Evidence of the use of extensive and intensive quantity concepts in experienced readers of cartographic maps

Geographers have a shared intuition about geographic information, but this intuition is not well understood. In this work, we study the extent to which geo-analysts of varying skill levels possess the ability to distinguish between cartographic representations of two kinds of quantities, extensive quantities which can be summed, and intensive quantities which cannot. Data were collected from two sample groups in two online experiments. Participants were first tasked to select the odd-one-out from three maps with the same visualization style, and second to choose whether a given data attribute best fits a choropleth or a proportional symbol map visualization. The results show GIS expertise and cartographic skill predict answer accuracy and extensive quantities are distinguished correctly significantly less than intensive quantities.