Deng et al. treat mobility as a constitutive condition of environmental exposure rather than a nuisance variable surrounding fixed places. Their review of thirty-three mobile-method studies shows that greenspace, affect and wellbeing become analytically unstable when exposure is followed through daily trajectories: definitions vary, spatial and temporal windows shift, and equivalent instruments can generate non-equivalent findings. The paper’s strongest operation is to make spatiotemporal variability itself methodological evidence. Intensive longitudinal designs, ecological momentary assessment, GPS and mobile sensing allow researchers to study within-person changes as encounters unfold, but only if exposure, affect and sampling are specified with sufficient consistency. The proposed framework responds to fragmentation by identifying geographic scope, sampling, affect measurement, exposure specification and statistical technique as dimensions requiring coordination. The wider intellectual bridge is to time geography and environmental psychology: environments are not merely locations occupied by subjects, but changing sequences of contact whose duration, timing and movement pattern condition what an exposure can mean.
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