This effect was identified by Reicher in 1969. An example of an experiment which demonstrates this is to present a test subject with a mask (something to block a stimulus), then a priming word, then a letter which corresponds to a letter in the priming word, and is in the same location, then another mask so that the visual processing of the stiluli cannot be continued. The experiment would run something like this:

1) The mask is presented for around 500 milliseconds eg -> "####"

2) The priming word is presented for around 20ms eg -> "WORK"

3) The target letter is presented for 50ms eg -> "- - - K"

4) The mask is presented again for 500ms - eg -> "####"

The priming word is flashed up on a screen so quickly that the test subject does not consciously preceive it. They barely have time to process the target letter consciously either. When, in the above example, a subject is asked whether the target letter is a “K” or a “D”, they cannot work it out from the “WOR” part of the prime, since either letter forms a word. The subjects report the letter “K”, the correct letter, significantly more often than the incorrect letter. This involves the idea of the regularity effect strengthening the neural connections involved in the letter recognition (this would be in accordance with Hebbian learning). The word superiority effect shows that people are quicker to recognise letters when they are presented in words than when they are presented alone. This effect can be explained by lingering excitation in Rumelhart and McClelland's interactive activation model of word recognition.