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. 2016 Oct 10;6:34615.
doi: 10.1038/srep34615.

On The Evolutionary Origin of Symbolic Communication

Free PMC article

On The Evolutionary Origin of Symbolic Communication

Paul Grouchy et al. Sci Rep. .
Free PMC article


The emergence of symbolic communication is often cited as a critical step in the evolution of Homo sapiens, language, and human-level cognition. It is a widely held assumption that humans are the only species that possess natural symbolic communication schemes, although a variety of other species can be taught to use symbols. The origin of symbolic communication remains a controversial open problem, obfuscated by the lack of a fossil record. Here we demonstrate an unbroken evolutionary pathway from a population of initially noncommunicating robots to the spontaneous emergence of symbolic communication. Robots evolve in a simulated world and are supplied with only a single channel of communication. When their ability to reproduce is motivated by the need to find a mate, robots evolve indexical communication schemes from initially noncommunicating populations in 99% of all experiments. Furthermore, 9% of the populations evolve a symbolic communication scheme allowing pairs of robots to exchange information about two independent spatial dimensions over a one-dimensional channel, thereby increasing their chance of reproduction. These results suggest that the ability for symbolic communication could have emerged spontaneously under natural selection, without requiring cognitive preadaptations or preexisting iconic communication schemes as previously conjectured.


Figure 1
Figure 1. NoiseWorld.
Robots exist in a 2D world and can sense their own x and y locations. They cannot sense any information about their neighbours. Robots can produce nondirectional sounds ωout and can detect the sounds produced by their nearest neighbour ωin. Robots live on one of the islands in the world, and when two robots meet, they automatically produce one offspring. A randomly selected robot dies whenever a new offspring robot is born. Islands are organized in a toroid. Offspring robots are occasionally born on one of the four neighbouring islands.
Figure 2
Figure 2. A sample history of an island is examined and top reproducing robots from two different eras are shown interacting.
The top frame of these behaviour samples shows the trajectory that the two robots take, while the bottom frame shows their communication outputs ωout over time. Auditory interpretations of ωout values are provided in Supplementary Audio S1–S2. An era is 100,000 timesteps. (a) By era 313, indexical communication has emerged. One can determine directly a robot’s absolute y position at a given timestep from its ωout value (y = ωout/4.36, see text). (b) By era 937, symbolic communication has emerged. Robot position information can no longer be determined from observing single ωout values. Instead, relative robot positions are revealed through sign-sign relationships (i.e., by observing both agents’ ωout values, see text). (c) Reproduction rates are shown with (green) and without (grey) communication enabled. (d) Also shown are the magnitudes of the Pearson product-moment correlation coefficients between the position (y in red, x in blue) and ωout of each era’s most reproductively successful agent.
Figure 3
Figure 3. Various visualizations of the evolved communication output ωout.
(a) Neighbouring robots determine relative y positions via their ωout/in (i.e., dialogue) values oscillating between the two separate regions shown here. The ωout/in of the robot with the higher y value will settle in the left region (resulting in a higher ωout), while the other settles in the right region (resulting in a lower ωout), thus “deciding” relative north/south robot position. (b) As the two robots approach a common y position (the nonlinear part of these plots), the robot with the smaller x position will see the magnitude of its ωout increase faster than that of its neighbour, which in turn forces the neighbour’s ωout back towards linear behaviour, thus “deciding” their relative east/west position.
Figure 4
Figure 4. The genome of an agent with an evolved symbolic communication scheme is embodied in two e-puck robots.
Agents are supplied with their position information via an overhead webcam and colour detection software. Evolved agents are run on a laptop (not shown) that handles communication between agents and sends instructions to the robots via Bluetooth. Two hardware experiments are shown, with images taken at 5 second intervals shown in the first row, and the corresponding inter-robot communication data shown underneath. Auditory interpretations of ωout values are provided in Supplementary Audio S3–S4.

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