This paper investigates the idiosyncratic understanding of universal quantifiers such as every, each or all by young children at the ages of 4 to 7, and argues that the phenomenon is explicable in terms of the maturation of both the cognitive system and the linguistic system. Evidence for this dual explanation comes from the fact that the visual input, a picture, plays a key role in determining the children`s conceptual representation, suggesting the need for the central integration of visual and linguistic elements; and from the fact that a quantifier in the linguistic input has an intrinsic property, i.e. a < +focus > feature. I have tried to explain the nature of cognitive factors in terms of the function of the central system, suggesting a modified form of Smith & Tsimpli’s (1995) version of Fodor’s (1983) modularity hypothesis. The categorial status of the quantifier in the children`s interpretation is considered, focusing on the movement of that quantifier out of its own extended projection to FP. It is claimed that children initially treat quantifiers as modifiers, rather than functional heads, and that the phenomenon of quantifier spreading by children can be attributed to delay in the development of the relevant functional category, i.e., DP (or QP), in language acquisition. (Kookmin University)