1. Introduction
As visual means of communication, maps allow sharing information, ideas, and thoughts and enable us to relate to spatial phenomena from a viewpoint beyond direct experience. Maps allow us to communicate and think about the near and the distant, about phenomena, events, and objects that “are not tied to the immediate present” [
1] (p. 1). Likewise to any other form of communication, maps are
representations of such near or distant phenomena but are not the phenomenon itself. As words describe or express, maps depict and express [
2]. Both words and maps may refer to a particular idea or phenomenon, yet they are not the idea or phenomenon itself [
3].
When we look at maps, “we see symbols spread out on the space of a document, on paper or a computer screen”, and we expect the symbols to be related to geospatial objects or phenomena [
4] (p. 21). Maps are a means of conceiving, articulating, and structuring the human world [
5]. By applying a mutually shared set of signs and semiotic rules, sheer unlimited, meaningful, novel messages about space and time can be communicated through maps. It is, however, the depicted as much as the un-depicted, the said as much as the un-said, which will influence people’s perception, interpretation, and imagination. The process of map making is based on a variety of such decisions, such as regarding which information to depict as well as how to depict it. "There is nothing natural about a map. It’s a cultural artifact, an accumulation of choices made among choices every one of which reveals a value: not the world, but a slice of a piece of the world; not nature but a slant on it; not innocent, but loaded with intentions and purposes; not directly, but through a glass; not straight, but mediated by words and other signs" [
6] (p. 78). Hence, maps are never neutral but based on a myriad of choices of
what to communicate and
how to communicate.
To this day, the cartographer faces the challenge, as well as the pleasure, of near infinite variations of visual variables to choose from. Yet, which ones are most suitable for a given context, for a given type of spatial information, object, or phenomenon? The variety of methods available to represent information through maps allows for strikingly different results [
7], while the choices of how we communicate spatial information will affect how people respond to it. In other words, cartographic design decisions will influence the perception and interpretation of maps [
8]. In as far as cartographic semiology provides a theoretical framework in geospatial communication by addressing the denoting qualities of visual variables [
9], it does not encompass their connotative effects on human affect, perception, and cognition.
Between the intersection of psychology, cartography, and semiotics, this research drew attention to the connotative, affective qualities of shape symbols in cartographic communication. Shapes are considered as core elements in visual communication over a wide range of disciplines [
9,
10,
11]. In cartography, shape symbols are prevalently used to depict and geo-reference spatiotemporal phenomena, objects, and events. To establish a profound theoretical reference for this research, this paper, first, outlines central semiotic traditions and perspectives on the dimensions and relations of signs (see
Section 2). This paper further reports on empirical studies, which were conducted to assess and compare affective qualities of symmetric and asymmetric shape stimuli in cartographic and non-cartographic contexts (see
Section 3 and
Section 4). Findings and implications for future research are discussed in detail in
Section 5 and
Section 6.
2. Theoretical Background
Cartography as a science of human communication is concerned with establishing a mutually shared set of cartographic signs and semiotic rules. In the history of semiotics, two traditions have evolved which study communication either as dyadic or triadic processes. Both approaches emphasize that “the sign is more than its constituent sign vehicle” [
12] (p. 79). Dyadic semiotic theorists, such as Saussure, consider the sign as a conceptual object, which consists of an expression (i.e., a
signifier) and the concept the expression refers to (i.e., the
signified) [
12] (p. 88 for a synopsis). Triadic models, on the other hand, emphasize that “something is a sign only because it is interpreted as a sign of something by some interpreter” [
13] (p. 4). Triadic theorists, such as Plato, Aristotle, or later Morris and Peirce, emphasized three semiotic dimensions, i.e., the
sign-vehicle which acts as a physical sign (i.e., expression or carrier of meaning, such as a sound, mark, or movement), the
referent (i.e., the phenomenon or object of reference the sign-vehicle refers to), and the
interpretant (i.e., the sign’s effect on the interpreter, such as the meaning or concept the sign-vehicle refers to for the interpreter) [
12] (p. 90 for a synopsis).
The perspective of semiotics as a two- or three-dimensional process enables theorists to consider communication through signs as a complex, interrelated process. Triadic models, for example, allow us to distinguish between three dyadic semiotic relations, i.e., those of
syntactics, which Morris refers to as the rule-based relation between signs;
semantics, which refers to the relation between sign-vehicle and referent; and
pragmatics, which refers to the relation between sign-vehicle and interpretant or concept [
14]. The triadic structure further prompts semioticians and cartographic theorists to consider the model’s triangular relations, such as by considering each of the three sign components as possible mediators of sign communication (see
Figure 1) [
12,
15].
