Modeling Hydra Behavior Using Methods Founded in Behavior-Based Robotics

42 Chapter 7. Results and discussiona random walk [66]. Jennings used the results from Wagner’s experiments in his detaileddescription of spontaneous activities in Hydra [28].To investigate the spontaneous movement patterns of the modeled Hydra, simulationsof the animal in the absence of any external stimulus during three days (72 hours) werecarried out. The foot position, (x f , y f ), of the simulated Hydra was recorded during thistime. Evident from the implementation details of LPs, as stated in Section 6.1.1, the resultsagrees with Wagner’s study in the sense that Hydra moves about in a random walk.Additional test data would allow for an expansion of this experiment, as is discussed inChapter 8. In the modeled Hydra, all locomotion steps are equally large, as discussed inSection 6.1.1. This differs from Wagner’s observations, in which the Hydra shows locomotionsteps of varying lengths. This limitation of the modeled Hydra is due to the simplificationsmade in the representation of the animal’s body, and a possible improvementis discussed in Chapter 8. The result from one realization of this simulation experiment isshown in Fig. 7.11.Figure 7.11: Position of Hydra during three days of spontaneous activity.7.2.2 Experiment B: Effect of starvation on contraction frequencyIn [46], Passano and McCullough studied the effect of starvation on the contraction frequencyof Hydra. The average contraction rate of animals fed daily, as well as every third