Anecdotal evidence has the power to change minds but facts are paramount

<span>Photograph: Simon Cooper/PA</span>
Photograph: Simon Cooper/PA

Welcoming good news is easy but it’s important to face up to bad news too, either to overcome it or quickly lower your expectations of life in line with it.

On the face of it, beneath an encouraging headline, there’s some crushingly bad news for those of us working on rigorous, evidence-heavy research in a recent study that investigates which information changes the minds of people on the role of international aid spending, the efficacy of which many are sceptical about.

The latter point in part explains why many countries are theoretically signed up to spending 0.7% of GDP on aid but most are doing no such thing. The chancellor’s autumn statement confirmed there was no imminent prospect of the UK returning to doing so.

The researchers conducted an experiment to evaluate the impact of telling people (specifically 6,000 Germans) that an aid programme worked, by measuring its effect on their belief in aid effectiveness. The good news is that this was positive, raising average support by more than 10%. But, crucially, they also examined whether that impact is greater if it is backed up by different kinds of evidence: a serious chart illustrating the results of a scientific evaluation of the programme or a simple anecdote of someone who benefited endorsing the programme. Which kind of evidence had the biggest effect in boosting public support? The words no social scientist wants to read are: “anecdotal evidence performs best”.

But all is not lost. After all, while some politicians may only worry about what convinces the public that they are right, researchers are also interested in what the truth is in the first place. And there evidence trumps anecdote every time.

• Torsten Bell is chief executive of the Resolution Foundation. Read more at