<p>Measurement is about finding structure in a set of objects (or events). It is about associating a set of objects whose structure we wish to understand with a set of formal objects, typically numbers, whose structure we understand. Underlying measurements are the four types of scales (nominal, ordinal, interval, and ratio), which differ in how much information they provide about the objects being measured. These scale types are classified into those that involve a unit of measurement (interval and ratio) and those that do not (nominal and ordinal). In this paper, we make use of this distinction to formulate a hypothesis about the nature of human concepts. We suggest that humans and only humans mentally represent concepts that rely on measurement scales that invoke a unit (i.e. interval and ratio scales). We test this uniqueness claim in the context of social cognition and show that this hypothesis provides a principled account of why certain forms of sociality are only observed in human relations. We highlight the fact that the significance of measurement scales in the study of cognition in general and human cognition in particular is yet to be appreciated.</p>