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The PSLC Theoretical Hierarchy

Although the PSLC does not espouse a single theory of learning, it does encourage its researchers to maximize the overlap between each other’s theories. That is, to the maximum extent possible, a PSLC researcher’s explanation should use the same terminology and hypotheses as other PSLC researcher’s explanations

In order to display the integration achieved by this form of collaboration, the PSLC maintains a theoretical hierarchy. When a set of explanations share many terms and hypotheses, we make a node for each explanation, make a node for their common features, and link the nodes so that the common-feature node is the parent of each explanation node. Although in many cases a node is a single wiki page, we use the term traditional term “node” to refer to it so that there will be no confusion when a node corresponds to several wiki pages

In order to more clearly display the integration, each node contains:

  1. An abstract that briefly describes the research encompassed by the node;
  2. A glossary that defines terms used elsewhere in this node but not defined in the nodes that are parents, grandparents, etc. of this node;
  3. The research question stated as concisely as possible, usually in a single sentence;
  4. The dependent variables, which are observable and typically measure competence, motivation, interaction, meta-learning, or some other pedagogically desirable outcome;
  5. The independent variables, which are typically include instructional environment, activity or method, and perhaps some student characteristics, such as gender or first language;
  6. The hypothesis, which is a concise statement of the relationship among the variables that answers the research question;
  7. An explanation, which is short (a paragraph or two) and typically mentions unobservable, hypothetical attributes of the students (e.g., the students’ knowledge or motivation) and cognitive or social processes that affect them;
  8. The descendents, which lists links to descendent nodes of this one, if there are any;
  9. An annotated bibliography, which lists documents (as hyper links and/or references in APA format) and indicates briefly their relationship to the node (e.g., whether the document reports the node in full detail, or describe the design of a study that has not yet been run, or describes a similar study that is not quite the same as the one described by the node, etc.).

Experience suggests that the glossaries carry much of the load in explaining the research, and that carefully defining and exemplifying terms often pays off later in reducing confusion and facilitating collaboration. Consequently, the glossaries are sometimes so long that they are spit off as separate wiki pages.

The root node of the hierarchy represents the research question addressed by the PSLC as a whole. It is necessarily abstract and is not the sort of question that can actually be tested by a single decisive experiment. This node is maintained by the PSLC co-directors.

The immediate descendents of the root node are three nodes representing the research questions address by each of the PSLC research clusters. That is, there are nodes for each of Coordinative Learning, Interactive Communication and Refinement and Fluency. These present somewhat more concrete research questions. They are specializations to the center’s overarching questions, and form a bridge to testable hypotheses posed by individual research projects. These 3 nodes are maintained by their respective clusters.

The leaves of the hierarchy (i.e., nodes with no descendents) represent individual research projects [PSLC members: Should these nodes be studies instead of projects?]. Each is maintained by its project’s leader.

Between the cluster nodes and the leaves, there may be some intervening nodes. For instance, if a group of Coordinative Learning studies all address a similar research question (e.g., how to use verbal and visual instruction together effectively), then a node may be created to summarize their shared aspects. Its parent is the Coordinative Learning cluster node, and its descendents are the relevant project nodes. These sub-cluster nodes are maintained by the cluster members.

At present, the hierarchy is a tree. That is, every node has at most one parent. If this parsimonious structure impedes theoretical development, we may relax the restriction and allow nodes to have multiple parents.