Many event descriptions are true only when the event comes to its natural end point: e.g., a “feeding” event culminates when the feed-ee has eaten, not simply when food is provided. Do non-linguistic event conceptualizations reflect attention to natural culmination points? We tested adults and 14-month-olds to ask: provided two events with the same ACTION but different ENDPOINTs - one a naturally expected result, the other only partially achieved - do adults and infants perceive them as members of the same event category or of different categories? Adults were asked to rate the similarity between the two events; infants were habituated to one event and tested for dishabituation when it was switched to the other. Adult data suggest the difference between a complete and a partially-complete event is registered, and carries more psychological weight than a mere perceptual difference. Infant data (ongoing) will show the developmental origin of such conceptualizations.