For example, researchers have found that many rats and mice in laboratories are obese from excess food and minimal exercise which alters their physiology and drug metabolism. Many laboratory animals, including mice and rats, are chronically stressed which can also negatively affect research outcomes and the ability to accurately extrapolate findings to humans. Researchers have also noted that many studies involving mice, rats and other rodents are poorly designed, leading to questionable findings. One explanation for deficiencies in studies of rodents housed in laboratory cages is that they lack access to environmental agency and thus the ongoing freedom to make decisions and experience their consequences. By housing rodents under extreme impoverished conditions, these captive animals bear diminished resemblance to humans or their wild conspecifics.