S. Nolfi et al. (Eds.): SAB 2006, LNAI 4095, pp. 703 – 712, 2006. © Springer-Verlag Berlin Heidelberg 2006

Integration of an Autonomous Artificial Agent in an Insect Society: Experimental Validation

Grégory Sempo1, Stéphanie Depickère², Jean-Marc Amé1, Claire Detrain1, José Halloy1, and Jean-Louis Deneubourg1

1 Unit of Social Ecology, CP231, Université Libre de Bruxelles Av. F. Roosevelt, 50, 1050 Bruxelles, Belgium

gsempo@ulb.ac.be ² INLASA, Entomologia médica

Rafael Zubieta N°1889 (Lado del Estado Mayor General) Miraflores Casilla M - 10019, La Paz – Bolivia

Abstract. In mixed societies of robots and cockroaches, several insect-like-robot (Insbot) and animals interact in order to perform collective decision-making. Many gregarious species are able to collectively select a resting site without any leadership. The key process is based on the modulation of the probability of leaving the shelter according to the total population under this shelter and its light intensity. It is important that cockroaches perceive the robot as a “congener”. This recognition is mainly based on a chemical blend. The aim of this study is to validate experimentally (1) the behavioral patterns expressed by the cockroaches in presence of shelters and of an Insbot, and (2) the important role played by the chemical blend on collective decision-makings.

1 Introduction

With the rapid development of biology and biotechnology comes the growing need for systems where intelligent artificial and living agents cooperate. Controlling these interactions is therefore becoming a key challenge. Designing such synergetic societies requires studying new forms of information processing, problem-solving as well as synergetic behaviors between living beings and machines. Animal societies will be one of the first biological systems where living agents and autonomous artifacts will cooperate to solve problems. The machine does not replace the animal but collaborates and bring new capabilities to the mixed society. On one hand, the artificial systems bring new types of sensors, actuators and communication possibilities to the living systems; on the other hand the animals bring their cognitive and biological capabilities to the artificial systems.

This study is a part of the Leurre project [1] [2] from which the main objective is to prove that it is possible to develop and control mixed-societies composed of insects (cockroaches) and small insect-like robots (the Insbots). Previous related works have studied interactions between robots and different animal species such as rats [3], or dogs [4]. As regards gregarious species, one may mention the use of smart collars to

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hopefully control the herding behavior of cattle [5] or the Robot Sheepdog [6] to control a flock of ducks by moving them safely to a pre-determined position.

The challenge of the Leurre project [2] consists in the development of a mixed society where several robots and several animals are able to interact in order to perform collective decision-making. One example of such collective decision is shelter selection by groups of cockroaches [7] [8]. To reach this objective, it means:

1. to build of robots able to interact with animals; 2. that the artificial agents will be able to respond to the signals emitted by the

animals and to produce signals able to induce behavioral responses of the animals;

3. that the interactions designed for the artificial agents or used by natural agents, are of the type mutual inhibition, mutual activation and competition for limited resources [9].

Then, our first goal was to obtain social interaction between an artificial and an animal agent. Indeed, we will lure animals in such a way that robots are socially integrated in the animal society, so that they are considered by animals “as one of them”. This means that robot and animals influence each other, that they both contribute to the collective decision of the mixed society. Groups of cockroaches exhibit such collective decision-making: e.g. when several identical shelters are present, the group chooses only one of them. Many experiments have been performed with different species [7] [8]. The large American species, Periplaneta americana is our reference species to test mixed societies. The classical example of collective decision-making is when all group members choose the same solution among identical alternatives. This decision is collegial without any leadership or anthropomorphic procedure such as voting.

Contrary to the traditional lures that are elaborated following qualitative observations of the animal, the development of as well the hardware and the behaviour/software of our robot results from quantitative studies of the individual and collective behaviors of the cockroach. At the individual level, behavioral sciences have shown that animals’ interactions could be rather simple signals and that it is possible to interact with animals not only by mimicking their whole behaviors but also by making specifically designed artifacts. In this respect, the challenge was to determine the pertinent communication channels needed to integrate the robot within the animal group and to validate the repeatability of results in real experiments with animals.

