Multiple Proposal Memory in Observational Word Learning

Multiple Proposal Memory in Observational Word Learning Judith Koehne (judith.koehne@uni-bamberg.de) Otto-Friedrich-Universitat Bamberg Markusplatz 3, 96045 Bamberg John C. Trueswell (trueswel@psych.upenn.edu) Lila R. Gleitman (gleitman@psych.upenn.edu) Institute for Research in Cognitive Science, University of Pennsylvania, 3401 Walnut Street, Suite 400A, Philadelphia, PA, USA Abstract hne & Crocker, 2011). An important aspect that is ignored in these studies, however, is the role that each learner’s in- dividual learning path plays. It is therefore unclear whether one and the same person in fact stores multiple possibilities for a word and if this is the case, under which circum- stances. One factor that has been shown to be relevant to this question is the order in which the language novice has encountered and re-encountered potential referents (Medina et al., 2011). We evaluate the way learners exploit observational word learning situations within two experiments, employing the standard paradigm of psychologically investigating cross- situational word learning. Importantly, we consider both the learner’s individual learning path and the order of exposures and re-exposures of potential referents. We moreover ad- dress the possibility that the different outcomes in different studies may be due to the implemented experimental proce- dure. In particular, we compare a procedure, in which par- ticipants make a choice on each learning trial (Exp. 1) to a passive look-and-listen learning phase (Exp. 2). The temporal co-occurrence of a novel word and a visual ref- erent undoubtedly facilitates establishing the meaning of a word. It is less understood, however, how precisely learners can keep track of the frequencies of these co-occurrences across situations. Observational learning may rely on one or few highly informative exposures (propose-but-verify) or it may be driven by the collection of evidence in a more gradual and parallel manner (multiple-hypotheses tracking). We evaluated both hypotheses within two experiments and found that learners were able to keep track of more than one hy- pothesis for a novel word. However, this memory was strongly dependent on each learner’s individual learning path (i.e., which meanings they had considered before) and influ- enced by the order of presentation of potential referents. We argue for an account of a multiple-proposal memory rather than a multiple co-occurrence memory. Keywords: observational word learning; memory; cross- situational analysis; multiple hypotheses tracking; propose- but-verify; individual learning paths Observational Word Learning While observing the world can be a very direct path to the meaning of a novel word (fast mapping, Carey, 1978), the relationship between both sources of input is often too am- biguous to make a promising immediate guess. The learner could solve this problem in various ways: On each learning instance, she could store multiple possible solutions and then identify the best solution across several learning in- stances through an intersective process, an assumption that is commonly understood to underlie the idea of cross- situational word learning (Quine, 1960; Yu & Smith, 2007). Alternatively, she could make an immediate guess about the word’s meaning and wait for confirmation or rejection. In this case, the learner would have no memory for the alterna- tives that were not guessed, but maximally a memory for the different guesses tried along the way until the correct one is identified. While experiments reported in Medina, Snedeker, Trueswell, & Gleitman (2011) and Trueswell, Medina, Ha- fri, & Gleitman (2013) support this latter idea (propose-but- verify account), other studies indicate that learners are able to extract multiple hypotheses on each learning instance (Vouloumanos, 2008; Vouloumanos & Werker, 2009; Koe- Learning based on Co-occurrence Frequencies Trueswell et al. (2013) examined learners’ memory in ob- servational learning situations in a series of experiments. During the learning phase, participants were presented two or five visual referents and a spoken sentence containing one novel noun per trial. The task was to choose that refer- ent (by mouse click) in each trial that the learner believed to match with the novel noun. Trueswell et al. found that even if the learning situations were greatly simplified but still ambiguous (just two possible referents), participants later showed no sign of memory for any referent other than the one they had selected. Specifically, when a learner re- encountered a noun (e.g., mipen), he was at chance at select- ing the correct referent (e.g., bear) if he had made the wrong choice the previous time he had encountered mipen (e.g., if he had chosen door rather than the correct bear). Had he remembered that the unselected (but correct) referent (bear) had co-occurred with mipen, he could have unambiguously identified it as correct in the current situation. Interestingly, other studies indicate that learners are able to precisely differentiate the co-occurrence frequencies of different alternatives for one noun. Vouloumanos (2008)