(screen grab from University of Essex demo)
UPDATE (September 14, 2017): the Uni Essex link is dead. Try this one from PsyToolkit instead.
Just found this online demo of a classic lexical decision experiment from the University of Essex here. Some images on the page don't seem to load, but the experiment runs just fine. It's a nice example of a simple psycholinguistics methodology that is commonly used in many experiments.
I'll let the good folks at Essex explain the task:
One of the key methods of investigating the processes involved in reading is the lexical decision task. Any model of reading needs to explain how a particular word can be selected from many similarly featured items, (known collectively as the neighbourhood). Neighbourhood size is a measure of the orthographic similarity between words (Coltheart et al., 1977). If a target word is orthographically similar to many words, then the target word is said to have a large neighbourhood (e.g the word sell has many neighbours such as tell, well, bell, yell and sill). A target word which is orthographically similar to few words is described as having a small neighbourhood (e.g. deny only has the neighbours defy and dent. In lexical decision tasks, Andrews (1989), found that words from large neighbourhoods elicit quicker responses than words from small neighbourhoods. This finding has been observed in a number of studies (e.g. Laxon et al., 1992: Scheerer, 1987). The facilitatory effect of neighbourhood size suggests that presentation of a target word results in activation of all the lexical entries which are similar to the target, and this local activation somehow speeds up target access. However, the precise nature of this facilitatory effect is a matter of continuing debate.
Now go enjoy the demo!
BTW, check out these other online psycholinguistics experiments here.