In this study, we introduce a novel system whereby a humanoid robot, named Alter3, employs a selective combination of three strategies - Mimicking, Imitation, and Dream - to replicate human behavior observed through its camera-based eyes. This work builds upon previous research [Masumori et al. (2021); Ikegami et al. (2021)]. In Mimicking mode, Alter3 recreates “how” a human moves by calculating joint angles. In Imitation mode, it identifies and reproduces symbolic poses through a pre-trained Variational AutoEncoder (VAE), essentially replicating “what” the human did. When imitation proves unsuccessful, Alter3 engages its Dream mode, where it recalls altered memories through selection and mutation processes, allowing it to generate movements based on experience. Moreover, in the absence of a human subject, Alter3, with its eyes closed, retrieves and performs movements from memory. Our findings reveal that the concurrent use of the three strategies (Mimicking, Imitation, Dreaming) stabilizes the latent space state and optimizes the range of identifiable poses. Furthermore, the behavior that Alter3 generates through Dream mode evolves from symbolic movements via the Imitation pathway. These findings suggest that new movements can be created from concept-based motions by selectively employing both methodical (Mimicking) and symbolic (Imitation) motions.

Acoustic ecologist Bernie Krause hypothesized that rich soundscapes in mature ecosystems are generated by sound communication between different species with differentiating acoustic niches. This hypothesis, called the acoustic niche hypothesis, proposes that in a mature ecosystem, the singing of a species occupies a unique bandwidth in frequency and shifts in time to avoid competition, thus making the communication efficient. We hypothesize that selective pressure on communication complexity is required for differentiating and filling acoustic niches by a limited number of species, in addition to selective pressures on communication efficiency. To test this hypothesis, we built an evolutionary model where agents can emit complex sounds. Our simulations with the model demonstrate that selective pressure on communication efficiency and complexity leads to an evolution in spectral differentiation with a limited number of species filling the acoustic niche. This is the first demonstration of acoustic niche differentiation using an artificial life model with complex-sounding agents. We also propose multi-timescale complexity measurement, extending the Jensen–Shannon complexity using multi-scale permutation entropy. We analyze the evolved soundscape in the simulations using this measure. The result shows that multi-timescale complexity in soundscape evolved, suggesting that evolving niche differentiation leads to ecological complexity. We implement the extended model in real space and demonstrate that the system can adaptively generate sounds, differentiating acoustic niches with environmental sounds.