The following is the text of the Headmaster’s address to the school in Assembly on Monday 21 June 2010

Imagine someone in authority asks you to do something really bad - something which conflicts strongly with your own personal conscience. Imagine, for instance, that someone in authority asks you, in the interests of scientific research, to administer a potentially lethal electric shock to someone else. Someone who has never done anything to you, by the way, or indeed to anyone else. What would you do? How would you react? How many of you would comply – how many would refuse?

Funnily enough, we have a pretty good idea, because this question is at the heart of a series of experiments conducted in 1961 by Stanley Milgram, a young assistant professorat YaleUniversity.

Milgram set up one of psychology’s grandest and most horrible hoaxes. He created a fake but realistic shock machine – and recruited hundreds of volunteers for an experiment to test how many, when ordered to do so, would deliver what they believed were lethal levels of electricity to an innocent third party - even to the point of death.

I’ll explain the experiment by pretending that you are the volunteer. You’ve volunteered because they are offering money for an hour of your time – simple as that. You don’t know any more – but this is at YaleUniversity, after all – what can possibly go wrong? Surely you won’t be asked to do anything unethical.

You arrive, and, along with another volunteer, you’re told by a scientist that you are going to participate in an experiment to test the effect of pain on our power of memory. [In fact the experiment is a hoax: the other two people involved know what’s going on – you’re the only one that doesn’t.]

Essentially, what happens is this. The supposed scientist (in fact an actor) tells you and the other volunteer (who is also an actor, in on the trick) that the experiment involves two roles: one of you will be a “teacher” and the other will be a “learner”. The experiment will involve memory tests: putting together “word pairs” from memory: lake, luck; hay, sun; tree, loon; laughter, child – and so on. Every time the “learner” gets an answer wrong, the “teacher” will give them an electric shock. Before the experiment starts, just so that you know what sort of pain is going to be involved, you are then given a shock – 15 volts feels like a tickle, but 45 volts feels like the hot fangs biting into your skin, causing you to flinch.

Having given you a taste of what is to come, the scientist then asks you to draw lots, to see who will do which role. Unbeknownst to you, the lots are rigged. The actor pretending to be a volunteer always ends up playing the role of the “learner” who supposedly gets administered with electric shocks, whilst you will be the “teacher”, the person administering the shocks. The “learner” is then taken to a cell where, in front of you, he is strapped to an electric chair, after which you, the “teacher”, go with the scientist into a different room. From this point on, all communication is via an intercom system.

You are then given a list of word pairs which you have to teach the learner. The process starts and, eventually, the “learner” gets one wrong. So you are asked to administer a shock to the learner. This continues, with the voltage increasing in 15-volt increments for each wrong answer.

Remember, you believe that for each wrong answer, the learner is receiving actual shocks. In fact what you are hearing through the intercom system are the sounds from a tape recorder which has been integrated with the electro-shock generator, playing pre-recorded sounds for each shock level. After a number of voltage level increases, the actor starts to bang on the wall that separated him from the subject. After several times banging on the wall and complaining about his heart condition, all responses by the learner cease.

It is a truly devilish scenario. Surely, you’re thinking to yourself, nobody would administer a shock they thought to be lethal – we’d all stop way short of that, rather than administer pain needlessly to an innocent third party – wouldn’t we ? Well, Milgram’s findings were as shocking as the experiment itself. I’ll tell you about them next week. Until then, try to imagine what percentage you think would administer lethal electric shocks just because someone in authority tells you to do so. Five pounds to the first pupil who emails me the right answer.