Specifically, you can take up to two courses in the program without becoming a degree candidate. In that way, you may better judge how well this program meets your needs. After completing two courses, one must apply and be accepted into the program before further course credits can be given. But upon admission, one can attend part-time. If you are interested, you may certainly apply.
Many students do apply with background in other fields.
You may then be asked to take some additional coursework in psychology or research methods, or to demonstrate your competence by taking a special examination, before we grant full acceptance.