Individuals with damage to the hippocampus show marked memory impairments for learning new declarative information in everyday life and on standardized memory tests. However, previous work by Duff and colleagues (2006) has shown that participants with hippocampal amnesia display robust learning for labels used to describe twelve abstract Chinese tangrams in a Barrier Task setting. The Barrier Task provides a collaborative and interactive learning environment consisting of a matching game in which the amnesia participants must, over 24 trials, describe the abstract tangrams to their significant partner (e.g., spouse or close friend) so that the partner may arrange them in the same order as the amnesia patient's cards. In this second phase of the research, we are studying the specific learning functions of the Hippocampus- namely pattern separation, a process in which distinct and unique representations are assigned to conceptually and/or perceptually similar stimuli. To do this we implemented a second Barrier Task where amnesia participants described twelve tangrams to a significant partner, however six of the tangrams were conceptually and perceptually dissimilar (e.g., camel, giraffe), while the other six were visually and conceptually similar (e.g., birds). The results show that hippocampal amnesia participants had marked difficulty in developing and using labels for the six similar tangrams, while displaying normal learning and label use for the six dissimilar tangrams. That is, for the six similar tangrams the amnesia participants required more effort (e.g., more words, turns) to place those cards than they did for the six dissimilar tangrams. These findings are consistent with current notions of the critical role of the hippocampus in pattern separation of similar stimuli.