Concerning cockroaches, several studies have shown that recognition between individuals is based on the chemical compounds present on their body. Consequently, the robot was wearing a paper dress containing the cuticular extract of cockroaches [10]. At a collective level, the cockroach P. americana is a gregarious insect that forms large cluster of individuals in dark resting site. This cluster formation results from self-organized amplification processes based on the modulation of the probability to move according to two factors: the number of surrounding individuals and the local light intensity. It means that this probability decreases with the number of congeners present and with the level of darkness [7] [8]. Then like cockroaches, Insbot will behave according to this simple rule.

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The aim of this study is to illustrate the building blocks needed to validate experimentally the behavioral patterns expressed by the cockroaches in presence of shelter and in presence of an Insbot. We will highlight the crucial role played by cuticular extracts of cockroach on the formation of mixed group.

Finally, we will test whether the Insbot is well integrated in the animal society and whether it does not disturb the collective decision-making and aggregation patterns. Therefore among, all the interactions, we will study the interactions between cockroaches and the influence of shelters and Insbots on cockroaches’ behavior (Fig. 1).

Fig. 1. All possible interactions between Insbots, cockroaches and shelters. A distinction was made either the reaction induce by the interaction was an attraction (+) or a repulsion (-).

2 Methods

Cockroaches (Periplaneta americana) were raised in transparent boxes (length: 80 cm; width: 40 cm; height: 100 cm). Water and food pellets were provided ad libitum. Cockroaches were kept under laboratory conditions at 25°C ± 1 in a 12h:12h light:dark cycle.

2.1 Experimental Setup and Procedure

Experiments were performed with adult male cockroaches. Following on the experiment conditions, 1, 10 or 30 adult cockroaches were picked up from the rearing box and isolated for 48 hours in the dark. They has access to water and food pellets. Animals with any external damage (e.g. missing antennal segments or legs) were discarded. After this isolation period, we introduced cockroaches in a circular arena (diameter: 100 cm) delimited by a black polyethylene ring (height: 20 cm, thickness: 1 cm) (Fig. 2a,b). To confine cockroaches in this experimental arena, its inner surface was covered by an electric fence (alternation of positively and negatively charged black aluminum layers (19 V, 0.2 A)).

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Fig. 2. A: Experimental setup composed of top camera (1), lamp (2), electrical fence (3), polyethylene ring (4), paper sheet (5), vibration absorbent layers (6) and wooden layer (7). Shelters are not represented on the illustration. The distance between lights and ground floor is 1.5 m. B: Experimental arena with two identical shelters.

The environmental conditions of the experimental setup were finely tuned in order to fit with cockroach and Insbot sensing capabilities. Firstly, temperature around the experimental setup was maintained at 20°C ± 1 since the walking speed of insects, like that of any insect, is highly sensitive to this factor. Secondly, since cockroaches mark the floor with a blend of different molecules (mainly hydrocarbons [10][11]), the white paper sheet (120g/m²) covering the ground of the arena (Fig. 2a) was renewed before each experiment. This prevents bias in cockroach behavior induced by the chemical marking deposited passively by congeners. In addition, the paper sheet was placed on two phonic layers which reduce the vibrations that could frighten the cockroaches. Finally, to prevent any disturbance of the cockroaches and the robots, lighting was exclusively artificial and produced by four neon lamp bulbs poor in IR (Fig. 2a, Philips ambiance Pro, 20 Watts, 355 lux ± 5 at ground level).

Two Plexiglas discs (diameter: 15 cm) were suspended 3 cm above the ground and positioned at 23 cm from the edge, symmetrically to the centre of the arena (Fig. 2b). Before each experiment, discs were cleaned with denatured ethanol (ethanol + ether). To obtain different luminosities under the shelters, we covered it with one (the light shelter with underneath 100 lux ± 5) or two layers (a.k.a. dark shelter with underneath 75 lux ± 5) of a red filter (Rosco color filter, E-Colour #019: Fire). The size of one shelter is large enough to contain up to 30 individuals, we did not observed any overcrowding. Due to the absence of red light-sensitive cells in their compound eye [12], cockroaches perceive an area illuminated by red light as shadow. When placed in an enlightened arena, these cockroaches have a higher probability to stop as soon as they enter the shadow area [13].

