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238                         Adaptation

                 Table 7.2.  Summary of the initial HS model of children’s counting skill.

            Ontology
            Entities: X, Y, Z, …, of types object, number, set
            Objects: O 1 , O 2 , O 3 , …
            Numbers: N = 1, 2, 3, …
            Sets: {O i }, i = 1, 2, 3, …
            Properties: first(X), current(X), origin(X)
            Relations: associate(N, O), member(O i , {O}), successor(N, M), after(O j , O i )
            Counting tasks: count({O})
            Answers to counting tasks: answer(N, count({O}))
            Actions and operators
            FirstObject (O) ==> first(O)
            NextObject(O i , O j ) ==> after(O j , O i )
            FirstNumber (N) ==> first(N)
            NextNumber(N, M) ==> after(M, N)
            AssNumObj(N, O) ==> ass(N, O)
            Answer(N, count({O})) ==> answer(N, count({O}))
            Initial, overly general skill:
            R1: count({O}) object(O i ) ===> FirstObject(O i )
            R2: count({O}) current(O i ), object(O j ) ===> NextObject(O j , O i )
            R3: count({O}) number(N) ===> FirstNumber(N)
            R4: count({O}) current(N) number(M) ===> NextNumber(M, N)
            R5: count({O}) current(N) current(O) ===> AssNumObj(N, O)
            R6: count({O}) current(N) ===> Answer(N, count({O}))
            Based on Ohlsson and Rees, 1991a, Tables 2 and 3.



            case of skill acquisition for which there are strong empirical reasons to believe
            that there is a prior declarative knowledge base. Children can learn to count
            with minimal and haphazard instruction because they have prior knowledge
            of a small set of counting principles that constrains counting behavior.
               HS can duplicate the acquisition of this skill, given the same knowledge
            that children start out with.  HS was programmed with the basic competence
                                  46
            of pointing to objects and saying numbers. In addition, we gave HS the actions
            that are specific to the counting domain, primarily to select an object, point to
            an object, retrieve a number, speak a number and declare the answer. HS was
            given an initial competence that consisted of six rules, one to control the appli-
            cation of each of the six key cognitive operations; see Table 7.2. These rules
            were overly general and hence error prone. The prior declarative knowledge
            consisted of constraints that represented a version of the Gelman and Gallistel
            counting principles. The five constraints are stated conceptually in Table 7.3.
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