A useful starting point is to find background information in subject specific encyclopedias in Alverno's library. This will give you the vocabulary you need to expand your searching.
When using subject specific encyclopedias in Alverno's library first try looking up the name of your theorist in the index. The specific theory might be listed there as well. Here are some useful titles:
You can find many useful books, book chapters, and encyclopedia articles in electronic format by doing a search in the PsycBOOKS database. A link to it can be found on the library's Databases by Subject - Psychology & Social Work page.
Try searching in this database for "Piaget" AND "theory" or try looking for "Piaget" as an author.
Here is a direct link to PsycBOOKS.
Books can give you a good overview and some history on your topic. Use TOPCAT to find books on your topic. Try some of these searches:
Find journal articles on your theorist or theory by doing a search in PsycINFO or PsycARTICLES. Visit the library's Databases page and select Psychology & Social Work to find links to either database.
If you do an author search in either database using the name of your theorist for your search term, you will find articles written by your theorist.