A more recent meta-study summarizing five different studies concluded that infants are born with an innate ability to differentiate quantities within a small range, which increases over time. By the age of seven that ability increases to 4-7 objects. Some practitioners claim that with training, children are capable of subitizing 15+ objects correctly.

Abacus

The hypothesized use of yupana, an Inca counting system, placed up to five counters in connected trays for calculations.

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