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Groupitizing reflects conceptual developments in math cognition and inequities in math achievement from childhood through adolescence.

Groupitizing – the ability to take advantage of grouping cues to rapidly enumerate sets that otherwise require serial counting – is linked to conceptual aspects of numbers (accessing the cardinality of subgroups) and math (combining the subgroups values) that rapidly emerge during the first years of schooling (Starkey & McCandliss, 2014). Little else is known about its broader role in mathematical development. This study followed the development of groupitizing skill from late childhood through early adolescence (N = 1,209), revealing a pattern of progressive development over these critical years for math achievement. Individual differences were highly predictive of global math achievement from 3rd to 8th grade, above and beyond socioeconomic and cognitive (domain-general and math-specific) predictors. Experimental manipulations of item grouping cues (number of subgroups, numerical composition of subgroups) lead to similar effects that manipulations of operands have on symbolic mathematical reasoning, corroborating the view that groupitizing draws upon the same conceptual processes as symbolic math even in the absence of well-learned symbolic retrieval cues. Finally, we show that groupitizing provides new cognitive insights into the nature of the socioeconomic status achievement gap, which cannot be fully explained by familiarity with specific symbolic math facts learned in school but rather suggest inequities in educational opportunities that promote flexible mastery of conceptual processes. Taken together, groupitizing – as a non-symbolic assessment of conceptual processes in mathematics – could be a critical tool in implicitly assessing math ability.