A food scientist explains why Doritos are the perfect snack

Doritos are one of the most successful snack foods ever, with a market-leading $1.5 billion in annual sales in the US.

What makes them so good? Food scientist Steven Witherly explained "the perfect snack food" at length in his book, "Why Humans Like Junk Food."

We break down the highlights - with mouthwatering glamour shots - below.