This article applies to:
Experiment Author: Adapted from STEP and used with permission of Brian MacWhinney
This experiment investigates the phenomenon whereby letters in words are recognized more quickly and readily than letters in irrelevant contexts (in a non-pronounceable string of nonsense letters, for instance).
In this experiment four letters appear on screen for 300 milliseconds and are then masked. One letter appears above the mask and another below. One of the two new letters matches one of the four letters that previously appeared. If the top letter matches, press the "t" key, if the bottom letter matches, press the "b" key. There are 45 trials in this experiment.
Rumelhart, D.E., & McClelland, J.L. (1982). An interactive activation model of context effects in letter perception: Part 2. The contextual enhancement effect and some tests and extensions of the model. Psychological Review, 89, 60-94.
Cited Experiment Abstract
The interactive activation model of context effects in letter perception is reviewed, elaborated, and tested. According to the model context aids the perception of target letters as they are processed in the perceptual system. The implication that the duration and timing of the context in which a letter occurs should greatly influence the perceptibility of the target is confirmed by a series of experiments demonstrating that early or enhanced presentations of word and pronounceable-pseudoword contexts greatly increase the perceptibility of target letters. Also, according to the model, letters in strings that share several letters with words should be equally perceptible whether they are orthographically regular and pronounceable (SLET) or irregular (SLNT) and should be much more perceptible than letters in contexts that share few letters with any word (XLQJ). This prediction is tested and confirmed. The basic results of all the experiments are accounted for, with some modification of parameters, although there are some discrepancies in detail. Several recent findings that seem to challenge the model are considered and a number of extensions are proposed.
Works Cited by the Experiment
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STEP: Facilitation in Recognizing Pairs of Words 
STEP: The Organization and Activation of Othographic Knowledge in Reading Aloud 
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