The Sibling Effect: What the Bonds Among Brothers and Sisters Reveal About Us By Jeffrey Kluger Reviewed by Margarita Tartakovsky, M.S.   I am what science calls a singleton. And according to G. Stanley Hall, a psychologist, professor and the first president of the American Psychological Association, I am without a doubt narcissistic, spoiled and … More The Sibling Effect: What the Bonds Among Brothers and Sisters Reveal About Us | Psych Central