Researchers and the public alike have waxed enthusiastic about citizen science projects, in which professional and amateur scientists collaborate on experiments. And why not? Interested laypeople can engage directly in science, and for scientists like me, the setup provides manpower to tackle otherwise infeasible tasks.

Until recently, prospective citizen astronomers or biologists have had their choice of projects, but few opportunities existed for amateurs interested in the human mind. Now the tide is turning. Here are three mind-related projects, currently enlisting new amateur investigators:

The Small World of Words. This brainchild of Gert Storms and Simon De Deyne of the University of Leuven in Belgium seeks to understand the relations among words. Citizen scientists see a series of words and are asked to name what other words come to mind.

Gathering this information helps researchers determine, for instance, how people's intuitive associations between words change over time. Two decades ago most people's first response to “climate” would be to think “weather.” Now around 40 percent say “change.” Associations also depend on culture: whereas Americans most commonly say “baseball” in response to “pitch,” the British say “football.” The lead scientists have built impressive visualization tools for exploring their preliminary results.

The Baby Laughter Project. Caspar Addyman of Birkbeck, University of London, hopes to discover when babies laugh and why. Parents can fill out a survey about their baby's laughter, and anyone can file a field report on any particular episode in which they saw a baby laugh. As Addyman explained in a recent interview, what babies find funny gives us insight into what they understand about the world around them.

VerbCorner. This is my own project, with the Computational Cognitive Science Group at the Massachusetts Institute of Technology. It aims to determine what words mean. You might think the problem is already solved: just look them up in a dictionary! Dictionaries simply define words in terms of other words, however, which themselves are defined in terms of other words, and so on without end.

At the Web site, both volunteers and researchers in my laboratory answer questions designed to elucidate specific aspects of word meaning. As with many citizen science projects, the tasks are gamelike, with badges and points to be earned and fanciful backstories for each series of tasks.

For more on citizen science, visit