tap into real needs (e.g. combating the dangers of obesity)• present clear goals (e.g. realistic weight targets)• make it easy to do what is needed (e.g. prepare healthy meals)• give feedback about the progress made so far (e.g. compare your present weight with yourinitial and ideal weights)• provide clear visualizations of potential means or ends, so that users can easily imagine theeffect of their future actions (e.g. a computer-generated photo of how you would look afterlosing all that weight)• make use of social pressure (e.g. by pointing out the achievements of others)• provide timely triggers to stimulate their users to do something (e.g. alarms to remind you toexercise)

More generally, a persuasive system can be seen as an implementation of what has beencalled the extended will (J. Heath & Anderson, 2010). This is a generalization of the idea that weuse various information technologies as external memories, so as to “extend our mind” into theenvironment (Clark & Chalmers, 1998; Heylighen & Vidal, 2008). But mind encompasses morethan memory and information processing capability: it also includes the motivation, concentrationand determination needed to act effectively—i.e. what is conventionally called “will”. In ourpresent environment full of distractions and temptations, our willpower is heavily taxed. Therefore,in general we need external support if we want to make sure that we stick to our intentions (Allen,2001; J. Heath & Anderson, 2010).