if you are interested in the primary literature there are several papers from Jennifer Mather that might interest you.
Personalities of octopus
JA Mather, RC Anderson - Journal of Comparative Psychology, 1993
Early Temperamental Traits in an Octopus (Octopus bimaculoides). Journal of Comparative Psychology 2001. Vol. 115, No. 4, 351-364
David L. Sinn and Nancy A. Penin, Jennifer A. Mather Roland C. Anderson