Concerning Insbot, they are able to distinguish the four main features of the setup: the light intensity under of shelters, the arena walls, the cockroaches and the other robots [14]. Behaviours of the Insbot are divided into two categories: reactive behaviours and higher level behaviours. At the exception of reactive behaviours (e.g. obstacle avoidance and wall following), every 500 ms, the robot had a probability to perform each of the three actions (turning, moving, or stopping) according to its

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position (centre or periphery; under a dark or bright) and the number of surrounding individuals (cockroaches or robots). These probabilities were determined from the observation of cockroach’s behaviours (for detail of Insbot’s behaviour see [14]).

Fig. 3. Two cockroaches and a chemically marked Insbot under a dark shelter (diameter: 15cm)

In addition the Insbot was wrapped into a paper dress (Whatman, grade 1 filter paper, 8.5cm) which covered the whole surface of the Insbot excepting sensors (Fig. 3). Onto this paper dress, we laid extracts of chemical compounds necessary to induce the aggregation process and to maintain the cohesion of aggregates. These compounds are mainly cuticular hydrocarbons which were extracted by immersing adult cockroaches in dichloromethane [10]. Sixty microliters of these extracts were laid on the tested Insbot, which is equivalent to the amount of compounds present on the cuticle of one cockroach (marked Insbot). A control test was carried out by using a paper-dressed Insbot covered impregnated with sixty microliters of dichloromethane only (unmarked Insbot).

The experiment began when cockroaches and/or an Insbot were introduced at the centre of the arena. All individual displacements were recorded by a camera for three hours (Fig. 1a, Fire-I Digital camera, Unibrain).

3 Results

3.1 Validation of the Experimental Setup Homogeneity

We had to test in our experimental setup whether two identical shelters have the same probability to be occupied by individuals. Indeed, the presence of external landmarks could lead to a higher selection rate by agents (animal or artificial) of one of the two identical shelters. In this latter case, we could not make a distinction between the respective contribution of the position of the shelter in the arena and of tested factors (luminosity, number of individuals it contains) on the observed aggregation pattern. Then, the analysis of the cockroach distribution under the shelters after 180 minutes of experiments, we can exclude the existence of any bias related to the position of the shelter in the arena which may favor its selection by the group at the expenses of the other shelter. Indeed, cockroaches have an equal probability (number of cockroaches

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under a shelter / total number of cockroaches under the two shelters) of 0.48 and 0.52 (305 cockroaches tested; Chi-square goodness of fit: χ²0.05,1 = 0.40, p > 0.05) to be found respectively under the left or the right light shelter.

Insbot can be influenced in its choices by any landmark external to the arena (for detail of sensor sensitivity see [14]). Tests with isolated Insbot (11 experiments for a total of around 8 hours of experiments) show that Insbot have an equal probability of 0.48 and 0.52 (number of entries = 147; Chi-square goodness of fit: χ²0.05,1 = 0.15, p > 0.05) to enter respectively in the left or in the right light shelter.

3.2 Perception of Shelters as Resting Site

The fraction of the total population (for one individual and groups of 10 or 30 cockroaches) under two identical dark shelters is significantly greater than the probability expected in case of homogeneous distribution of individuals in the arena (Table 1). This expected probability, that also assumes that the cockroaches do not interact together, is equal to the ratio between the area of the shelters (353.4 cm²) and the area of the arena (7853.8 cm²). Then, due to the low light intensity under shelters in comparison with the uncovered part of the arena, the two shelters constitute the only heterogeneities susceptible to focus the cockroach aggregation.

In table 1, we observe a high proportion of cockroaches aggregated under the shelters confirming that these heterogeneities are well perceived as resting sites. Indeed, one cockroach has a four times higher probability to be found out under shelters than expected from random. Furthermore, there is an enhancing group effect: when tested in groups of 10 or 30 individuals, more than a half of cockroaches are staying under the shelters. Hence the probability of a cockroach to leave a shelter decreases as the number of aggregated conspecifics increases. This confirms that the spatial distribution of the animals is not the simple summation of individuals’ resting preferences but also outcomes from interattraction effects.

