Ms. McKellar was 13 when "The Wonder Years" started in 1988 and when it ended five years later, she took a respite from acting to attend U.C.L.A. She expected that she would resume acting when she graduated, and she expected that she would major in film. In her freshman year, though, she found that she missed the structured logic that she had enjoyed in high school math, and she started taking math classes at U.C.L.A. "I felt my brain was getting mushy," she said. To her surprise, she excelled. Later, she was surprised by her surprise, because she had done well in math classes from elementary school through high school. But she had never considered studying math or science in college. "It wasn't like I thought about it and thought, 'No, I can't do that,' " she recalled. "It just never occurred to me."