These use light waves to scan individual green beans, which are rejected by a puff of air if they show up as defective.

ECONOMIST: Espresso coffee

After several repetitions, the animals learned to blink after hearing the noise in anticipation of the puff of air, and they timed their blinks to avoid it.

ECONOMIST: Neuroscience (2)

The researchers played a sound and then, after a set period of time that varied between each group, blew a puff of air into the rats' eyes, making them blink.

ECONOMIST: Neuroscience (2)

Moreover, the rats that successfully completed the more difficult task, which involved a longer gap in time between the sound and the puff of air, had retained more new neurons than those assigned easier tasks, with shorter gaps.

ECONOMIST: Neuroscience (2)