Animacy is a fundamental yet difficult to define notion in cognitive science. For example, people judging whether words refer to entities that are alive are faster and more accurate for animals (e.g., tiger) than plants (e.g., petunia) and slower and less accurate for natural abiotic entities than artifacts (e.g., cave and ocean vs. slipper and bicycle). The current study demonstrates the reliability and validity of individuals’ aliveness judgments. 169 English-speaking Americans completed the aliveness study twice. Individual d-scores representing the difference in aliveness judgments between animals and plants at Session 1 predicted d-scores at Session 2 (r = .87, p < .001), as did d-scores representing the difference between natural abiotic entities and artifacts (r = .84, p < .001). These measures also predicted attitudes such as humans having the right to extract natural resources. Future research must address how differences in environment/culture contribute to differences in animacy cognition.