A '''behavior-shaping constraint''', also sometimes referred to as a forcing function, or [[poka-yoke]], is a technique used in [[error-tolerant design]] to prevent the user from making common [[error]]s or mistakes. One example is the reverse lockout on the transmission of a moving [[automobile]]. Another example from [[interaction design]], although not strictly a forcing function, is how software programs usually give a visual indication of what selection has been made by highlighting it with [[reverse video]] to aid in preventing [[description error]]s, where an intended action is performed on an object that isn't the one intended.
==External links==
*[http://www.diva-portal.org/diva/getDocument?urn_nbn_se_uu_diva-4275-1__fulltext.pdf A paper that includes the concept]
*[http://architectures.danlockton.co.uk Architectures of Control in Design, a site looking at constraints in the design of products, systems and environments]
