“Pain may also distract an individual by occupying part of that conscious limit and thus lowering their overall concentration or focus. This is not common in pain population.”
Oosterman JM, Derksen LC, van Wijck AJ, Weldhuijzen DS, and Kessels RP, Meory functions in chronic pain: examining contributions of attention and age to test performance. ClinJ of Pain. Sept 2010. (Epub ahead of print).