A theoretical challenge for cognitive science is to explain both the presence and absence of systematicity. Oneexplanation (Phillips & Wilson, 2010) says systematicity derives from universal constructions. We tested this theory with anexperiment that required learning cue-target pair maps whose underlying structures were either products (universal construc-tion), or non-products (control). Each series was learned in either ascending or descending order of size: number of uniquecue/target elements constituting pairs, which varied from three to six. Only performance on the product series was affectedby order: systematicity was obtained universally in the descend group, but only on large sets in the ascend group. The resultssuggest that learning small maps directly, without reference to the underlying product, may be perceived as more cost-effective,i.e., acquisition of a universal construction, hence systematicity, depends on an empirical cost-benefit tradeoff.

Theories of cognition that posit complementary dual-route processes afford better fits to the data when each routeexplains a part of the data not explained by the other route. However, such theories must also explain why each route isinvoked, lest one can fit any data set with enough routes. One possible explanation is that route selection is based on a least-costprinciple: the route that requires fewer cognitive resources (including time) relative to the goal at hand. We investigated thisexplanation with a dual-route version of visual search, where the target could be identified via opposing (easy or hard formsof) feature and conjunction search conditions. The data support a contextualized version of the least-cost principle in that thecost of computing least-cost also influences route selection: participants assessed alternatives, but only when the cost of thatassessment was relatively low.