  Face-to-face interactions are important for a variety of individual behaviors
and outcomes. In recent years a number of human sensor technologies have been
proposed to incorporate direct observations in behavioral studies of
face-to-face interactions. One of the most promising emerging technologies are
active Radio Frequency Identification (RFID) badges. They are increasingly
applied in behavioral studies because of their low costs, straightforward
applicability, and moderate ethical concerns. However, despite the attention
that RFID badges have recently received, there is a lack of systematic tests on
how valid RFID badges are in measuring face-to-face interaction. With two
studies we aim to fill this gap. Study 1 (N = 11) compares how data assessed
with RFID badges correspond with video data of the same interactions (construct
validity) and how this fit can be improved using straightforward data
processing strategies. The analyses show that the RFID badges have a
sensitivity of 50% that can be enhanced to 65% when flickering signals with
gaps of less than 75 seconds are interpolated. The specificity is relatively
less affected by this interpolation process (before interpolation 97%, after
interpolation 94.7%) - resulting in an improved accuracy of the measurement. In
Study 2 (N = 73) we show that self-report data of social interactions
correspond highly with data gathered with the RFID badges (criterion validity).
