In the previous decade, dozens of studies involving thousands of children across several research disciplines have made use of a combined daylong audio-recorder and automated algorithmic analysis called the LENA system, which aims to assess children's language environment. While the system's prevalence in the language acquisition domain is steadily growing, there are only scattered validation efforts on only some of its key characteristics. Here, we assess the LENA system's accuracy across all of its key measures: speaker classification, Child Vocalization Counts (CVC), Conversational Turn Counts (CTC), and Adult Word Counts (AWC). Our assessment is based on manual annotation of clips that have been randomly or periodically sampled out of daylong recordings, collected from (a) populations similar to the system's original training data (North American English-learning children aged 3-36 months), (b) children learning another dialect of English (UK), and (c) slightly older children growing up in a different linguistic and socio-cultural setting (Tsimane' learners in rural Bolivia). We find reasonably high accuracy in some measures (AWC, CVC), with more problematic levels of performance in others (CTC, precision of male adults and other children). Statistical analyses do not support the view that performance is worse for children who are dissimilar from the LENA original training set. Whether LENA results are accurate enough for a given research, educational, or clinical application depends largely on the specifics at hand. We therefore conclude with a set of recommendations to help researchers make this determination for their goals.

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While recent studies suggest children can use cross-situational information to learn words, these studies involved minimal referential ambiguity and the cross-situational evidence overwhelmingly favored a single referent for each word. Here we asked whether 2.5-year-olds could identify a noun's referent when the scene and cross-situational evidence were more ambiguous. Children saw four trials in which a novel word occurred with four novel objects; only one object consistently co-occurred with the word across trials. The frequency of distracter objects varied across conditions. When all distracter referents occurred only once (nocompetition), children successfully identified the noun's referent. When a high-probability competitor referent occurred on three trials, children identified the target referent if the competitor was absent on the third trial (short-competition) but not if it was present until the fourth trial (long-competition). This suggests that although 2.5-year-olds' cross-situational learning scales up to more ambiguous scenes, it is disrupted by high-probability competitor referents.Ambiguity and cross-situational learning 3

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Many fear that social networking sites (SNSs) are disconnecting people from meaningful face-to-face relationships. Nevertheless, previous research suggests that SNS use is related to increased face-to-face communication. The present study was conducted to determine whether personality traits and attachment styles moderate this relationship. Students (n ϭ 855) completed an online survey that included measures of Facebook use, time spent engaging in face-to-face communication, personality traits, and attachment styles. The results revealed that Facebook use was associated with increased face-to-face communication and that this relationship was moderated by extraversion. Specifically, the relationship between Facebook use and face-to-face communication was significant for individuals with low to moderate levels of extraversion (i.e., introverts) only. As extraversion increased, the magnitude of the relationship between Facebook use and face-to-face time decreased. No other personality traits or attachment styles significantly moderated the relationship between Facebook use and face-to-face communication. Facebook (and potentially SNSs more generally) may be especially beneficial for introverts by allowing them to build trust and rapport in a less threatening social environment that, in turn, makes them more comfortable engaging in face-to-face communication. However, research is needed to understand the direction and mechanisms underlying this relationship. Nevertheless, the present study provides novel insights into the beneficial role that Facebook may play in connecting people in the real world. Public Policy Relevance StatementIn young adults, more Facebook use was associated with increased time spent engaging in face-toface communication, and moderation analyses revealed that this association was only present in people with low to moderate levels of extraversion. No other personality traits or attachment styles moderated the association. These results suggest that Facebook use may be especially beneficial for fostering face-to-face relationships for introverts.