Extract from Blackwell, A.F. (1998).
Metaphor in Diagrams
Unpublished PhD Thesis, University of Cambridge.
These paradigms change the very way you think. They lead to new habits and models of behaviour that are more powerful and productive. They can lead to a human-machine synergism.
Smith, Irby, Kimbal, Verplank & Harslem
(1982), p. 272.
As described in chapter 2, a class of diagrammatic tools which support particularly complex problem solving is the class of visual programming languages (VPLs). VPLs are also unusual in that they have a relatively recent history compared to other types of diagram, and it is therefore possible to investigate the reasons why they have been developed and promoted. Green, with various collaborators, has made many empirical studies of VPL use. This empirical approach to comparing the relative advantages of different programming languages can be contrasted with superlativist claims for the superiority of VPLs (Green, Petre & Bellamy 1991). Several studies have supported Green's contention that superlativism is unjustified - the empirical evidence is reviewed by Whitley (1997), and dates back to comparisons finding no difference in performance between flowchart users and those writing plans in English (Soloway, Bonar & Ehrlich 1983).
Despite the paucity of empirical evidence, and the availability of analytic tools such as Green's Cognitive Dimensions, superlativism has been widespread in VPL research. At one level, superlativist claims might appear ridiculous, as though someone were advocating the replacement of written language with images (Dondis 1973, Barker & Manji 1989). In fact, some researchers candidly acknowledge the lack of empirical evidence for the benefits of their work, and suggest that novelty is sufficient justification for new notations to be developed (e.g. Hyrskykari 1993). Other developers of VPLs report negative findings after empirical evaluations of their own projects, but this is seldom regarded as a reason to abandon the project (e.g. Ladret & Rueher 1991, Grant in press). It is far more common, however, to expend considerable effort on designing graphical alternatives to existing textual notations without ever questioning why the textual notations are inadequate (e.g. Missikoff & Pizzicanella 1996).
This chapter does not evaluate the empirical evidence for and against visual languages, nor the theoretical considerations that cause an information structure to be well suited to a particular task. Instead, it investigates the metacognitive assumptions that underlie the superlativist claims made in VPL research. Those assumptions are generally based on the beliefs that VPL researchers hold about the nature of problem-solving and programming, and about the nature and uses of diagrams. These metacognitive beliefs - beliefs about the nature of our own thought processes (Flavell 1979) - are important for several reasons. Firstly, metacognitive beliefs can have significant effects on the way that people choose cognitive tools. For example, many people believe that hiding an object in an unusual place will make it easier to remember. This particular metacognitive belief is unfounded (Winograd & Soloway 1986), a fact which is useful to know when planning one's household affairs.
Secondly, the metacognitive beliefs of VPL designers influence the choices that they make when designing new languages, and hence affect the characteristics of the languages themselves. These beliefs may not be questioned where they are in accordance with popular introspection, as observed by Meyer (1997) in his reanalysis of Washburne's classic study of graphs. Thirdly, metacognitive beliefs influence the strategies that people use when solving problems using diagrams (Schoenfeld 1983). Users of a VPL will similarly use the tool in ways determined by their own beliefs about the value of diagrams. Unfortunately, metacognition is not always an accurate guide for performance in comprehension and problem-solving: Glenberg, Wilkinson and Epstein (1982) found that 92% of experimental subjects were certain they had understood a passage that was actually self-contradictory, while Metcalfe and Wiebe (1987) found that success in solving insight problems was unrelated to subjects' expectations of their performance. This chapter presents three studies of metacognitive beliefs. All three survey the opinions of experts regarding the cognitive advantages of VPLs, but the three survey populations have very different experiences of visual programming. The first survey investigates the metacognitive beliefs of VPL researchers, as published in the visual programming research literature. The second compares the opinions of experienced programmers who had not used a visual programming language. The third investigates the opinions of programmers who are experienced users of a commercially available VPL.
This first study investigates the systematic nature of metacognitive beliefs among VPL researchers. Other fields of computer science exaggerate the intuitiveness of the innovations they introduce, but the underlying assumption is often a straightforward simplification (such as the contention that an "object" in object-oriented programming is as easy to identify and manipulate as an object in the real world - Blackwell 1993). A corresponding simplification in VPL research (as in research into diagrams and illustration) might be an appeal to the 1920s marketing slogan, now would-be Chinese proverb "a picture is worth a thousand words" (Mieder 1990, Blackwell 1997a). The justification for VPL research is seldom so simple, however. This study investigates the range of statements that have been made by VPL researchers.
