A study was performed involving phonological priming and tip-of-the-tongue states (TOTs) in which participants took either 200 mg of caffeine or placebo. Results show a clear positive priming effect produced for the caffeine group when primed with phonologically related words. When primed with unrelated words, the caffeine subgroup produced a significant increase in the number of TOTs. This contrasting effect provides evidence that the positive priming of caffeine was not a result of caffeine's well-known alertness effects. For placebo, a significant negative effect occurred with the related-word priming condition. The results support the novel hypothesis that the blocking of A, adenosine receptors by caffeine induces an increased short-term plasticity effect within the phonological retrieval system.

We report an investigation of phonological priming of a picture naming task in an anomic aphasic, PB, using caffeine as a pharmacological manipulation. We compare her results to controls on a similar paradigm testing the hypothesis that qualitative results in controls would carry over to the damaged brain demonstrating a "graceful degradation" in performance. When primed with words phonologically related to a target, PB made more word retrieval failures on caffeine as a function of related primes (controls make fewer) and fewer word retrieval failures as a function of unrelated primes (controls make more). The results thus supported the rejection of the hypothesis and we conclude that the use of the pharmacological manipulation provides a sensitive test for the graceful degradation of function.

Biological neural networks tend to exhibit a variety