asked the universe to manifest a six pack for me.

I've been imagining sit-ups every night.

One day it might work.

Now some of you might say that my expectations are too high, a year little faith.

I spoke to the science writer David Robson, whose new book The Expectation Effect, is

all about the power of our expectations, positive and negative, to influence our behaviour

and even our physiology.

We started out by discussing placebo, not the band, the medical phenomenon.

We know that placebo's can do things like encourage the brain to produce its own painkillers,

they can change our blood pressure, they can reduce or increase inflammation.

I mean, what I find most fascinating though is that actually the placebo effect in clinical

trials seems to be getting more powerful.

And to give just one example, a study of 84 different trials for painkillers between the

1990s and 2013 found that at the start of those trials, the real painkillers outperformed

the placebo by about 27%.

By 2013, they only outperformed the placebo by 9%.

...