Thimerosal is a mercury-based preservative that has been used for decades in the United States in multi-dose vials (vials containing more than one dose) of medicines and vaccines. There is no evidence of harm caused by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site. However, in July 1999, the Public Health Service agencies, the American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure.
One group of mice, however, proved resilient to the stress. For three weeks before the social defeat treatment, all of the mice were subjected to two dramatically different living conditions. Some were confined to spartan cages, while others were treated to enriched environments with running wheels and tubes to explore. Unlike the mice in the bare-bones cages, bullied mice that had been housed in enriched environments showed no signs of rodent depression or anxiety after social defeat ( Journal of Neuroscience , 2011). "Exercise and mental enrichment are buffering how the brain is going to respond to future stressors," Lehmann says.
Studies of the Dunning–Kruger effect usually have been of North Americans, but studies of Japanese people suggest that cultural forces have a role in the occurrence of the effect.  The study Divergent Consequences of Success and Failure in Japan and North America: An Investigation of Self-improving Motivations and Malleable Selves (2001) indicated that Japanese people tended to underestimate their abilities, and tended to see underachievement (failure) as an opportunity to improve their abilities at a given task, thereby increasing their value to the social group.