Gerard Gormley, for The Conversation:

Left-right discrimination is a complex neuro-psychological process involving several higher neurological functions such as the ability to integrate sensory and visual information, language function and memory. For some it is second nature but for others a considerable challenge. You can take a test here to see how well you do.

One further problem facing the health profession is that when a doctor or nurse faces a patient, their right-side is on the patient’s left-side. So correctly distinguishing right from left in a patient also involves the visuo-spatial function of mentally rotating images.

My technique: I can catch my middle finger’s metacarpophalangeal joint on my right hand — only my right hand. I’ve been doing it since I was a kid. If you say “right” or “left,” watch my hand flick. That’s how I know which side is which.