PsycINFO is the database to use for literature searches about psychology, psychiatry, behavioral science (including animal behavior), and mental health. The things you already know how to do probably include keyword searching and using FindIt to link to the full text of articles. Using the limits can make your search more precise.
To see the limits offered you have to scroll down the search page. PsycINFO offers many ways to limit the scope of your search: journal title, publication years, age groups, and population group are just a few. Methodology is a popular limit with undergraduate students; you can limit to types of studies like longitudinal, quantitative, or qualitative.