The Spanish pronominalized infinitival construction is characterized by variable singular and plural verb agreement between the perception verb, the perceived participant and the subordinate infinitive. Traditional accounts relate this formal variability to a different reading of the construction, namely a passive (variable singular vs. plural concord) vs. impersonal (always singular) interpretation. This paper argues that variable agreement in the pronominalized infinitive construction is another case of agreement ad sensum, a widespread phenomenon in Spanish. It relates the formal alternation to a strategy used by the speaker to foreground a particular conceptualization of the perception stimulus (the perceived participant or the event as a whole). This ties up with the general nature of the perception act (object perception vs. event perception), and depends, to a considerable extent, on the modality (visual vs. auditory) of the main perception verb.