Table 1. Comparison between probability of being under shelters resulting from a random homogeneous distribution of individuals in the arena and the observed probability of presence under shelters for 1, 10 or 30 cockroaches

Probability of presence

Random Observed 1 cockroach

(37 replicates) 0.045 0.20

10 cockroaches (30 replicates)

0.045 0.56

30 cockroaches (25 replicates)

0.045 0.62

This interattraction which plays a key-role in collective decision, is not only based on physical contacts but also on chemical attraction, due to the perception of cuticular blend of group members. Therefore, we have investigated whether the addition of

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these chemical compounds on Insbot may improve its integration within a cockroach’s group.

3.3 Chemical Marking and Insbot Integration in Mixed Society

To test to which extent the marking of Insbot with cuticular extracts of cockroaches is needed to allow the integration of the Insbot in a cockroach group, we compared individual and collective behavior of robot and insects in experimental tests with 10 cockroaches without Insbot, 10 cockroaches with an unmarked Insbot and 10 cockroaches with an Insbot chemically marked.

3.3.1 Influence on the Individual Behavior of Cockroach The level of acceptance of an Insbot by one cockroach is assessed by the mean time during which they stay close together under the same shelter.

The cockroaches are able to discriminate between an unmarked and a marked Insbot. Indeed, the mean time of contact between a cockroach and a marked Insbot is similar to the mean time between two cockroaches but lower than that between a cockroach and an unmarked Insbot (Fig. 4. Kruskal-Wallis test: KW = 14.3, 235 replicates, p < 0.001. Dunn’s multiple comparison test: p < 0.05 only for the comparison cockroach-cockroach vs cockroach-unmarked Insbot). The lack of agonistic behavior by the cockroach as well as its prolonged association with the marked Insbot confirms the successful acceptance of this marked artificial agent.

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Fig. 4. Mean time of contacts (± S.D.) under shelters between a cockroach and either another cockroach, a chemically marked Insbot or an unmarked Insbot. The duration of interactions between cockroach and robot are significantly different for the marked and unmarked robot.

3.3.2 Influence on the Collective Behavior of Cockroaches The integration of an Insbot in a group of cockroaches is assessed by its influence on the clustering behavior of cockroaches and its presence within animal clusters.

The unmarked Insbots seem to disturb the cockroach aggregation pattern. With an unmarked or a marked robot, respectively 40% or 70% of mixed society experiments ended by at least 66% of cockroaches under shelters (Fig. 5). This result shows that unmarked robot prevents the cockroaches from being under shelter.

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Fig. 5. Frequency distribution of experiments according to the proportion of aggregated cockroaches under shelter for experiments with marked or unmarked Insbot. The unmarked robots tend to lower the occurrence of large aggregates.

If we assumed that Insbot marked or not, has no influence on the aggregative choice of cockroaches, one would expect that the percentage of aggregated cockroaches would be similar in clusters including a robot or not. However, our observations show that the unmarked Insbot has a repulsive effect while the marked one attracts animals. Indeed, in only 30% of experiments, the majority of cockroaches (more than 2/3 of the total cockroach population) are with an unmarked Insbot under the same shelter (Fig. 6). On the other hand, around 60% of experiments with marked Insbot ended with the majority of sheltered cockroaches under the same shelter (Fig. 6).

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Fig. 6. Frequency distribution of experiments as a function of the proportion of cockroaches under the same shelter as either a marked or an unmarked Insbot. The insects prefer to aggregate by segregating the unmarked Insbots. If the robots are marked, the insects prefer to aggregate in the same shelter as the Insbots i.e. without segregation.

4 Conclusion

Many gregarious species are able to perform collective decision such as the selection of one resting site without being guided by the leader, simply due to local -often

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amplifying- interactions between group members. These collective decisions are not the simple summation of individual behavior (e.g. movement pattern, resting preference) but are deeply governed by a network of positive feedback loops. Hence, it is of the utmost importance to identify the nature and the specificities of amplifying interactions between group members in order to implement them in artificial agents and to build functional mixed societies. In accordance with the goals of the Leurre project [2], we are able to manage the behavioral and chemical parameters of the Insbot in order to integrate it in insect groups.

The good integration of robot in animal group through the formation of mixed aggregates namely depends on chemical recognition of robots by the cockroaches as a full member of the group.

