The present studies were designed to determine whether color as an irrelevant dimension would affect task performance based on different levels of information processing (Posner and Mitchell, 1967), and to try to assess whether the factors of response competition, response facilitation, and distraction contributed to these effects. It was expected that color, being a visual dimension, would have an effect on task performance based on a comparison of visual codes, and might also affect task performance based on name code comparisons. Experiments 1 and 2 were designed to determine whether, if Ss were asked to make same-different judgments about either the names of two letters presented to them (Experiment 1) or the forms of the two letters (Experiment 2) , the varying of letter color on certain trials would affect task performance. According to Posner and Mitchell (1987), responses to physically identical pairs of letters are based on comparisons of visual codes of the letters; responses to name identical pairs are based on comparisons of name codes of the letters. The results indicated that irrelevant color affected fesponses based either on visual code comparisons or on name code comparisons. Since it seemed improbable that the matching of nominally coded information could be affected by visual factors Opener and Taylor, 1969), it was suggested that perhaps irrelevant color affected not the comparison of the nominal information, but rather, other aspects of task performance prededing and following this comparison
