This article relates adults' difficulty acquiring foreign languages to the associative learning phenomena of cue salience, cue complexity, and the blocking of later experienced cues by earlier learned ones. It examines short-and long-term learned attention effects in adult acquisition of lexical (adverbs) and morphological cues (verbal inflections) for temporal reference in Latin (1 hr of controlled laboratory learning) and Spanish (three to eight semesters of classroom learning). Our experiments indicate that early adult learning is characterized by a general tendency to focus on lexical cues because of their physical salience in the input and their psychological salience resulting from their simplicity of form-function mapping and from learners' prior first language knowledge. Later, attention to verbal morphology is modulated by cue complexity and language experience: Acquisition is better in cases of cues of lesser complexity, speakers of morphologically rich native languages, and longer periods of study. Finally, instructional practices that emphasize morphological cues by means either of preexposure or typographical enhancement increase attention to inflections thus to block reliance on adverbial cues. This study explores adults' difficulty acquiring foreign languages (L2s) in terms of cognitive principles of transfer-in particular, attentional processes in the associative learning of form-meaning relations in linguistic constructions.