We studied changes to the pattern of speech errors as a function of selectively attending to one word in a sequence to learn how attention is implemented in language production. Three hypotheses were tested: (1) attention specifically inhibits the past, (2) attention enhances the activation of the present without affecting the past or the future, and (3) attention decreases priming of the future. In Experiment 1, using a model of sequential word production, we simulated the pattern of anticipatory and perseveratory errors on the attended words, and compared them to empirical error data. Our findings support a model in which attention only affects the present. Experiment 2 tested the prediction of this model regarding the error patterns on the word following the attended word. These results were also compatible with a transient enhancement in the activation of present that does not affect the production of the future words.