Implementation of Psychology in Aplysia
"Dynamical basis of intentions and expectations in a simple neuronal network" (PNAS subscription required, there's a free abstract):
[R]ecent indirect evidence suggests that intentions and expectations may arise in behavior-generating networks themselves even in primates [...]. In that case, interestingly, the intentions and expectations inferred from behavioral observations are not always identical to the intentions and expectations that are consciously accessible [...]. In this study we have demonstrated how such intentions and expectations arise automatically in the feeding network of Aplysia.
The "intentions and expectations" found are basically this: if you repeatedly present an A-stimulus to one of Aplysia's central pattern generators, and then switch to a B-stimulus, the pattern generator will respond as if it received another A-stimulus. Only after several B-stimuli will it switch to responses adequate for B. In this sense the animal expects to receive further A-stimuli, and intends to produce further A-behaviour. In a similar, slightly strechted, sense one could say that the animal believes to be in an A-environment (which is an environment containing seaweed). This belief is a certain state of the synapse linking Aplysia's neurons B20 and B8.