Detection of repeated trigrams: evidence of all-or-none learning

Two experiments investigated trigram detection in a continuous recognition task. In Experiment 1 consonant trigrams were presented visually, one at a time, with occasional repetition of a trigram after an interval of 0, 2, 4, 8, or 16 other trigrams. Subjects were told to respond with a button press every time they saw a repeated trigram. If a subject responded to a repeated trigram, it was not repeated again. However, if a subject did not respond to a repeated trigram, it was repeated again at the same interval for up to 3 repetitions. For all intervals greater than 0, the probability of noticing a repeated trigram did not increase with the number of repetitions. In Experiment 2 meaningless shape trigrams were presented, and occasionally a trigram was repeated after an interval of 0, 1, or 2 trigrams. For both intervals greater than 0, the probability of noticing a repeated trigram did not increase with the number of repetitions. The results demonstrate that a repeated input does not necessarily leave a permanent trace in memory.