Animals often show a keen intelligence and many species, from octopuses to crows, can perform problem-solving tasks. But humans are thought to go one step further. We can reflect on our own thoughts and we have knowledge about our knowledge. We can not only solve problems, but we know in advance if we can (or are likely to).

In technical terms, this ability is known as ‘metacognition’. It’s what students do when they predict how well they will do in an exam when they see the questions. It’s what builders do when they work out how long a job will take them to finish. But can animals do the same? Finding out is obviously difficult. No animal is going to tell