could indeed reveal patterns of contagion. However, some were more
likely to catch the running bug than others. Over a five-year period,
the behaviour of less active runners tended to influence more active
runners, but not the other way around. This implies that keen runners
don’t want to be outdone by their less energetic friends.
Behavioural nudges like changes in weather are a useful tool for
studying contagion, but they do have limits. A rainy day might alter
someone’s running patterns, but it’s unlikely to affect other, more
fundamental behaviours like their marital choices or political views.
Dean Eckles points out there can be a big gap between what is easily
changed and what we ideally want to study. ‘A lot of the behaviours
we care the most about are not so easy to nudge people to do.’
I 2008 , Californians voted to ban same-sex marriage.
The result came as a shock to those who’d campaigned for marriage
equality, especially as pre-vote polls had appeared to be in their
favour. Explanations and excuses soon began to emerge. Dave
Fleischer, director of the Los Angeles LGBT Center, noticed that
several misconceptions about the result were becoming popular. One
was that the people who voted for the ban must have hated the LGBT
community. Fleischer dis agreed with this idea. ‘The dictionary defines
“hate” as extreme aversion or hostility,’ he wrote after the vote. ‘This
does not describe most who voted against us.’[52]
To find out why so many people were against same-sex marriage,
the LGBT Center spent the next few years conducting thousands of
face-to-face interviews. Canvassers used most of this time to listen to
voters, a method known as ‘deep canvassing’.[53] They encouraged
people to talk about their lives, and reflect on their own experiences
of prejudice. As they conducted these interviews, the LGBT Center
realised that deep canvassing wasn’t just providing information; it
appeared to be changing voters’ attitudes. If so, this would make it a
powerful canvassing method. But was it really as effective as it
seemed?
If people are rational, we might expect them to update their beliefs
when presented with new information. In scientific research this
approach is known as ‘Bayesian reasoning’. Named after eighteenth-