We have validated the ability of the chemical lure put on Insbot to mimic interattraction between cockroaches. We highlight the crucial role played by cuticular extracts of cockroach on the formation of mixed group. Without chemical marking, the robot disturbs cluster formation and lead to spatial segregation from the insects. By contrast, with chemical marking, cockroaches share a shelter with the robot that could probably be perceived by the insects as a “congener”. Since the presence of one marked Insbot increases the resting time of a nearby cockroach, this artificial agent can nucleate the aggregation of animals and manipulate their spatial distribution. Besides, aggregation is a well known auto-catalytic process in which clustering increases with the number of already aggregated individuals. Therefore, in the future we will investigate how collective response of a mixed society will change with increasing number of artificial agents.

Acknowledgment

The LEURRE project [2] is funded by the Future and Emerging Technologies programme (IST-FET) of the European Community, under grant IST-2001-35506. G. Sempo is funded by “La Fondation des Treilles”, France and is research associate from the ECagents project of the European Community (IST-1940). C. Detrain and J.-L. Deneubourg are research associate from the Belgian National Fund for Scientific Research.

References

1. Colot, A., Caprari, G., Siegwart, R.: InsBot : Design of an Autonomous Mini Mobile Robot Able to Interact with Cockroaches. Proceedings of the 2004 IEEE International Conference on Robotics & Automation. New Orleans, LA (2004) 2418-2423

2. LEURRE Project official website, http://leurre.ulb.ac.be 3. Ishii, H., Nakasuji, M., Ogura, M., Miwa, H., Takanishi, A.:.Accelerating Rat's Learning

Speed Using a Robot - The robot autonomously shows rats its functions, Proceedings of the 2004 International Workshop on Robot and Human Interactive Communicaiton, Kurashiki, Okayama Japan (2004)

4. Kubinyi, E., Miklósi, A.., Kaplan, F., Gacsi, M., Topal, J., Cs anyi, V.: Can a dog tell the difference? dogs encounter AIBO, an animal-like robot in two social situations. Proceedings of the seventh international conference on simulation of adaptive behavior on From animals to animats. MIT Press, Cambridge (2002)

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5. Butler, Z., Corke, P., Peterson, R., Rus, D.: Virtual fences for controlling cows. Proceedings of the 2004 IEEE international Conference on Robotics & Automation New Orleans, LA April (2004) 4429- 4436

6. Vaughan, R., Sumpter, N., Henderson, J., Frost, A., Cameron, S.: Experiments in automatic flock control. Robotics and Autonomous Systems, 31 (2000) 109-117

7. Ame, J.M., Rivault, C., Deneubourg, J.L.: Cockroach aggregation based on strain odour recognition. Anim. Behav., 68 (2004) 793-801

8. Jeanson, R., Rivault, C., Deneubourg, J.L., Blancos, S., Fournier, R., Jost, C., Theraulaz, G.: Self-organized aggregation in cockroaches. Anim. Behav., 69 (2004) 169-180

9. Saffre, F., Halloy, J., Deneubourg. J.-L.: The Ecology of the Grid. Second International Conference on Autonomic Computing (ICAC'05) (2005) 378-379

10. Saïd, I., Costagliola, G., Leoncini, I., Rivault, C.:Cuticular hydrocarbon profiles and aggregation in four Periplaneta species (Insecta: Dictyoptera). J. Insect. Physiol., 51 (2005) 995-1003

11. Leoncini, I., Rivault, C.:Could species segregation be a consequence of aggregation processes. Example of Periplaneta americana (L.) and P. fuliginosa. Ethology, 111 (2005) 527—540

12. Mote, M.I., Goldsmith, T.H.: Spectral sensitivities of color receptors in the compound eye of the cockroach Periplaneta. Journal of Experimental Zoology, 173 (1970) 137-145

13. Meyer, D.J., Margiotta, J.F., Walcott, B.: The shadow response of the cockroach Periplaneta americana. Journal of Neurobiology, 12 (1981) 93-96

14. Tâche, F., Asadpour, M., Caprari, G., Karlen, W. and Siegwart, R.: Perception and Behavior of InsBot: Robot-Animal Interaction Issues. Proceedings of the IEEE International Conference on Robotics and Biomimetics, Hong Kong SAR and Macau SAR (2005)