Shaping by successive approximations is an important animal training technique in which behavior is gradually adjusted in response to strategically timed reinforcements. We describe a computational model of this shaping process and its implementation on a mobile robot. Innate behaviors in our model are sequences of actions and enabling conditions, and shaping is a behavior editing process realized by multiple editing mechanisms. The model replicates some fundamental phenomena associated with instrumental learning in animals, and allows an RWI B21 robot to learn several distinct tasks derived from the same innate behavior. 1. Introduction Service dogs trained to assist a disabled person will respond to over 60 verbal commands to, for example, turn on lights, open a refrigerator door, or retrieve a dropped object [9]. Chicks can be taught to play a toy piano (peck out a key sequence until a reinforcement is received at the end of the tune) [6], and rats have been conditioned to perform c...

Instrumental (or operant) conditioning, a form of animal learning, is similar to reinforcement learning (Watkins, 1989) in that it allows an agent to adapt its actions to gain maximally from the environment while only being rewarded for correct performance. But animals learn much more complicated behaviors through instrumental conditioning than robots presently acquire through reinforcement learning. We describe a new computational model of the conditioning process that attempts to capture some of the aspects that are missing from simple reinforcement learning: conditioned reinforcers, shifting reinforcement contingencies, explicit action sequencing, and state space re nement. We apply our model to a task commonly used to study working memory in rats and monkeys: the DMTS (Delayed Match to Sample) task. Animals learn this task in stages. In simulation, our model also acquires the task in stages, in a similar manner. We have used the model to train an RWI B21 robot.

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The place fields of hippocampal cells in old animals sometimes change when an animal is removed from and then returned to an environment [ Barnes et al., 1997 ] . The ensemble correlation between two sequential visits to the same environment shows a strong bimodality for old animals (near 0, indicative of remapping, and greater than 0.7, indicative of a similar representation between experiences), but a strong unimodality for young animals (greater than 0.7, indicative of a similar representation between experiences). One explanation for this is the multi-map hypothesis in which multiple maps are encoded in the hippocampus: old animals may sometimes be returning to the wrong map. A theory proposed by Samsonovich and McNaughton (1997) suggests that the Barnes et al. experiment implies that the maps are pre-wired in the CA3 region of hippocampus. Here, we offer an alternative explanation in which orthogonalization properties in the dentate gyrus (DG) region of hippocampus interact with e...