I'm not up on the literature but I've seen the regular rat raising environments, it's a small plastic box with an absorbent material bedding, a wire lid and a water bottle nozzle, nothing else, someone tosses in some rat chow once a day. Possibly able to see blurry images of other rats through the sides of the box. So, about as stimulating as a russian orphanage. Stressful even, for animals that would normally be engaged in activities like exploring and chewing. Makes one wonder if "regular" versus "environmentally enriched" is fair terminology, maybe, "severely neglected" and "has a bit of environmental complexity" would be closer to it.
Which doesn't answer your actual question at all.
Polly
