Although it is obvious that people exerting full effort on a test score higher than people making less effort, it is not obvious to what degree poor effort affects neuropsychological test scores. Nor is it self-evident how well scores on an effort test based on memory predict scores on non-memory tests. In this study, effort was measured in 1307 consecutive outpatients using the Word Memory Test (WMT). The mean WMT effort scores were divided into six ranges, from satisfactory (91% to 100% correct) to very low (50% correct or less). The tables show the mean scores on many commonly used neuropsychological tests for each range of effort on the WMT. As effort decreases, scores on most tests decrease significantly and systematically. In this sample, the variable of effort had more impact on test scores than severe traumatic brain injury.