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Anais do IHC'2001 - Departamento de Informática e Estatística - UFSC

Anais do IHC'2001 - Departamento de Informática e Estatística - UFSC

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<strong>Anais</strong> <strong>do</strong> IHC’2001 - IV Workshop sobre Fatores Humanos em Sistemas Computacionais 237<br />

construction of the diagram [Wang et al., 1995]. A closer examination of Figure 4 might<br />

give elements to support the interpretation that some H are A, which is not a valid logic<br />

conclusion. An attempt to correct this representation by removing the intersection between<br />

circle H and circle A, as shown in Figure 5, would also lead to interpretations that are<br />

logically incorrect (i.e. that no A is H).<br />

Figure 5: An alternative representation for “all humans are breast-fed and some<br />

animals are not breast-fed; therefore some animals are not human”<br />

This situation has motivated research in different directions. Wang et al. (1995) have<br />

proposed a series of rules and constraints for constructing good diagrammatic<br />

representations. Stenning and In<strong>de</strong>r (1995) and Stenning and Oberlan<strong>de</strong>r (1995) have<br />

chosen another path and explored mo<strong>de</strong>s, media, and expressiveness of representation<br />

systems. The latter have proposed a hierarchy of representation systems (minimal<br />

abstraction systems, limited abstraction systems, and unlimited abstraction systems) and<br />

have provi<strong>de</strong>d experimental cognitive evi<strong>de</strong>nce that limited abstraction representation<br />

systems (LARS), which allow for representing in<strong>de</strong>terminacy are better as cognitive<br />

scaffolding in learning than minimal (MARS) and unlimited abstraction representation<br />

systems (UARS). It is interesting to notice that the problem with either Figures 4 or 5 is<br />

their excessive <strong>de</strong>gree of (emergent) <strong>de</strong>termination with respect to the relation between H<br />

and A.<br />

Stenning and In<strong>de</strong>r (1995) have also analyzed matrices and tables as graphic<br />

representations. They have conclu<strong>de</strong>d that these kinds of visual aids can only represent data<br />

that is fully specified on the dimensions present in the matrix. Partially <strong>de</strong>termined data<br />

cannot be represented, for the assignment of data to a cell automatically specifies its value<br />

in all of the table’s dimensions. This observation has an interesting consequence for<br />

teaching Men<strong>de</strong>l’s laws of heredity with the use of Punnet Squares (see Figure 6).<br />

If we take the Law of Dominance, for example, we can use the Punnet Square to represent<br />

the principle that “when crossing parents with pure contrasting heredity traits, the next<br />

generation of individuals will exhibit the characteristic of only one of the contrasting<br />

traits”. The Punnet Square is a matrix (a table) where the traits of the female and male<br />

parents are displayed in the first column and first row. The possibilities of genetic<br />

combinations are displayed in the cells of the table, by the concatenation of co<strong>de</strong>s used to<br />

represent each heredity trait. Figure 6 shows a Punnet Square for the crossing of two pure<br />

types: tall-stem pea (TT) and a short-stem pea (tt). The principle is represented by the fact<br />

that all genetic combinations of the offspring are Tt. Observably, this corresponds to the<br />

fact that the individuals show the characteristics of trait ‘T’, <strong>de</strong>spite the presence of trait ‘t’<br />

in their chromosomes.<br />

T T<br />

t Tt Tt<br />

t Tt Tt<br />

Figure 6: The Punnet Square representing Men<strong>de</strong>l’s Law of Dominance

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