The interpretant as mediator in the semiotic triangle is regarded as a standard approach, stemming from “Aristotle’s definition of words as signs of the soul, and the latter as likenesses of actual things” [
12] (p. 89). In this understanding, sign-vehicle and referent are mediated by their interpretant (i.e., sense or meaning), either as a sign-vehicle–interpretant–referent relation or as a referent–interpretant–sign-vehicle relation, in which a thing (i.e., referent) may evoke an idea (i.e., interpretant), which creates a word or symbol (i.e., sign-vehicle) (see
Figure 1a). From the perspective of
the referent as mediator (see
Figure 1b), the referent (e.g., object) “is a phenomenon of secondness, and the interpretant is one of thirdness” [
12] (p. 89). The third perspective considers
the sign-vehicle as mediator (see
Figure 1c), as a “link between thing and meaning” [
15] (p. 246), where something becomes a sign-vehicle of a referent when it gives rise to the idea or thought of that referent [
16]. Nöth refers to this process as “meaning endowing act”, where sense (i.e., the interpretant) leads to sign production (i.e., sign-vehicle), which refers to an object (i.e., referent) [
12] (p. 90).
Cartographic research on semiotics, which focuses on
the interpretant as mediator, emphasize the role of a mutually shared set of codes established between the cartographer and the percipient, by which a sign-vehicle is linked to its referent [
15], such as by specifying the syntactic relationship between graphic variables and their referents [
9]. From the perspective of
the referent as a mediator, attention is drawn to the categorizations of referents, which cartographic sign-vehicles refer to [
15], such as the differentiation of geographic versus nongeographic information, spatial versus spatiotemporal dimensionalities, discrete versus continuous phenomena. Cartographic research may also refer to the
sign-vehicle as mediator, where something which is not the referent becomes a sign-vehicle of that referent (such as map symbols become sign-vehicles), and as such, mediating between referent and its associated concept or meaning [
15]. As mediators between things and meaning, sign-vehicles give rise to an idea or thought of a referent. While both sign-vehicle and referent may be of a physical nature, meanings are mental events and difficult to clearly define [
12,
16]. The measurement of meaning is, therefore, considered a challenging task. Morris, for example, did not include the concept of meaning in his semiotic theory due to its imprecision, proposing “to introduce special terms for the various factors which ‘meaning´ fails to discriminate” [
14] (p. 19). Later, theorists have been attempting to decompose the “many meanings of ‘meaning’” [
16] (p. 2), often relating their findings to two core dimensions, i.e., the
dimension of sense and
the dimension of reference [
12] (p. 94 for a terminological synopsis). On the dimension of reference, all cartographic sign-vehicles, such as map symbols, can be considered as identifiers which either apprise, inform, state, designate, indicate, or label. Some map signs, however, may also have a stimulating character, may prescribe, express, or connote [
15,
17]. These qualities refer to the dimension of sense. The two dimensions or functions of sign-vehicles may also be regarded as representational versus expressive [
14,
17], as apprising versus stimulating [
6], as denotative versus connotative [
12]. Most cartographic semiotic research on sign-vehicles has focused on the denoting qualities of map signs, attempting to specify explicit properties and attributes to identify optimal characteristics of sign-vehicles (such as symbol size, color hue, etc.) [
6,
15]. Yet, map signs may not only depict and denote but also express and connote [
2]. These connotative qualities can be as powerful as to modulate affective responses and cognitive processes, such as influencing learning, memory, attention, and decision making, as related research shows [
18,
19,
20].
In the 1950s the psychologists Osgood et al. developed the
Semantic Differential to measure such connotative qualities [
16]. The semantic differential technique is based on the premise that any concept (be it a painting, a person, a word, an abstraction, etc.) can be defined or described by its connotative meaning. The technique combines association and scaling procedures, designed to “give an objective measure of the connotative meaning of concepts” [
21] (p. 579). It is based on the attempt to subject meaning to quantitative measurement and allows comparing different stimuli in the same semantic space. Factor analysis usually reveals two or three semantic dimensions of connotative meaning, i.e.,
valence (evaluation),
arousal (activity), and, at times,
dominance (potency) [
16,
18,
22,
23,
24,
25]. It is assumed that whenever humans perceive themselves, other persons, events, or any attitude object, the most relevant discriminations are made in terms of these two or three
affective dimensions.
