A clinician is treating an adolescent with conduct disorder. The adolescent has been in foster care since his parents died many years ago, so there is limited information about his early behavior. The clinician has learned that recent research suggests there may be neuropsychological involvement when the onset of conduct disorder occurs at a young age, but not at an older age. The neurological tests required would be very expensive to conduct, so the researcher is unsure whether they should be added to the tests she is already using. In this case, the researcher is probably concerned with

a. the construct validity of the neurological test.
b. the face validity of the neurological test.
c. the concurrent evidence of validity for the neurological test.
d. the incremental validity of the neurological test.

d. the incremental validity of the neurological test.