I also assume that they are not simply the physical properties of things as now conceived by physical science. Instead, they are ecological, in the sense that they are properties of the environment relative to an animal.

(1979). Perceiving Acting and Knowing: Toward an Ecological Psychology. ).

In his classic work The Perception of the Visual World (1950) he rejected the then fashionable theory of behaviorism for a view based on his own experimental work which pioneered the idea that animals 'sampled' information from the 'ambient' outside world. They are all prosperous.