The Graduate Record Examination is a standardised test that many undergraduates take as part of the application process to a postgraduate course in the US. It tests quantitative numerical, verbal and writing skills. Data on average scores, grouped by the field of study being applied for, is available online.
The further towards the top-right-hand corner a subject is, the smarter the applicants for that subject. Notice that physics, religion and foreign language majors have similar verbal scores, but the physicists have far greater quantitative scores. Of the three types of education, elementary (primary), secondary and higher, secondary school teachers have the highest scores of all.
The top of the quantitative scale is dominated by scientists, and is a little crowded, so an extract of the graph is below.
Now I don’t want to boast, but click to enlarge and look where Physicsts appear …