If an elastic band is first stretched and then subjected to heating, it will shrink rather than expand.  This effect was first observed by John Gough in 1802, and was investigated further by Joule in the 1850s, when it then became known as the Gough–Joule effect.
<br />Examples in Literature:
* Popular Science magazine, January 1972:  "A stretched piece of rubber contracts when heated.  In doing so, it exerts a measurable increase in its pull.  This surprising property of rubber was first observed by James Prescott Joule about a hundred years ago and is known as the Joule effect."
* Rubber as an Engineering Material (book), by Khairi Nagdi:  "The Joule effect is a phenomenon of practical importance that machine designers must consider.  The simplest way of demonstrating this effect is to suspend a weight on a rubber band sufficient to elongate it by at least 50%.  When an infrared lamp warms up the stretched rubber band, it does not elongate because of thermal expansion, as may be expected, but it retracts and lifts the weight."