Umwelt and the observer-dependent environment

Bayliss discusses drainage or diversion theories, in which a stream of excitation is diverted to a different course by an easier way. Bayliss gives William James as the first to express the theory and says von Uexküll gave it more definite form, using the names tonus and excitation for what flows through the neuro-muscular mechanisms¹. McDougall is named as another who spoke of a stream of energy¹. The passage does not use the word umwelt. It shows only that von Uexküll's name was already tied to an account of how excitation is organised inside the animal.

Lyon (2015), in The cognitive cell, contrasts definitions of cognition that stress psychological elements with those of authors concerned with its biological manifestation. Lyon lists James, Jennings, von Uexküll, Lorenz, Gibson and Maturana among the second group, who stress the ecological context in which information is used². Reid (2023) cites von Uexküll (1926) among sources for a classic line between cognitive and non-cognitive organisms. On that line, non-cognitive organisms react to stimuli without internal feedback between receptor and site of action⁸. Reid then reports sensorimotor feedback systems without neurons, and cites Baluška and Levin that neurons are ill-deserving of their special reputation⁸.

Fields, Glazebrook and Levin (2021) argue against a common assumption. Theories of consciousness, they say, typically place the agent in an environment with observer-independent features and objects⁴. The visual system is often described as using inverse optics to compute an observer-independent three-dimensional layout from a two-dimensional image⁴. They claim that this assumption restricts the agent to a subset of our own ontology and risks under-predicting its computational needs. They add that it makes von Uexküll's question of defining the umwelt, and Nagel's question of what it is like, harder⁵. They also tie stable object identity to memory and the perception of time, and say an organism with these has a meaningful umwelt even if its ontology differs from ours⁶.

Levin (2019) argues that individual cells each measure local conditions at the cell surface. When coupled by gap junctions, the collective can measure and act on the same sensory data, and the umwelt expands into a larger individual³. Levin (2022) calls Nagel's question a first-order step. The second-order question asks what it is like to be a caterpillar becoming a butterfly, whose umwelt changes as the brain is reassembled⁷. Shreesha and Levin (2024) note that their stress model was judged by an external observer's error function. They state that it is not known what it is like to be a cell or tissue under stress⁹.