Iconicity has traditionally been considered an objective, fixed, unidimensional property of language forms, often operationalized as transparency for experimental purposes. Within a Cognitive Linguistics framework, iconicity is a mapping between an individual’s construal of form and construal of meaning, such that iconicity is subjective, dynamic, and multidimensional. We test the latter alternative by asking signers who differed in ASL proficiency to complete a handshape monitoring task in which we manipulated the number of form–meaning construals that target handshapes participated in. We estimated the interaction of iconicity, proficiency, and construal density using mixed-effects models for response time and accuracy with crossed random effects for participants and items.Results show a significant three-way interaction between iconicity, proficiency, and construal density such that less-proficient signers detected handshapes in more iconic signs faster than less iconic signs regardless of the handshape they were monitoring, but highly proficient signers’ performance was only improved by iconicity for handshapes that participate in many construals. Taken in conjunction with growing evidence of the subjectivity of iconicity, we interpret these results as support for the claim that construal is a core mechanism underlying iconicity, both for transparent and systematic language-internal form–meaning mappings.