Other studies have reinforced the effect of environmental enrichment on self-administration, such as one that showed it reduced re-instatement of cocaine seeking behavior in mice through cues (though not if that re-instatement was induced by cocaine itself) and another that showed it can eliminate previously established addiction-related behaviors. Furthermore, removing mice from enriched environments has been shown to increase vulnerability to cocaine addiction and exposure to complex environments during early stages of life produced dramatic changes in the reward system of the brain that resulted in reduced effects of cocaine.