Learning to talk about motion UP and DOWN in Tzeltal: Is there a language-specific bias for verb learning?

The spatial vocabulary of the Mayan language Tzeltal is dominated by an Absolute system of spatial reckoning, whereby an "uphill/downhill" coordinate abstracted from the lay of the land is used to reckon spatial relationships on the horizontal in both small-scale and long distance space. This system is used in lieu of a Front/Back/Left/Right system which does not exist in this language. The spatial vocabulary dedicated to this system (which I refer to in general as the UP/DOWN vocabulary) includes intransitive motion verbs (roughly translatable as "ascend"/"descend"), their transitivized counterparts ("make it ascend/descend"), directional adverbs ("uphillwards"/"downhillwards"), and possessed relational nouns ("uphill/downhill in relation to it"). This same vocabulary applies to spatial relations on the vertical axis. Two seemingly contradictory observations about children's early meanings for the spatial verbs dedicated to this system motivate the proposal put forward in this paper. On the one hand, Tzeltal children's UP/DOWN vocabulary shows very early sensitivity to the semantic structure of the language they are learning: the meanings for these verbs are from the first usages attached to the slope of the land, and to particular places; there is no evidence of an initial preference for the vertical meaning. On the other hand, children's meanings remain for a long time too specific, and errors of interpretation/production (using the verbs to mean 'local slope of land' rather than 'overall N/S slope of land direction) are evident in verbal productions of some children as late as age 7 or 8. The proposal is made that the highly specific nature of Tzeltal verbs at the basic level influences the children's hypotheses about what kinds of meanings verbs can have