Cross-linguistically, the semantic extensions of certain adpositions obey an implicational scale, ranging from thesituation class of prototypical ON (support from below) to prototypical IN (full containment) (Bowerman & Pederson 1992,Levinson & Meira 2003, Feist 2008). However, the nature of this phenomenon remains unresolved. Two general accounts arepossible: 1) the patterned output is the simply the result of diachronic factors and speakers learn which extensions go with eachadposition without any particular analysis, or 2) there may be some online psychological reality to the scale.Language learning may be a fruitful domain to test this second account. Using an artificial language learning paradigm,subjects are trained on alternative forms paired with scenes representing some situation classes on the scale. In testing, theygeneralize the use of these forms to novel classes. Preliminary findings suggest a generalization of forms to uses in waysconsistent with a psychological representation.

It is well known that listeners of probably all languages give verbal and non-verbal signals, called backchannels, to their interlocutors. However, it is not well understood what drives listeners to backchannel. To what degree are they an indicator of listener attention? Are backchannels semantically motivated, performed when the message has been parsed and comprehended? Or are they automatic responses triggered by overt cues from the speaker (such as eye contact, gestures, or prosodic information), requiring minimal comprehension? An important first step in answering this question is identifying what overt speaker cues trigger backchannels, and to what degree. This preliminary study looks at storytelling data from conversational dyads. We find that the speaker cue most likely to ‘successfully’ trigger a backchannel is making eye contact. Interestingly, however, other cues are more likely to trigger different kinds of backchannels: gestural cues trigger more head nods, while prosodic cues trigger more verbal backchannels.