{Reference Type}: Journal Article {Title}: Continuous measurement of dynamic classroom social interactions. {Author}: Messinger DS;Prince EB;Zheng M;Martin K;Mitsven SG;Huang S;Stölzel T;Johnson N;Rudolph U;Perry LK;Laursen B;Song C; {Journal}: Int J Behav Dev {Volume}: 43 {Issue}: 3 {Year}: 2019 May {Factor}: 3.021 {DOI}: 10.1177/0165025418820708 {Abstract}: Human observations can only capture a portion of ongoing classroom social activity, and are not ideal for understanding how children's interactions are spatially structured. Here we demonstrate how social interaction can be investigated by modeling automated continuous measurements of children's location and movement using a commercial system based on radio frequency identification. Continuous location data were obtained from 16 five-year-olds observed during three 1-h classroom free play observations. Illustrative coordinate mapping indicated that boys and girls tended to cluster in different physical locations in the classroom, but there was no suggestion of gender differences in children's velocity (i.e., speed of movement). To detect social interaction, we present the radial distribution function, an index of when children were in social contact at greater than chance levels. Rank-order plots indicated that children were in social contact tens to hundreds of times more with some peers than others. We illustrate the use of social ties (higher than average levels of social contact) to visualize the classroom network. Analysis of the network suggests that transitivity is a potential lens through which to examine male, female, and mixed-sex cliques. The illustrative findings suggest the validity of the new measurement approach by re-examining well-established gender segregation findings from a new perspective.