Abstract:Research conducted on the theory of selective attention suggests that varying the graphic combinations used when designing bivariate symbols affects the functionality of the symbol. Some graphic combinations appear to facilitate the ability to visualize correlation between the data sets represented by the symbol; others appear to be more effective at representing the data sets individually, some even at the expense of extracting correlational information. The purpose of the research described here was to test the strength of these findings in a map use context. Several bivariate symbol designs were tested using map use tasks designed to test participants' abilities to extract either correlational or individual information. Participant reaction times provided an assessment of the types and levels of interactions that occurred with each symbol set, Results corroborate previous research in both cartography and psychology, with several symbol designs falling into each of three interactional categories: separable, integral, and configural. By confirming and expanding previous research, this study provides further evidence of the strength of selective attention theory in aiding the design of bivariate thematic maps.

The purpose of this research was to empirically assess perceptual groupings of various combinations of symbol dimensions (e.g., graphic variables) used in designing bivariate map symbols. Perceptual grouping ability was assessed using the theory of selective attention, a construct first proposed in psychological research. Selective attention theory contends that one's ability to analyze a symbol's dimensions-such as color or size-is affected by other dimensions present in the same symbol. Symbol dimensions are described as either separable (capable of being attended to independently of other dimensions), integral (cannot be processed without interference from other dimensions), or configural (i.e., show characteristics of both integrality and separability, which may also form new, emergent properties). Without empirical evidence describing such interactions for various combinations of symbol dimensions, cartographers cannot truly evaluate the functionality of the symbols they use on maps. The symbol dimensions or graphic combinations chosen for this study were selected to incorporate a wide range of traditional cartographic symbolization, including line and lettering symbolization, areal shading, dot patterns, and point symbols. Combinations were examined in an abstract setting using a speeded classification task, which is the traditional means of studying selective attention. Subject reaction times provided an assessment of the levels of integrality, separability, and configurality. Results suggest that most symbol dimension combinations are either separable or exhibit evidence of asymmetrical dimensional interactions. Findings from this study will be integrated into subsequent experiments, the results of which will assist cartographers in the design of complex map symbols.Article:

Abstract:Several techniques have been proposed for displaying data certainty on maps, but few have been empirically tested for effectiveness. While it is important to make data certainty information easily accessible, the addition of such data should not unduly increase map complexity. Thus, it becomes important for cartographers to examine the available methods for displaying this aspect of metadata and to test each for its effectiveness. The focus of this study was the display of data certainty information on graduated circle maps. Four types of accuracy indicators were evaluated for their effectiveness in communicating data certainty information. Two were traditional accuracy indicators: reliability diagrams and legend statements. Two were bivariate in form, one using a value-size combination and the other mimicking the idea of focus by varying the line value of the graduated circles to suggest a fading of symbolization for least certain data. The study was designed to assess whether subjects could identify data certainty information on test maps, and evaluate how accurately and confidently they could extract and interpret both thematic and data certainty information. Mean accuracy and confidence rates were compared for maps using different accuracy indicators to evaluate their relative effectiveness. Results suggest that subjects had most difficulty identifying and extracting data certainty information using maps that employed legend statements. They were most successful when data certainty was wedded to thematic data on the map using the bivariate accuracy indicator that mimicked the concept of focus. Identification and extraction of thematic data values were not significantly affected by choice of accuracy indicator. Article: INTRODUCTIONMap accuracy is often equated with graphic quality. As noted by both Wright (1942) and McGranaghan (1993), well-drawn, precise maps are typically taken as scientifically authentic, regardless of the quality of their underlying data. Aesthetically pleasing maps, however, can conceal problems with the data and methods used in their creation. Wright (1942:527) provides perhaps the most interesting analogy on this subject: "A map may be like a person who talks clearly and convincingly on a subject of which his knowledge is imperfect." Always a problem cartographically, this particular issue has become even thornier as we have moved from manual, hand-drawn maps into the digital environment where nearly anyone who can master a software package can be a "mapmaker". Technology provides us with amazing capabilities in creating, editing, and displaying spatial data, capabilities that are offset by the fact that many of these maps are inappropriately used given the data upon which they are based. Since the validity of the underlying data is the key to making credible decisions, it makes sense that reporting and spatially depicting data certainty information should be addressed in a contemporary cartographic framework. Yet, as MacEachren (1994:67) points out: "The cartographic litera...

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Abstract:The research discussed in this paper applies the theory of selective attention to graphic variables used in designing map symbols. Selective attention contends that our ability to analyze a symbols graphic variables (i.e., color, size) is affected by other graphic variables present in the same symbol. Psychological research suggests that certain combinations of graphic variables can enhance or restrict selective attention. In this literature, variables are described as either separable (capable of being attended to independently of other dimensions), integral (cannot be processed without interference from other dimensions), or configural (shows characteristics of both integrality and separability and may also form new, emergent properties). For example, sometimes it may be desirable for a map user to focus individually on separate symbol dimensions when using a bivariate or multivariate map, whereas under other conditions it may be advantageous for him/her to integrate the graphic variables visually for interpretation. Without empirical evidence describing such interactions for various combinations of graphic variables, cartographers cannot truly evaluate the functionality of the symbols they use on maps. The research reported here is the result of the first of a set of four inter-related experiments. Combinations of graphic variables were examined in an abstract setting using a speeded-classification task. Response data and accuracy data were used to provide an initial assessment of the levels of integrality, separability and configurality of several graphic combinations. Findings from this study will be integrated into subsequent map-using experiments, the results of which will assist cartographers in the design of complex map symbols.