Supplementary materials for the paper:
An investigation of the evolutionary origin of reciprocal communication using simulated autonomous agents.
Biological Cybernetics Journal, Vol. 101, No 3, pp 183-199, 2009.
Author: Elio Tuci
Table of Contents
Fitness curves of unsuccessful evolutionary runs
Table 1 - results of post-evalution tests
Movies of successful group g2
To download the movie of successful strategy group g2 right click here, to view it directly on the browser click on the picture below. Figure 2 refers to data recorded during the performance shown in the movie.
Why g3 and g4 fail?
Contrary to what observed in successful groups, group g3 is preferentially in a sound-state. The emission of sound is temporarily stopped by the perception of black ground. When located in E11, both agents stop emitting long enough for the group to switch from the sound-state to the no-sound-state while approaching the revolving door. Consequently, both agents push the revolving door on the correct arms. When located in E01 and in E10, the agent that experiences grey never stops emitting sound. The group remains in a sound-state, and both agents push the revolving door on the correct arms. When located in E00, the group fails since it lacks the conditions to switch from the sound-state to the no-sound-state. Group g4 behaves in a very similar way to what observed in successful groups. However, contrary to successful groups, agents of group g4 do not have any means to switch from sound-state to a no-sound-state states when located in E11. Therefore, anytime both agents experience black ground, the group is unsuccessful. Further data, obtained from tests P, confirmed that the only difference between successful and unsuccessful groups is a sound signalling failure that systematically stops unsuccessful groups from developping the appropriate pushing strategy when located in one specific environment. We recorded the categorisation outputs emitted by each agent of each selected group, in each environment during the approaching phase (i.e., from the beginning of the second phase of the task to the time of the agent's first collision with the revolving door), and we computed first, second (median), and third quartile for each data set. In Table 2, for each environment, the descriptive statistics refer to either data gathered in successful trials (see Table 2, columns S), if the group success rate turned out to be higher than 80% in that environment, or to data gathered in trials in which agents committed W1 error (see Table 2, columns W1), if the group W1 error rate turned out to be higher than 80% in that environment. As expected, in successful groups g1 and g2, for three quarter of the approaching phase in E01 and in E10, the categorisation outputs of both agents remain set to the signal upper bound, whereas, for three quarter of the approaching phase in E00 and in E11, the categorisation outputs of both agents remain set to the signal lower bound. This means, that agents of groups g1 and g2 are able to distinguish and correctly categorise E01 and E10 from E00 and in E11, by differentiating, during the approaching phase, the categorisation outputs associated to each type of environment. Contrary to what observed in groups g1 and g2, in unsuccessful groups g3 and g4, the statistics concerning the environments in which the groups fail mostly due to W1 error (i.e., E00 for g3, and E11 for g4, see Table 2) do not differ from the statistics concerning the environments that require different pushing strategy and in which the groups have a high success rate (i.e., E01 and E10 for both groups, see Table 2). This means that, for what concerns the categorisation output, agents of groups g3 and g4 mistake E00 and E11 respectively, for an Eanti type of environment. However, the causal relationships between categorisation output and pushing strategies in unsuccesful groups are identical to those illustrated for successful groups. Therefore, while approaching the revolving door in E00 for group g3, and in E11 for group g4, the agents keep the central light on their left since their categorisation outputs are errouneously set to the upper bound. Consequenlty, in these environments, the agents systematically end up collising with the current wrong arms of the revolving door. Given that further analyses of the behavioural strategies proved that agents of groups g3 and g3 vary their categorisation output in response to sound, it follows that the maladapted use of categorisation output mentioned above is caused by acoustic interactions that are not sufficient to unambigously and correctly classified all the environments.Table of Contents
Memory test (group g2)
Further post-evaluations tests on group g2 in which we deliberatly add/remove sound at given intervals while the agents are approaching the revolving door, show that the agents are extremely sensitive to these kind of variations. In particular, we run seventh times tests P each time changing the status of sound while the agents are navigating in the areas shown in Figure 3a. For example, during the 1st test P, we change the status of sound for the time it takes to the agents to traverse the corresponding area indicated as 1st zone in Figure 3a. For all the tests, the nature of the change is such that, for trials in E01 and in E10, the agents do not perceive sound even if one of them is emitting; for trials in E00 and in E11, the agents perceive sound even if none of them is emitting. The results clearly show that in all the tests, the disruptions make the percentage of success drop below 30% (see Figure 3b). The agents commit in all the tests mostly W1 error (see Figure 3c). That is, even a slight interference on sound far away from the revolving door (e.g., like in the 1st test, see Figure 3a 1st zone) makes the agents swap pushing strategy. That is, if sound is played while no agents is emitting (i.e., during trials in E00 and in E11), the agents often enter into a no-sound-state and they erroneously push the revolving door in a anticlockwise direction. If the agents are made deaf while one of them is emitting (i.e., during trials in E10 and in E01), the agents often enter into a sound-state and they erroneously push the revolving door in a clockwise direction. If the experimenter-induced perception of or deafness to sound appears when the agents are close to the revolving door (e.g., like in the 7th test, see Figure 3a 7th zone) than the frequency of W3 error increases. What happens is that the agents can not excert enough forces to completely rotate the revolving door. In this circumstance, W3 error is less frequent when the disruption concerns trials in E00 and E11 than when it concerns trials in E10 and E01. This analysis has been conducted also on successful group g1, and it produced very similar results. Thus, we conclude that both successful groups are very sensitive to even small interferences with the agents' signalling system. This suggests that the significance of signalling behaviour is not limited to the time during which the agents are on the coloured zones. That is, to bring fourth their successful strategy, the agents need a certain continuity in signalling behaviour during the time it takes them to move from the coloured zone up to the revolving door. In a way, sound and the absence of sound are two environmentally induced circumstances which remind the agents what to do while aproaching the revolving door.Table of Contents
Evolutionary graphs concerning g1
These graphs show the same phenomena described in in Section 4.1 An Evolutionary analysis of the paper. Also in run1, the distinctive different strategy with respect to signalling and setting the categorisation output that is associated to environment E00, and characterises generation 800 agents but not generation 650 agents, when it appeared it produced groups that on average were more adapted than those that did not showed any strategy differentiation (see Figure 4c). This strategy differentiation is determined by the emergence of mechanisms that regulate the sound and categorisation output in response to environmental stimuli.