What positive quality did Charlie have that helped the doctors agree to the operation?

The answer to this question can be found in Progress Report 5. Dr. Strauss had the positive quality of "motivation".

Dr Strauss said I had something that was very good. He said I had a good motor-vation. I never even knowed I had that. I felt good when he said not everbody with an eye-Q of 68 had that thing like I had it. I dont know what it is or where I got it but he said Algernon had it too. Algernons motor-vation is the chees they put in his box. But it cant be only that because I dint have no chees this week.