Another example of the work of converging operations is in looking for a cause of Korsakoff's syndrome, a severe memory loss which is often the only disabling symptom experienced. (Pinel, 2002). Because it commonly occurs in alcoholics, the syndrome was originally believed to be caused by the toxic effects of alcohol on the brain, as in the case with Jimmie G. (Pinel, 2002).
Later it was discovered that Korsakoff's syndrome is caused by thiamine (vitamin B1) deficiency (Pinel, 2002). The syndrome occurs in malnourished persons who consume little or no alcohol. Thiamine-deprived rats showed memory loss and brain damage similar to Korsakoff's syndrome in human alcoholics. Alcohol may also have a direct toxic effect on the brain because it accelerates the brain damage in thiamine-deprived rats.
Thus, the convergent evidence here states that Korsakoff's syndrome frequently occurs in alcoholics, first, because often most of the calories they consume comes from alcohol, which lacks vitamins; second, because alcohol interferes with metabolism of the thiamine they do consume; and third, because alcohol accelerates the brain damage produced by the lack of thiamine.
The converging operations here included: neuropsychological case reports like Jimmie G's, quasi-experiments studying alcoholics, quasi-experiments studying thiamine deficient non-alcoholics, controlled animal experiments manipulating thiamine levels and finally effects of thiamine supplementation in humans. Reaching the correct conclusion about the cause of Korsakoff's syndrome would have been impossible without the use of all of the above methods.
Strong inference
Since one cannot prove a theory, the best way to show support for a particular theory is by the method of strong inference - by disproving as many opposing to it theories as possible, while showing support for the main theory (Platt, 1964). Converging operations provide strong inference.