The results of this study have previously been published in Blackwell (1996b).
The main source of data for this survey was a two-volume collection of well-known papers in visual language research, published by the IEEE (Glinert, Ed. 1990a, 1990b). This was supplemented by several textbooks on visual programming languages (Shu 1988b, Chang, Ed. 1990a, 1990b, Burnett, Goldberg & Lewis, Eds. 1995), by two volumes of the Journal of Visual Languages and Computing, and by a search for visual programming articles in two popular computer science journals (Communications of the ACM and IEEE Software) over the period after the publication of the Glinert collection. Approximately 140 publications were considered in all. The original publication dates ranged from 1977 to 1995, with a median year of 1988.
The first stage in data collection involved the identification of passages in these papers where the research was justified, or the significance of the results discussed, in terms not directly derived from the technology described. These passages generally appeared in either the introduction or the concluding sections of the paper. A statement such as "visual programming languages will result in improved productivity because the human mind is optimised for vision" (not an actual quote from the study) would be a typical target for analysis.
Once these passages had been collected, they were divided into individual phrases, and each phrase was classified according to the theme that it addressed. This segmentation and classification was repeated at two different stages of the research. The initial classification (described in Blackwell 1996b) considered only the material collected in the current survey (i.e. it did not include distinctions discovered during the analysis of surveys 2 and 3), and was not based on any external reference point. The second classification considered material collected in all three of the surveys that are described in this chapter, and provided a common coding framework for all three sets of data. It is the later of the two classifications that is described here. An analysis based on this second classification has been published previously by Whitley and Blackwell (1997).
The classification framework was based on an initial sample (20%) of the material from all three surveys, which was considered by two coders - coding decisions regarding this sample were discussed at length, in order to clarify the interpretation of each theme. A separate sample was used to assess inter-rater reliability at the end of the third survey. The theoretical motivation for the framework was mixed, addressing relatively independent research questions arising from the respective projects of Whitley and myself. Nevertheless, each phrase in the survey material was allocated uniquely to one theme in the classification framework. The allocation of phrases to independent research questions is most relevant in survey 3, and is discussed further there.
40 passages describing metacognitive beliefs were identified in the corpus of 140 research publications surveyed. In the following summary of the themes that were addressed, publications are identified by an index number. The actual publications are listed in table 3.1, with page numbers identifying the locations of those passages which were found within longer texts - full citations can be found in the bibliography.
1 |
Baroth & Hartsough (1995), p.22 |
21 |
Gutfreund (1987) |
2 |
Brown & Sedgewick (1984), p.178 |
22 |
Huang (1990), p.68 |
3 |
Burnett & Ambler (1994) |
23 |
Ichikawa & Hirakawa (1987) |
4 |
Burnett, Baker, et. al. (1995) |
24 |
Karsai (1995) |
5 |
Chang, Ungar & Smith (1995), p.186 |
25 |
Kimura, Apte, et. al. (1995) |
6 |
Chang (1987) |
26 |
Kopache & Glinert (1988) |
7 |
Chang, Costagliola et. al. (1995) |
27 |
Lodding (1983) |
8 |
Chang. (1990), p.2 |
28 |
Lord (1994) |
9 |
Costagliola et. al. (1995) |
29 |
Myers (1986), pp.59-66 |
10 |
Cox (1986), p.158 |
30 |
Pong & Ng (1983) |
11 |
Cox & Pietrzykowski (1988) |
31 |
Repenning & Sumner (1995) |
12 |
Diaz-Herrera & Flude (1980) |
32 |
Schiffer & Fröhlich (1995), p.201 |
13 |
Dillon, Kutty et. al. (1994) |
33 |
Shu (1986) |
14 |
Duisberg (1988) |
34 |
Shu (1988a), p.662 |
15 |
Edel (1986) |
35 |
Shu (1988b), pp.1,6 |
16 |
Ford & Tallis (1993) |
36 |
Smith (1977) |
17 |
Glinert & Gonczarowski (1987) |
37 |
Tanimoto & Glinert (1986), p.54 |
18 |
Glinert & Tanimoto (1984) |
38 |
Tripp (1988) |
19 |
Glinert (1990), pp. 145, 148,170 |
39 |
Wood & Wood (1987) |
20 |
Goldberg, Burnett & Lewis (1995), p.11 |
40 |
Yeung (1988) |