Retrieval Dynamics of In-the-Moment and Long-Term Statistical Word Learning

Retrieval Dynamics of In-the-Moment and Long-Term Statistical Word Learning Haley A. Vlach (haleyvlach@ucla.edu) Catherine M. Sandhofer (sandhof@psych.ucla.edu) Department of Psychology, University of California, Los Angeles 1285 Franz Hall, Los Angeles, CA 90095 USA Abstract Memory. Research on human memory has long sought to discover the conditions of learning that (a) create and store a representation of knowledge and (b) produce a representation that can be recalled and accessed over extended periods of time. This body of research has revealed several learning conditions that promote long-term memory. For example, distributing practice (e.g., Bjork & Allen, 1970), varying the conditions of practice (e.g., Smith & Rothkopf, 1984), and reducing feedback to the learner (e.g., Schmidt, 1991) have all been shown to promote long- term memory. These learning conditions support long-term memory because they introduce difficulty for learners while knowledge is being acquired (see Bjork, 1994, for a review). Although introducing difficulty during learning often deters immediate performance, retention tests reveal higher long- term performance (compared to easier learning conditions). Because of the long-term benefit of such difficulties, these conditions of learning are often termed „desirable difficulties‟ of learning (e.g., Bjork, 1994). Consequently, memory research suggests that creating difficulty during learning promotes long-term performance. An example of a desirable difficulty of learning is distributed practice, often termed the spacing effect (e.g., Vlach, Sandhofer, & Kornell, 2008). The spacing effect is the robust phenomenon whereby memory is enhanced when learning events are distributed across time (i.e., spaced), instead of being presented in immediate succession (i.e., massed). Because of the time between learning events, spaced learning creates greater opportunities for forgetting (e.g., Bjork & Allen, 1970). Consequently, retrieving previous learning events is more difficult. On the other hand, massed presentations prevent forgetting because presentations are in immediate succession, making retrieval of previous learning events easier. In fact, upon immediate testing, massed presentations lead to a greater amount of learning than spaced presentations. However, if a test is administered following a delay, a spaced presentation schedule will yield more learning than the massed presentation schedule (e.g., Vlach et al., 2008). Theories of word learning have proposed several tools that children and adults use to reduce the difficulty of the word learning problem. However, we propose that reducing difficulty may be detrimental—difficulty may promote long-term word learning. In this study, we tested predictions of desirable difficulties and the retrieval effort hypothesis in a cross- situational word learning paradigm. Learners were presented with objects and labels in three conditions of learning (easy, medium, and difficult) and tested either immediately or one week later. Results revealed a counterintuitive pattern of performance—initially, participants in the easy condition had the highest performance. However, after a one week delay, participants in the medium condition had the highest performance. Participants‟ self-report of retrieval difficulty during learning is used to account for differences in performance over time. This work is discussed in terms of the implications for several fields of cognitive science: statistical learning, human memory, and language and cognitive development. Keywords: word and category learning; statistical learning; cross-situational learning; language and cognitive development; Introduction Word learning has been described as one of the greatest challenges of cognitive development. The world offers learners a seemingly infinite number of word-to-world mappings yet children and adults appear to learn words with great ease (Quine, 1960). How do learners accomplish such a difficult task? Theories of word learning have focused on tools that learners use to make the word learning problem easier. These tools range from basic cognitive processes of attention (e.g., Smith, 2000), to social cues (e.g., Tomasello & Barton, 1994), to early constraints, such as mutual exclusivity (e.g., Markman, 1989). Although theories of word learning propose different mechanisms and tools, all theories suggest that reducing difficulty of the task is beneficial for word learning. In this study, we take a radically different perspective on word learning. We propose that the difficulty children and adults encounter during word mapping may be beneficial to the learning process. That is, a desirable amount of difficulty may promote long-term word learning. We examine how difficult learning conditions affect learners‟ in-the-moment and long-term statistical word mapping. We take a mechanistic approach by examining a basic cognitive process that contributes to different learning outcomes: retrieval difficulty during learning. Taken together, this work demonstrates the central role of retrieval processes in statistical learning and word mapping. Word Learning. Word learning tasks differ from memory tasks. In memory tasks, learners are asked to store a specific piece of information and then retrieve that piece of information later. However, in word learning tasks, children and adults are required to aggregate and abstract across learning events in order to infer and/or generalize to a new experience.