In 2013, BBC News Magazine writer Tom de Castella discovered that pedestrian crossings up and down the UK were hotbeds of placebo buttons. A crossing in central London had programmed intervals for red and green lights, for example. Pushing the button would only impact the length of these intervals between midnight and 7am. In several other cities during busy periods, the crossings were programmed to alternate their signals at a specific rate. The buttons did nothing, but a “wait” light would still come on when they were pressed and, yes, people still pressed them presumably believing that their actions were having an effect.

Certain psychologists would argue that the buttons were indeed having an effect – just not on the traffic lights themselves. Instead the effect is in the commuter’s minds.

To understand this you have to go back to the early 1970s. At that time, psychologist Ellen Langer, now a professor at Harvard, was a graduate student at Yale. During a five card draw game of poker she dealt one set of cards in a haphazard order.

“Everybody,” she says, “got crazy. The cards somehow belonged to the other person even though you couldn’t see any of them.” Langer decided to find out more about the way people regulated the playing of such games. She went to a casino where, at the slot machines, she found gamblers with elaborate ways of pulling the lever. At another time a “highly rational” fellow student tried to explain to her why tossing a pair of dice could be done in a certain way to affect the numbers which came up. “People believed that all of these behaviours were going to increase the probability of their winning,” she comments.

Naturally they were wrong and for many people a simple objective proof of the matter would have been enough. But not for Langer. The strength of the gamblers’ convictions was, to her, not trivial.

‘Desirable state’

She wrote a paper in 1975 that made her very famous. In it she described the significance of these beliefs and coined a term for the effect that they had on people. Langer called it the “illusion of control”. Langer demonstrated this phenomenon experimentally by asking subjects to play a lottery. Some participants were able to choose their tickets and some of those tickets had symbols on them which were more or less familiar to them. The type of ticket had no effect whatsoever on their chance of winning, but they appeared to believe this was the case. Those who had chosen tickets with recognisable symbols were much less willing to part with them in an exchange than those who hadn’t.

But instead of framing this as an irrational delusion, Langer described the effect as a positive thing. “Feeling you have control over your world is a desirable state,” she explains. When it comes to those deceptive traffic light buttons, Langer says there could be a whole host of reasons why the placebo effect might be counted as a good thing. “Doing something is better than doing nothing, so people believe,” she says. “And when you go to press the button your attention is on the activity at hand. If I’m just standing at the corner I may not even see the light change, or I might only catch the last part of the change, in which case I could put myself in danger.”