What does 'reality base' mean? Can it be replaced by just 'reality'?
The more meaning we can construct from transactions with the environment, the broader our reality base.
Article - 'Meaning and visual metaphor' by Hermine Feinstein
reality base is another way of saying: a basis in reality. However, this is in language, here, visual metaphor or language.
That said, this would be an opinion as most of this art criticism language lends itself to opinions and interpretation.
The author is "locating" (as they say in this type of writing) meaning in transactions with the environment. As a reader, at first glance, that means (for me) inter-actions with the environment.
It is not clear what this environment is made up of.
"Reality base" is the maximum range of things from reality that we can reach, and build upon.
Consider this metaphor: Our understanding of reality, our understanding of everything, is like constructing a building. The broader, thicker, stronger, and deeper the foundation of that building, the broader and taller we can build on top of that foundation. Expanding the bottom-most base of the building expands what we are able to build up on top of that base.
I believe the author is saying that things like art and metaphor expand the range of things we can understand about reality, that they expand the range of knowledge and understanding that we can build about reality. It expands the range of things we can think and perceive and know. It expands the range of science we can understand and invent and use, it expands the range of social-constructs we can understand and invent and use.
Note that people are a part of reality. Note that society is a part of reality. Expanding our "reality base" - which includes things like art and metaphor - expands our ability to understand and relate with other people in valuable ways. It expands what kind of society we are able to build.