Supervisors: professor Renate Pajusalu (Tartu Ülikool) ja professor Reili Argus (Tallinna Ülikool)
Opponent: professor Klaus Laalo (Tampere ülikool)
The development of the acquisition of basic cognitive categories - the categories of space, person, time and number - on both linguistic and non-linguistic conceptual level has been considered very important. The research area of this PhD thesis is the acquisition of the categories of time and tense in Estonian which, in addition to the acquisition of tense, focuses mainly on the lexical means of expressing time, i.e. time adverbs. The general goal of the thesis is to investigate the development of the temporal system of Estonian speaking children up to 7 years of age. In the thesis I have particularly concentrated on two questions: 1) in which order do the time adverbs appear in the speech of Estonian children in the beginning of the development of the temporal system and in which sense are the first time adverbs used; 2) which are the connections between the acquisition of the lexical category of time and the grammatical category of tense, in particular: do time adverbs help children perceive and use tense forms. The main results and conclusions of the thesis about the acquisition of the category of time by 1- to 7-year-old children are the following: (1) The acquisition of lexical time begins simultaneously with the acquisition of tense, shortly before the age of two. The first time adverbs are deictics referring to the temporal relation from the point of speech time. The expression of lexical time begins with the present time - the first time adverbs that occur refer to or specify present time. After that, both the expression of the past by grammatical and lexical means as well as the expression of the future by time adverbs become more frequent, the use of sequential time adverbs is also frequent in child language. Time adverbs occur in the child's repertoire mostly by imitating what the adult has said. In further development they are mainly placed in the temporal context but during the early period of language acquisition random placement into temporal context is also characteristic to time adverbs (e.g. homme kukkus 'fell tomorrow'). (2) By four years of age Estonian children have not yet completely acquired the category of time, at 4 to 7 years of age active acquisition of the category of time takes place. The results of the experiment show that time adverbs constitute important temporal information for the comprehension and production of tense forms. While the time adverbs enne 'before', praegu 'now', pärast 'after' are more clear for children than the semantically more complex time adverbs juba 'already', jälle 'again', veel 'still, yet' when expressing temporal sequence both sets of words help perceive and use verb tense.