Informed consent and users' attitudes to logging in large scale trials.

The HCI community has begun to use 'app store'-style software repositories as a distribution channel for research applications. A number of ethical challenges present themselves in this setting, not least that of gaining informed consent from potential participants before logging data on their use of the software. We note that standard 'terms and conditions' pages have proved unsuccessful in communicating relevant information to users, and explore further means of conveying researchers' intent and allowing opt-out mechanisms. We test the hypothesis that revealing collected information to users will affect their level of concern at being recorded and find that users are more concerned when presented with a personalised representation of recorded data, and consequently stop using the application sooner. Also described is a means of allowing between-groups experiments in such mass participation trials.