If they don't, he pulls the study, discards the data and makes changes at little cost of money or time. And he draws so many participants, it's easy to run a study over and over. In fact, now that his site is well-known, he reaches his goal of 50 participants per study within three hours. Of course, if an incentive is too good, some people may come back many times. If he omitted all but the first set of data from each computer, he found it made no difference to his results.
Technology glitches Web research poses other potential drawbacks besides repeat participation.
Although most types of psychology research will translate well to the Internet, some may not, says Krantz. For example, he's not yet convinced that he can control visual or auditory stimuli well enough over the Web to conduct a valid experiment in his main research area of sensation and perception. In particular, people on the Internet use different hardware and software and connect via systems with variable connection speeds. There's no way to ensure that everyone who participates in an experiment will receive exactly the same stimuli in terms of sound, color or timing, says Krantz. But he believes the technology will eventually become sophisticated enough to solve many of the problems.