TABLE 2—

Proximal and Distal, Spatiotemporal Scale Versus Level—Meanings, Contrasts, and Causal Implications

	Spatiotemporal Scale
Category	Space	Time	Level
Metric of distance	Units of spatial distance, measured in nested increments; examples include: kilometer–meter–millimeter– micron; or mile–foot–inch	Units of temporal distance, measured in nested increments; examples include: millennium– century–year–day–hour–minute–second– millisecond	Adjacency of levels, which can be organized—theoretically, conceptually, or structurally—as nested or nonnested hierarchies; examples include:
			nested: nation–region–city–neighborhood–household; or ecosystem–species–organism–organ system–organ–cell; nonnested: school | workplace | neighborhood–individual
“Near”	Proximal, near in space, close	Proximal, near in time, recent	Conceptual or structural nonscalar relationship: adjacent levels
“Far”	Distal, distant in space, far away	Distal, distant in time, long ago	Conceptual or structural nonscalar relationship: nonadjacent levels
Strength of effect	Usually inverse relationship of spatial distance and force: closer = stronger, hence proximal = powerful; farther = weaker, hence distal = dilute	Usually inverse relationship of temporal distance and force: closer = stronger, hence proximal = powerful; farther = weaker, hence distal = dilute	Cannot predict “strength” of “effect” based solely on level: a given phenomenon at any given level potentially can powerfully or weakly affect or be affected by phenomena at the same level, adjacent levels, and nonadjacent levels
Typical causal inference	Proximal = stronger cause Distal = weaker cause	Proximal = stronger cause Distal = weaker cause	Causal inference depends on level of question being asked: There may be different explanations for phenomena at different levels, and explanations for events observed within any given level may involve solely phenomena within that level or also interactions between levels; adjacency of levels may or may not predict causal strength of cause–effect relationship
Relationship to space and time	Physical distance is a spatial dimension distinct from time, but space and time can be related mathematically, e.g., distance = speed × time (and the length of a meter is now defined in relation to time and the speed of light32[p537])	Chronological distance is a temporal dimension distinct from space, but time and space can be related mathematically, e.g., time = distance/speed (and initial time units were based on the earth’s rotation, involving spatial distance32[pp3–5])	Level is not a spatiotemporal phenomenon. It is, instead, a conceptual nonspatiotemporal relational construct that organizes and distinguishes (conceptually or structurally) different orders of hierarchically linked systems and processes (including both nested and nonnested hierarchies). “Distance” for levels does not involve spatiotemporal separation: For any phenomenon at any given point in space and time, all levels co-occur simultaneously, even though some levels may be more causally relevant than others to phenomena occurring at any given level. Space and time nevertheless do matter for levels in the case of nested hierarchies, whereby units within lower-order levels typically are smaller and involve faster processes than units in higher-order levels.