1. Ackley, D., & Littman, M. (1994). Altruism in the evolution of communication. In R. Brooks & P. Maes (Eds.), Arti#cial Life IV (pp. 40--48 ). Cambridge, MA: MIT Press.

2. Arita, T., & Koyama, Y. (1998). Evolution of linguistic diversity in a simple communication system. Arti#cial Life, 4, 109--124.

3. Axelrod, R., & Hamilton, W. (1981). The evolution of cooperation, Science, 211, 1390--1396.

4. Benz, J. (1993). Food-elicited vocalizations in golden lion tamarins: Design features for representationa l communication. Animal Behavior, 45, 443--455.

5. Bradbury, J. W., & Vehrencamp, S. L. (1998). Principles of animal communication. Sunderland , MA: Sinauer.

6. Brown, C. R., Brown, M. B., & Shaffer, M. L. (1991). Food-sharing signals among socially foraging cliff swallows. Animal Behavior, 42, 551--564.

7. Caine, N. (1995). Factors affecting the rates of food calls given by red-bellied tamarins. Animal Behavior, 50, 53--60.

8. Caraco, T., & Giraldeau, L.-A. (1991). Social foraging: Producing and scrounging in a stochastic environment . Journal of Theoretical Biology, 153, 559--583.

9. Chapman, C. A., & Lefebvre, L. (1990). Manipulating foraging group size: Spider monkey food calls at fruiting trees. Animal Behavior, 39, 891--896.

10. Cheney, D., & Seyfarth, R. (1990). How monkeys see the world. Chicago: Chicago University Press.

11. Clutton-Brock, T., O'Riain, M., Brotherton, P., Gaynor, D., Kansky, R., Grif#n, A., & Manser, M. (1991). Sel#sh sentinels in cooperative mammals. Science, 284, 1640--1644.

12. de Bourcier, P., & Wheeler, M. (1995). Aggressive signaling meets adaptive receiving . In F. Moran, A. Moreno, J. Merelo, & P. Chacon (Eds.), Advances in arti#cial life (pp. 760--771). Berlin: Springer.

13. Dittus, W. P. J. (1984). Toque macaque food calls: Semantic communication concerning food distribution in the environment . Animal Behavior 32, 470--477.

14. Elgar, M. A. (1986). House sparrows establish foraging #ocks by giving chirrup calls if the resources are divisible . Animal Behavior 34, 169--174.

15. Elowson, A., Tannenbaum, P., & Snowdon, C. (1991). Food-associated calls correlate with food preferences in cotton-top tamarins. Animal Behavior 42, 931--937.

16. Hamilton, W. (1996). The genetical evolution of social behavior. Journal of Theoretical Biology 7, 1--51.

17. Hauser, M. (1996). The evolution of communication. Cambridge, MA: MIT Press.

18. Hauser, M., & Marler, P. (1993). Food-associated calls in rhesus macaques (Macaca mulatta ): I. Socioecologica l factors. Behavioral Ecology 4, 194--205.

19. Hauser, M., & Marler, P. (1993). Food-associated calls in rhesus macaques (Macaca mulatta ): Costs and bene#ts of call production and suppression. Behavioral Ecology 4, 206--212.

20. Hauser, M. D., Teixidor, P., Field, L., & Flaherty, R. (1993). Food-elicited calls in chimpanzees: Effects of food quantity and divisibility . Animal Behavior 45, 817--819.

21. Heinrich, B., & Marzluff, J. M. (1991). Do common ravens yell because they want to attract others? Behavioral Ecology and Sociobiology, 28, 13--21.

22. Holland, J. (1975). Adaptation in natural and arti#cial systems. Ann Arbor: University of Michigan Press.

23. Holmes, W. (1984). Predation risk and foraging behavior of the hoary marmot in Alaska. Behavioral Ecology and Sociobiology, 15, 293--302.

24. Hutchins, E., & Hazlehurst, B. (1995). How to invent a lexicon. In N. Gilbert & R. Conte (Eds.), Arti#cial societies (pp. 157--189). London: UCL Press.

25. Judd, T., & Sherman, P. (1996). Naked mole-rats recruit colony mates to food sources. Animal Behavior, 52, 957--969.

26. Koza, J. (1992). Genetic programming. Cambridge, MA: MIT Press.

27. Luke, S., & Spector, L. (1998). A revised comparison of crossover and mutation in genetic programming. In J. Koza, W. Banzhaf, K. Chellapilla , K. Deb, M. Dorigo, D. Fogel, M. Garzon, D. Goldberg, H. Iba, & R. Riolo (Eds.), Proceedings of the Third Annual Conference on Genetic Programming (pp. 208--214). San Francisco: Morgan Kaufmann.

