You can do psychology, but you won't be able to do MATH1005.
One of the compulsory units you will have to do in a Bachelor of Economics is ECMT1010, and it is prohibited for anyone to do both ECMT1010 and MATH1005 due to the overlap of content. You might be able to get an exception to study MATH1005 if you really wanted to, but either way, you won't be able to do both. And I'd imagine the academic advisers would recommend you do ECMT1010 anyway.