Answer
$\frac{1}{9}$
Work Step by Step
We know that $probability=\frac{\text{number of favorable outcomes}}{\text{number of all outcomes}}$
The number of all outcomes is $(4+3+2)(4+3+2-1)=9\cdot8=72$, because the first student can be anyone, the second can be anyone apart from the first one.
The number of good outcomes is $2\cdot4=8$ because the first person is a music major, the second is a psychology major.
Thus probability$=\frac{8}{72}=\frac{1}{9}$