In most online citizen science projects, a large proportion of participants contribute in small quantities. To investigate how low contributors differ from committed volunteers, we distributed a survey to members of the Old Weather project, followed by interviews with respondents selected according to a range of contribution levels. The studies reveal a complex relationship between motivations and contribution. Whilst high contributors were deeply engaged by social or competitive features, low contributors described a solitary experience of 'dabbling' in projects for short periods. Since the majority of participants exhibit this small-scale contribution pattern, there is great potential value in designing interfaces to tempt lone workers to complete 'just another page', or to lure early drop-outs back into participation. This includes breaking the work into components which can be tackled without a major commitment of time and effort, and providing feedback on the quality and value of these contributions.

Online display advertising is predicted to make $29.53 billion this year. Advertisers believe targeted and personalized ads to be more effective, but many users are concerned about their privacy. We conducted a study where 30 participants completed a simulated holiday booking task; each page showing ads with different degrees of personalization. Participants fixated twice as long when ads contained their photo. Participants reported being more likely to notice ads with their photo, holiday destination, and name, but also increasing levels of discomfort with increasing personalization. We conclude that greater personalization in ad content may achieve higher levels of attention, but that the most personalized ads are also the least acceptable. The noticeability benefit in using someone's photo to make them look at an ad may be offset by the privacy cost. As more personal data becomes available to advertisers, it becomes important that these trade-offs are considered.