Cardinal directions refer to the four main points of direction in geographical space: north, south, east, and west. Efficientnavigation requires some basic knowledge about cardinal directions. We evaluated developmental changes in cardinaldirection knowledge in real space. Tested in an unfamiliar indoor environment with a window view, 94 children aged 6-12years old were asked to point to North and then point to East. We proposed 7 developmental stages based on knowingthe horizontal plane of cardinal directions, the inter-relationships between them, and how to identify north using referenceframes. Our classification scheme classified all participants and was sensitive to age differences. Our results suggested thatidentifying north was more difficult than knowing the inter-relationships. Many children were not able to use an allocentricreference frame effectively. Overall, our study demonstrates the utility of our classification scheme and the importance ofevaluating cardinal direction knowledge development in children.

We present a skill learning model Clarion. Different from existing models of high-level skill learning that use a topdown approach (that is, turning declarative knowledge into procedural knowledge), we adopt a bottom-up approach toward low-level skill learning, where procedural knowledge develops first and declarative knowledge develops later. Clarion is formed by integrating connectionist, reinforcement, and symbolic learning methods to perform on-line learning. We compare the model with human data in a minefield navigation task. A match between the model and human data is found in several respects.

This paper introduces a hybrid model that unifies connectionist, symbolic, and reinforcement learning into an integrated architecture for bottom-up skill learning in reactive sequential decision tasks. The model is designed for an agent to learn continuously from on-going experience in the world, without the use of preconceived concepts and knowledge. Both procedural skills and high-level knowledge are acquired through an agent's experience interacting with the world. Computational experiments with the model in two domains are reported.

Forty-two adolescents with Down syndrome (DS) ages 10 to 21 years completed a battery of language and phonological memory measures twice, 2 years apart. Individual differences were highly stable across two years. Receptive vocabulary scores improved, there was no change in receptive or expressive grammar scores, and nonword repetition scores declined. Digit memory and expressive vocabulary scores improved among younger adolescents, but generally held steady among older adolescents. These patterns may reveal key points in development at which interventions may be best applied. Further research is needed to understand specific processes in tasks that appear to be slowing or declining during adolescence. They may be important for understanding early aging and dementia in DS.