How people and animals learn about their environment is a major area of study within psychobiology. The objective of Dr. Palya's research is to contribute to the development of a model of behavior that would account for an organism's increase in adaptation to the environment with increasing experience (the "learning curve"), as well as accounting for a particular phenomenon observed in many experiments using fixed-interval schedules of reinforcement. In such experiments, performance of a specified action (or "response") is reinforced only when a specified constant interval of time has elapsed since the last occurrence of a reinforced response. Given practice with such a fixed-interval schedule, animals or people often learn to make few responses early in the interval and to respond at an increasing rate as the interval progresses, apparently in anticipation of reinforcement at the end of the interval. In order to test theoretical predictions about the distribution of responding within an interfood interval, Dr. Palya will carry out experiments using pigeons responding for food reinforcement. Dr. Palya will experimentally segment the interfood interval into ten different, explicitly signaled periods. An overt response will be required to present or remove each of the signals associated with consecutive portions of the interfood interval. Dr. Palya predicts that the initial portion (up to the midpoint) of the interval will be decreasingly aversive, while the later portion of the interval will be increasingly reinforcing. Dr. Palya's prediction is based on his extension of a widely used mathematical model of learning, the Rescorla-Wagner model, which predicts only the behavior that will occur the moment before food appears. If the extended model correctly predicts the learning of the distribution of responding throughout the inferfood interval, Dr. Palya's research will have contributed to the goal of developing a general theory of learning and behavior.
