A Minnesota researcher has performed psychological testing on 50 homeless people and found that about 20 of them were suffering from dementia or other serious brain damage. As a result many of them have qualified for Social Security disability benefits. Many of the homeless people may have been born with cognitive limitations. Drug abuse and alcoholism may have caused more brain damage. Others may have suffered brain damage as a result of assaults suffered while living on tough streets. Similar research is underway in at least two other locations.