Rats distinguish between absence of events and lack of evidence in contingency learning
Animal Cognition (2012) - Comment
pubmed: 22744612  doi: 10.1007/s10071-012-0524-8  issn: 1435-9456  issn: 1435-9448 

Michael R. Waldmann, Martina Schmid, Jared Wong, Aaron P. Blaisdell