Scientists do experiments with all sorts: semiconductor lasers, low temperature helium, … babies. There is a paper in last week’s Science by Gweon and Schulz on reasoning in (16-month old) babies. Scientists can reason, at least I hope I can. If my mobile is inert, I check the battery isn’t flat by plugging it in and charging it. I do this because this the common cause of my phone going into inert-brick mode. I can tell you this and so demonstrate my reasoning power to you because I can type. Babies cannot type, so how can you find out if they can reason or not?

An answer is the in the paper (sadly behind a paywall, sorry). The answer is to do an experiment in which you play a trick on a baby (or 83 babies in their case). A bit mean, but only a little bit. The scientists took a green toy with a button on top. They rigged it so that when they pressed the button the toy made a sound, but not when the baby did the same thing.

They then pressed the button to show the baby it made a noise and then either handed either it, or a different and yellow toy to the baby. Like the green toy this yellow toy had a button but was deliberately broken. In each case there was a red toy placed near the baby.

So in each case the baby presses the button but there is no sound. What does the baby do next?

There are two scientific hypotheses available to the baby: 1) The toy has broken and no longer makes a sound. 2) The toy works but the baby is pressing the button in the wrong way. The first point is that if the baby goes for hypothesis 1) they should try another toy: the red toy deliberately put near them. But if they go for 2) they should pass the toy to their parent to get them to press the button the right way.

The second point is that 1) is less likely if the baby is handed the green toy that made a noise just before it was handed to them, than if they are handed a red toy that they did not see making a noise. A rational scientist would go for 2) if handed the green toy while 1) and 2) are both reasonable if they are handed the yellow toy.

Gweon and Shulz found just this behaviour with babies. We are all born scientists, it must be later cultural influences that make some of us go and become lawyers, etc.