y y -axis Y chromosome Y maze y prime y-coordinate y-intercept Y-linked y′ yagé yakee Yale model yantra Yates’s correction for continuity yaupon yawning yea-saying Yerkes–Dodson law Yerkish yes–no task yin and yang yoga yohimbine yoked-control group you statement young male syndrome young-old Young–Helmholtz theory of color vision Youngberg v. Romeo youpon youth counseling youth culture Yule’s Q