how long is a undergraduate thesis

As part of their final year undergraduate degree examination for MA or BSC Psychology, students submit a dissertation based on an original research project supervised by academic staff in the department.
During 2006/07 it was agreed that all Psychology Undergraduate students would be required to submit an electronic copy of their dissertation to the Library to be stored in the Edinburgh Research Archive. This was agreed in order to enable the University to preserve its academic record.

References:

http://barretthonors.asu.edu/thesis/examples