And blind here is a technical term meaning she had no idea what the baby saw, and the point about this is to avoid either intentional or unintentional sort of trying to get the answer you want.

这里的盲性是个术语,意味着主试完全不知道婴儿看到了什么,这样做的目的在于,避免主试因想要得到自己所想要的结果,而进行的有意或无意的尝试

耶鲁公开课 - 心理学导论课程节选