Summative research conducted over the years, including two landmark evaluations in 1970 and 1971, demonstrated that viewing the program had positive effects on young viewers' learning, school readiness, and social skills. Subsequent studies have replicated these findings, such as the effect of the show in countries outside of the U.S., several longitudinal studies, the effects of war and natural disasters on young children, and studies about how the show affected viewers' cognition. As CTW researcher Gerald S. Lesser stated in 1974, early tests conducted on the show (both formative and summative) "suggested that Sesame Street was making strides towards teaching what it had set out to teach".[2]