The study by Norman Geschwind and Peter Behan investigates the association between left-handedness, immune diseases, migraine, and developmental learning disorders. They conducted two studies to test the hypothesis that left-handed individuals and their families have a higher frequency of these conditions. In the first study, they found significantly higher rates of immune diseases and learning disabilities in left-handed subjects compared to right-handed controls. The second study compared the frequency of left-handedness in patients with migraine or immune disorders to general population controls, finding a higher percentage of left-handedness in severe migraine patients and those with myasthenia gravis. The authors propose a hypothesis involving testosterone's role in both brain development and immune system maturation, suggesting that testosterone's effects on the left hemisphere may contribute to the observed associations. They also discuss the potential genetic factors involved in the familial clustering of these conditions.The study by Norman Geschwind and Peter Behan investigates the association between left-handedness, immune diseases, migraine, and developmental learning disorders. They conducted two studies to test the hypothesis that left-handed individuals and their families have a higher frequency of these conditions. In the first study, they found significantly higher rates of immune diseases and learning disabilities in left-handed subjects compared to right-handed controls. The second study compared the frequency of left-handedness in patients with migraine or immune disorders to general population controls, finding a higher percentage of left-handedness in severe migraine patients and those with myasthenia gravis. The authors propose a hypothesis involving testosterone's role in both brain development and immune system maturation, suggesting that testosterone's effects on the left hemisphere may contribute to the observed associations. They also discuss the potential genetic factors involved in the familial clustering of these conditions.