Extras

Eye-catching studies that didn't make the final cut:

Australian psychologists ask whether it's time for a professional oath in psychology.

Jealousy.

Sherlock Holmes and expertise: "Although nearly 120-years-old, Conan Doyle's books show remarkable illustrations of expert behaviour, including the coverage of themes that have mostly been overlooked by current research."

Why do humans kill?

An automatic face-recognition system with 100 per cent accuracy.