Can a person be brilliant even though slow at resolving problems? Can a person be very intelligent, able to solve difficult problems if given enough time, yet really a slow thinker? Especially if nervous. Could such a slow thinking brilliant person get all the questions on an IQ test correct even though they were 20 minutes beyond the required end of the test?

Another way of putting this question is regarding the validity of time limits on IQ tests.  How have these been arrived at?  Have other (extended) time limits been tested?  Have such time limits yielded different (higher) scores?
There are many definitions of intelligence. I find the one given by David Wechsler (1944) useful in the context of this question:


  The ... capacity of the individual ... to deal effectively with his environment


Finding a solution quickly is sometimes necessary if you want to deal with your environment effectively. Not all problems will wait for you to solve them slowly. Which is why the concept of intelligence usually includes a time component and a person solving the same problem slower is considered less intelligent.

"Brilliance" is not a psychological concept.



Source:


Wechsler, D (1944). The measurement of adult intelligence. Baltimore: Williams &amp; Wilkins.