WATER IS NOT H2O

What makes a liquid water? A strong version of ''psychological essenti alism'' predicts that people use the presence or absence of H2O as the primary determinant of what liquids they call ''water.'' To test this prediction, subjects were asked to judge the amount of H2O in liquids called ''water'' and liquids not called ''water.'' Neither their beli efs about the simple presence/absence of H2O nor about the proportion of H2O in the liquids accounted well for which ones are normally calle d ''water.'' Typicality ratings and an extended tree solution on simil arity ratings suggested that use, location, and source of a liquid may also influence whether it is considered to be water. Sentence accepta bility judgments further suggested that there may be a sense of ''wate r'' that corresponds to the strong essentialist view, but that there i s also a more general sense in common use encompassing mixtures with v arying amounts of H2O. These findings indicate that essentialist belie fs alone may not fully explain category membership judgments and word use, and they suggest a modified version of psychological essentialism . (C) 1994 Academic Press, Inc.