Coherent collective behavior emerges from local interactions between individuals that generate group dynamics. An outstanding question is how to quantify group coherence in order to understand the nature of these dynamics. We investigate this problem in the context of a small group of pedestrians instructed simply to walk to a goal. To measure the degree of coordination in a group, we employed principal components analysis to estimate dimensional compression, and cross-recurrence quantification analysis to estimate the coupling strength between individuals. The results indicate lower-dimensional behavior and more stable coupling in real groups compared to reshuffled virtual groups. These findings demonstrate spontaneous local coordination in pedestrian groups that gives rise to coherent collective behavior, and offer an approach for investigating group dynamics in more complex contexts.