28. Macedonia, J. M., & Evans, C. S. (1993). Variation among mammalian alarm call systems and the problem of meaning in animal signals. Ethology, 93, 177--197.

29. MacLennan, B. (1990). Evolution of communication in a population of simple machines. (Tech. Rep. No. CS-90-99). Knoxville: University of Tennessee.

30. MacLennon, B. (1991). Synthetic ethology: An approach to the study of communication. In C. G. Langton, C. Taylor, J. D. Farmer, & S. Rasmusen (Eds.), Arti#cial life II (pp. 631--658). Redwood City, CA: Addison-Wesley.

31. Milinski, M., & Heller, R. (1978). In#uence of a predator on the optimal foraging behaviour of sticklebacks (Gasterosteus Aculeatus). Nature, 275, 642--644.

32. Newman, J. A., & Caraco, T. (1989). Cooperative and non-cooperative bases of food-calling. Journal of Theoretical Biology, 141, 197--209.

33. Nowak, M., & Sigmund, K. (1993). A Strategy of win stay, lose shift that outperforms tit-for-tat in the prisoners-dilemma game. Nature, 364, 56--58.

34. Nowak, M., & May, R. (1992). Evolutionary games and spatial chaos. Nature, 359, 826--829.

35. Pereira , M., & Macedonia, J. (1991). Ringtailed lemur antipredator calls denote predator class, not response urgency. Animal Behavior 41, 543--544.

36. Rasa, O. A. (1989). The costs and effectiveness of vigilance behavior in the dwarf mongoose: Implications for #tness and optimal group size. Ethology, Ecology and Evolution, 1, 265--282.

37. Reggia, J., Schulz, R., Uriagereka, J., & Wilkinson, J. (2000). A simulation environment for evolving multi-agent communication. Tech. Rep. College Park: University of Maryland , Dept. of Computer Science.

38. Seyfarth, R., Cheney, D., & Marler, P. (1980). Vervet monkey alarm calls: Semantic communication in a free-ranging primate. Animal Behavior 28, 1070--1094. Arti#cial Life Volume 7, Number 1 31 J. A. Reggia et al. Evolution of Inter-Agent Signaling

39. Sherman, P. W. (1977). Nepotism and the evolution of alarm calls. Science, 197, 1246--1253.

40. Sherman, P. (1985). Alarm calls of Belding 's ground squirrels to aerial predators: Nepotism or self-preservation ? Behavioral Ecology and Sociobiology 17, 313--323.

41. Steels, L., & Kaplan. F. (1998). Stochasticity as a source of innovation in language games. In C. Adams, R. Belew, H. Kitano, & C. Taylor (Eds.), Arti#cial Life VI (pp. 368--376). Cambridge, MA: MIT Press.

42. Steels, L., & Kaplan, F. (1999). Collective learning and semiotic dynamics. In D. Floreano, J. Nicoud, & F. Mondada (Eds.), Advances in arti#cial life (pp. 679--688). Berlin: Springer.

43. Wade, M. (1980). Kin selection: Its components. Science, 210, 665--667.

44. Wagner, K. (1999). Habitat, communication and cooperative strategies. In W. Banzhof, J. Daida, A. Eiben, M. Garzon, V. Honover, M. Jakiela, & R. Smith Proceedings of the Genetic and Evolutionary Computation Conference (pp. 694--701). San Francisco: Morgan Kaufmann.

45. Wagner, K. (2000). Cooperative strategies and the evolution of communication. Arti#cial Life, 6, 149--179.

46. Werner, G., & Dyer, M. (1991). Evolution of communication in arti#cial organisms. In C. G. Langton, C. Taylor, J. D. Farmer, & S. Rasmusen (Eds.), Arti#cial life II (pp. 659--687). Redwood City, CA: Addison-Wesley.

47. Werner, E., Gilliam, J., Hall, D., & Mittelbach, G. (1983). An experimental test of the effects of predation risk on habitat use in #sh. Ecology, 64, 1540--1548.

48. Wilkinson, G. S., & Boughman, J. W. (1998). Social calls coordinate foraging by greater spear-nosed bats. Animal Behavior 55, 337--350.

49. Wrangham, R. (1977). Feeding behavior of chimpanzees in Gombe National Park, Tanzania. In T. Clutton-Brock (Ed.), Primate ecology (pp. 503--538). London: Academic Press.