Influence of color on number perseveration in a serial addition task

The present study examined the influence of coloring the repeated number in a serial addition task that elicits perseveration in normal subjects. 110 undergraduates were administered the original, black-and-white version of the task, 112 other undergraduates the new, colored version. The task required adding the following numbers: 1000 + 40 + 1000 + 30 + 1000 + 20 + 1000 + 10. We predicted that, in the colored version, the enhanced saliency of the repeated number 1000 would reduce the incidence of perseverative errors. Results with the black-and-white version replicated our 1994 findings, i.e., the majority of subjects produced the perseverative response 5000 rather than the correct answer of 4100. Contrary to our expectation, color did not improve performance but rather increased both perseverative and nonperseverative errors. We speculate that the enhanced saliency of the 4 repeated 4-digit terms may have further distracted subjects from discovering the critical lure, namely, the repetitive digit changes in the partial sums at irrelevant positions, i.e., in the thousands and tens but never in the hundreds.