The main way the success of environmental enrichment can be measured is by recognizing the behavioral changes that occur from the techniques used to shape desired behaviors of the animal compared to the behaviors of those found in the wild. Other ways that the success of environmental enrichment can be assessed quantitatively by a range of behavioral and physiological indicators of animal welfare. In addition to those listed above, behavioral indicators include the occurrence of abnormal behaviours (e.g. stereotypies, cognitive bias studies, and the effects of frustration. Physiological indicators include heart rate, corticosteroids, immune function, neuorobiology, eggshell quality and thermography.