Affect as well as object properties impact measurement estimations.

The probability of perceiving objects in a group as being similar to each other is a negative exponential function of the distance between them in a psychological space (Shepard 1987). Here I summarize results from recent experimental studies showing that the psychological distance and thereby the similarity between objects of the same category depends on object properties such as size, frequency, and manipulability. For example, people judged elephants to be more different from each other than ants are. Further results show that irrelevant object properties evoked by digit-word expressions modulate numerosity estimations. For example, people judged “8 elephants” to be more numerous than “8 ants”. Taken together, these findings demonstrate that individuals need not directly perceive specific object properties in order to develop numerosity estimation biases (cf. Binet 1890) but promptly and unduly take into account irrelevant object properties when the objects are being merely mentioned, suggesting that words can instantly access rich mental representations that subsequently affect measurement estimations. Additional experimental findings suggest that emotional states can also impact measurement estimations.