The Psychological mobility effect can be described as the individuals own perception on career structures and how they believe they can either transcend or be contained by them.

A boundaryless career involves transcends traditional boundaries found in firms and industries. This means that if someone has low psychological mobility, that is their belief is that one will find it difficult or impossible to move outside of the traditional career structures and boundaries, then they will be less likely to purse one.
Conversely if they have high social mobility, they believe that they can transcend the traditional boundaries of careers, then they will be far more likely to pursue this.