Ellen LangerI opened my talk at the Winchester Cafe Scientifique on 4 July with a description of an experiment conducted in the late 1970s by Ellen Langer of Harvard University, and her co-workers, Arthur Blank and Benzion Chanowitz of the City University, New York.

In a paper entitled ‘The Mindlessness of Ostensibly Thoughtful Action: The Role of Placebic Information in Interpersonal Interaction’, Langer and her colleagues described a beautifully simple experiment.

A Simple Favour

Would you do a favour and let someone go ahead of you when you were about to use a photocopier?

Queue for PhotocopierThe researchers asked 120 students if they could use a library photocopier first, just after the student had reached it.

The experimenter asked in three different ways:

  1. “May I use the Xerox machine?”
    Giving no reason
  2. “May I use the Xerox machine, because I have to make copies?”
    Giving no real reason
  3. “May I use the Xerox machine, because I’m in a rush?”
    Giving a reason

The Power of ‘because’

When the request was a small one – the experimenter had only five sheets to copy – 9 out of 15 (60%) of the students asked obliged without hearing a reason (Request number 1). With a reason (Request Number 3), 15 out of 16 (94%) agreed.

Here’s the surprise – with no real reason (Request number 2), 14 out of 15 (93%) were prepared to oblige. The reason is clearly not important; what was important was that there was a reason – the students heard the word ‘because’ and that was enough.

Higher stakes: Bigger ‘because’

Is ‘because’ sufficient in all cases? No. When the experimenter made a bigger request, to copy 20 pages, only 6 out of 25 students (24%) obliged with both of questions 1 and 2.

With a real reason, however, 10 out of 24 students (42%) were prepared to be generous. So to agree to a significant request, we need a significant reason.

Winchester Cafe Scientifique


It takes place on the first Monday of the month, at The Bridge Patisserie, 20 Bridge Street, Winchester. Tables start filling at around 7pm and it is usually standing room only by 7:30.
The Cafe resumes, after a summer break, on 3 October, with �What can mankind do to reduce global warming?

And here is the bonus… It is free to attend the cafe, with just a voluntary donation to meet the organiser’s costs.

Up to date information here.

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