If you wander through New York's Museum of Modern Art, you'll eventually come across Painting Number 2 by Franz Kline, a set of thick, unruly black lines on a white canvas. Elsewhere, you will find one of Mark Rothko's many untitled works, consisting of various coloured rectangles. And in front of both paintings, you will inevitably find visitors saying, "A child could paint that."
To which Angelina Hawley-Dolan and Ellen Winner replied: "Could they?"