Language Acquisition and Cognitive Development

Research project P 14495 Language Acquistition and Cognitive Developement Josef PERNER 26.6.2000 This project investigates the relationship between cognitive and linguistic developments in the preschool years (2 to 7 years). The focus is on the critical developments of understanding the mind (theory of mind), counterfactual and causal reasoning, and mastery of the grammatical structures that are typically used to verbally express these cognitive domains. For instance, in order to understand what people want, believe, or say it is necessary to understand that the content of their desires, beliefs and utterances need not be true. So the question is whether children become able to understand these mental states and acts of communication (assessed in a non-linguistic way) at the same time as they become able to tackle the grammatical complexity of embedded sentences, i.e., the matrix verb (e.g., say, think, want) and the embedded complement (content of what is said, thought, desired). Another example is children`s ability to understand counterfactual conditionals. John took the bus to the mountains: Where would he be if he had not taken the bus but the train (which goes to the lake)? We investigate whether children can master such problems regardless of their complexity at a particular age and whether it coincides with their understanding of false beliefs and the grammatical form of the subjunctive in a variety of contexts. As a longer term goal we hope to develop the specific linguistic problems used in our project into test items for an easy to administer grammar test that assesses appropriate items for the preschool period.

We investigated children`s linguistic and cognitive development in three different domains. (1) Understanding Falsehood. In this part we investigated deVillier`s theory that children younger than four years have difficulty understanding mental states (e.g., desires and beliefs), because they have not yet acquired the prerequisite syntactic structure for talking about mental states, i.e. sentential complements (e.g., "Mum thinks that Andy goes to bed"). In a series of experiments with 3 to 5 year old German speaking children we found challenging evidence for this theory. In fact, the majority of the 3-year-olds had already acquired the sentential complement structure for verbs of desire ("Die Mutter will, dass"), although they had still difficulties understanding mental states. This finding suggests that the acquisition of that-complements can not be a prerequisite for understanding mental states. (2) Understanding Counterfactually. Our investigation of the development of counterfactual thinking (e.g., "what if A had happened and not B) and its relationship with children`s understanding of mental states confirmed that both abilities develop within the same age span (3 to 5 years). We also tested the proposal that counterfactual thinking is a necessary prerequisite for understanding mental states. However, several experiments suggested that this might not be the case. Rather, there seems to be a dissociation of counterfactual thinking and understanding mental states, and the relationship reported in previous studies is most likely due to a coincidental similarity of complexity of the two tasks used to measure these abilities. (3) Substitutability of co-referential expressions. Our studies of children`s ability to alternatively name the same object with two different labels (e.g., rabbit and animal) confirmed that this ability develops around the age of 4 years. Moreover, we found a strong and robust correlation between alternative naming and understanding mental states. We explain this unusual relationship in terms of both abilities requiring an understanding of perspective. Furthermore, we also investigated children`s understanding of the non- substitutability of co-referential expressions in opaque contexts (e.g., mental states). For example, consider Heinz knows that there is a ball in the box but does not know that the ball is his birthday present. In this case, only the sentence "Heinz knows that there is a ball in the box" is true, but not, "Heinz knows that his present is in the box". The results of a series of experiments suggest that children have problems understanding the non-substitutability of co-referential expressions until they are 5 or even 6 years old.