Abstract
The System Blocks are a collection of communicating blocks that enable children (and adults) to explore dynamic behavior. A set of wooden boxes with embedded computation, the blocks enable children to physically interact with stocks, flows, time-delays and feedback loops. The System Blocks is one of the research projects conducted at the Lifelong Kindergarten group, headed by Prof. Mitchel Resnick at the MIT Media Laboratory.

Background
Forrester has argued that in order to learn the 'deeper lesson' of dynamic systems we should train our mental models using computer simulations. Epistemological and child development researchers have found that interaction with the physical world is a critical factor in the development of a child's mental model. Friedrich Froebel and later Maria Montessori have pioneered the field of manipulative materials in education. Froebel, who created the world's first kindergarten in Germany in 1837, developed a specific set of 20 "gifts" -- physical objects such as balls, blocks, and sticks -- for children to use in the kindergarten. Froebel carefully designed these gifts to help children recognize and appreciate the common patterns and forms found in nature. Froebel's gifts were eventually distributed throughout the world, deeply influencing the development of generations of young children. Indeed, Frank Lloyd Wright credited his boyhood experiences with Froebel's gifts as the foundation of his architecture [2]. Maria Montessori extended Froebel's ideas, developing materials for older children and inspiring a network of schools in which manipulative materials play a central role. Today, manipulative materials are well-established in the classroom, especially in the early grades. Education journals are filled with papers on ways of using manipulative materials in the classroom -- papers with colorful titles such as "Lima Beans, Paper Cups, and Algebra" [8] and "Activities to Grow On: Buttons, Beads, and Beans" [5].

Current implementation
The System Blocks are designed for straight-forward physical interaction, with no need for programming or insertion of equations. Each block has an input and output ports and a pre-defined mathematical operation. A system is constructed by connecting the blocks in different arrangements, using cables and connectors. Unlike SD software simulation tools, equations cannot be changed which limits the variety of systems the blocks can simulate.

The following is a list of the different behaviors implemented at this stage. Our aim is to experiment with different sets of behavior and see which one is the most applicable for a k-5 audience. The blocks are a de-centralized system, with no central management. Each block receives input, performs its own operation and sends the result through the output cables. This architecture limits the functionality, but enables free exploration of different arrangements and assures scalability.

The Senders - there are two types of Senders blocks. The continuous block sends a continuous stream of numbers to the next block. A slider allows the child to dynamically select the values. The discrete block sends a stream of 0's, and when it's button is clicked, sends a single number to the next block.
The Accumulator - receives input and stores it. The input can be received from a 'plus' or a 'minus' port, which will add or subtract the input from the accumulated level.
The Delay - receives input, holds it for X seconds and sends it to the next block. A slider allows the child to dynamically select the delay value.
The Multiplier - receives inputs, multiplies them and sends the result to the next block.
The MIDI - receives input and plays the MIDI note associated with that number (0 - 127). Following is an example scenario, simulating simple accumulation using the discrete block as an input to the accumulator block. The MIDI block and speakers are used to play the increasing or decreasing accumulator level, using a standard piano scale. The child can connect the discrete block to the plus or minus ports of the accumulator, and control the accumulator level.

The same scenario can be constructed using one or two continuous blocks as input, to reach a status of 'dynamic equilibrium' using the same values on each block (flow-in and flow-out are the same). More complex behaviors can be constructed by adding the delay block between the input blocks and the accumulator (delay the flow-in or the flow-out), or by connecting the accumulator back to itself and forming a feedback loop.

Summary and next steps
The system blocks project is currently under development. Our next steps are to collaborate with system dynamics teachers, test the blocks in a classroom environment and gather feedback. Based on the testing results, the blocks behaviors might be adapted to match the Stella 'building blocks' so it fits more easily into existing SD curriculum. Other forms of media are planned on top of the current MIDI sound output. A level or graph display might be one; an electric motor or lamp might be another. The vision is to create a playful construction kit that contributes to a gradual development of a 'systems mental model', helping children to intuitively understand dynamic behavior in their day-to-day lives.

For more information about the author and the Lifelong Kindergarten group at MIT:
http://llk.media.mit.edu
http://www.media.mit.edu/~orenz