Paivio's (1975) additivity hypothesis suggests that simultaneous stimuli from different sources enhance the recall of an item. However, little is known about the additivity of pictures and spoken words in reading conditions where participants are allowed time to generate inner speech and mental imagery. The present experiment investigates the existence of additivity in the learning of second-language concrete vocabulary by presenting up to three types of stimuli simultaneously. Participants are 50 anglophone college students learning Spanish as a second language. The results obtained suggest that when inner speech and mental imagery occur, adding extra stimuli does not improve recall. Under these circumstances, recall seems to depend more on word length and on individual learning strategies that probably consist of mental rehearsing and linking new items to already stored information.
