The lab’s first Javascript experiment has been online for about 3 weeks now, and has amassed close to 200 participants. It’s been a great experience discovering that the benefits of online testing (60+ participants a week, many of them run while I’m asleep!) easily outweight the costs (the time expended learning Javascript and coding all the fiddly bits, particularly the informed consent procedures and performance-appropriate feedback).

On top of the study completion data that’s obvious from the 7 KB csv file that each happily-debriefed participant leaves behind, the Google Analytics code embedded in each page of the experiment provides further opportunity to explore participation data.


As the experiment structure is entirely linear, it’s possible to track the loss of participants from each page to the next.

Study Attrition

The major point of attrition is between the Participant Information Page and the Consent Form – not surprising given quite how text-heavy the first page was, and how ‘scary’ headings like “Are there any potential risks to taking part?” make the study sound. The content of that first page is entirely driven by the Informed Consent requirements of the University of St Andrews, but the huge attrition rate here has prompted a bit of a redesign in the next follow-up study.


New Visits by Browser

Other information useful for the design of future studies has been the browser data. As might be expected, Firefox and its relatives are the dominant browsers, with Chrome a distant second and Internet Explorer lagging far behind. Implementing fancy HTML5 code that won’t work in Firefox is therefore a bad idea. On top of that, despite how tablet- and phone-friendly the experiment was, very few people used this sort of device to complete the study – it’s probably a waste of time optimising the site specifically for devices like iPads.

Study Completions by Browser
Study Completions by Browser

Curiously enough, when the data for study completions are explored by browser, the three major platforms start to level up. Chrome, Firefox and IE all yield similar completion statistics, suggesting that IE browsers are far more likely to follow through and complete the study once they visit the site. I’m speculating here, but I suspect that this has something to do with a) this being a memory study and b) IE being used by an older demographic of internet user who may be interested in how they perform. Of the three major browsers, Firefox users have the worst completion rate.


Another consideration with word-based experiments is the location of participants. This could impact on the choice of words used in future studies (American or UK spellings) and could be considered important by those who are keen to exclude those who don’t speak English as their first language. Finer grained information about participants’ first languages is something we got from participant self-reports in the demographic questionnaire, but the table of new visits and study completions is still rather interesting.

New Visits and Study Completions by Country

Once again, there are few surprises here, with the US dominating the new visits list, though one new visit from a UK- or India-based browser is more likely to lead to a study completion. A solid argument for using North American spellings and words could also be made from these data.

Source of Traffic

The most important thing to do to make potential participants aware of an online psychology study is to advertise it. But where?

Study Completions by Source

While getting the study listed on stumbleupon was a real coup, it didn’t lead to very many study completions (a measly 2.5%). That’s not surprising – the study doesn’t capture the attention from page 1 and doesn’t have much in the way of internet meme-factor. That is, of course, something that we should be rectifying in future studies if we want them to go viral, but it’s tough to do within the rigid constraints of the informed consent pages that must precede the study itself.

The most fruitful source of participants was the Psychological Research on the Net page. It was much more successful at attracting visits and study completions than facebook, the best of the social networks, and the other online experiment listing sites on which we advertised the study ( and What’s more, there has been a sustained stream of visitors from the page that hasn’t tailed off as the study has been displaced from the top of the Recently Added Studies list.

These statistics, surprised me more than any other.  I assumed that social networking, not a dedicated experiment listing page, would be how people would find the study. But in retrospect, it all makes sense. There is clearly a large number of people out there who want to do online psychology studies, and what better way to find them than to use a directory that lists hundreds of them.  If there’s one place you should advertise your online studies, it’s

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