As such, affect is considered a psychological primitive [
18,
26], with some affective response always present within a person [
27]. Affect can be neutral, moderate, or extreme [
27]. When affect is moderate or extreme, it can be consciously experienced as pleasant or unpleasant and form the basis of an emotional experience [
27,
28]. When affect is neutral, it influences conscious experience and behavior more mildly and is rather experienced as
affective qualities, i.e., as attributes or properties in the surroundings, of stimuli, objects, or events [
24,
25]. Affective qualities are commonly described by affect-denoting adjectives such as pleasant, unpleasant, exciting, boring, safe, upsetting, soothing, etc. Likewise to human communication, where one cannot communicate without expressing some level of affective state [
18], objects and events all imbue affective qualities [
27]. Perceiving and evaluating the affective qualities of the human environment and the stimuli therein, can, therefore, be considered a fundamental aspect of human information processing [
27] which has “psychological consequences that reach far beyond the boundaries of emotion”, influencing decision making and human behavior [
18] (p. 167).
Recent approaches in cartography have started to emphasize the role of affect in respect to maps [
29]. While some attempts aim to represent affective responses of people by the means of maps [
30], other approaches use maps as a means to collect people’s affective responses in different environments [
31]. The third strand of affect research in cartography draws attention to the role of maps as triggers of affective responses. The latter attempt strives to disclose how cartographic design, in other words,
the map as sign-vehicle, will influence affective responses and related judgments. Recent research strongly supports this notion. Empirical studies show that a change in aesthetic map style [
32,
33] or visual rhetoric style [
34,
35] will influence people’s affective and cognitive judgments, trust, and recall. Research, which systematically studied map symbolization, further suggests that altering particular cartographic variables, such as line symbols or point symbols, will affect map preferences and people’s accuracy of judgments [
36] as well as influencing detection speed in visual search tasks [
37]. Another crucial factor in visual communication is to accord the map symbol with the information it aims to represent. Research stresses that, besides the variety of means to visualize geospatial information, only a few of those are suitable and effective for a given content and lead to accurate judgments about the depicted phenomenon [
38,
39,
40,
41]. Supposedly simple changes in the style of sign-vehicles can lead to substantially different connotations [
42].
Empirical research on the connotative meaning of map signs is, yet, still scarce. Semiotic differentiations are often neglected in cartographic research and applications of semiotics. Keates stresses that “despite a large number of papers dealing with communication in cartography, relatively few have pursued in detail the analysis of map symbols, and the relationships between map symbols and semiotic theory” [
17] (p. 179). Consequently, “the difference of what a map sign means and what it represents has become blurred” [
15] (p. 245). There remains a need for a differentiated understanding of how visual variables can be used to encode information [
38]. The present research, therefore, draws attention to the connotative qualities of map signs, and, in particular, to their role as
cartographic sign-vehicles as mediators of affective responses.
5. Discussion
As visual means of communication, maps enable us to relate to geospatial phenomena and events from a viewpoint beyond direct experience. As such, maps support us to communicate, to think about, and to imagine the near and the distant. As representations, maps depict and express spatial phenomena but are not the phenomenon itself. Likewise, the visual variables employed in maps, such as map signs and symbols, are abstractions and generalizations, which give rise to an idea or thought of their referents.
While map signs can be considered as identifiers which aim to denote and inform about spatial phenomena, objects, and ideas, related research stresses that signs and symbols imbue connotative qualities which modulate cognitive processes, such as learning, memory, and attention [
19,
20,
28]. Semiotic research in cartography has largely been concerned with the denoting qualities of map signs, by taking into account human perception and cognition to specify characteristics and attributes of visual variables (such as symbols’ size, color hue, etc.). The present research, however, focused on the connotative character of map symbols, by assessing affective qualities of shapes. Eight shape stimuli were presented in three stimulus conditions, i.e., one stimulus set presenting shape stimuli without further context, one stimulus set displaying shapes singularly on a cartographic background, and one stimulus set displaying shapes of the same type on multiple positions on a map. With a semantic differential technique, the affective qualities of the three stimulus sets were assessed and compared within as well as between the three stimulus conditions.
The present study used a deductive approach to decide for the number of affective dimensions and items to employ in a Semantic Differential. Literature indicates two to three affective dimensions, i.e., valence, arousal, and, at times, dominance [
16,
18,
22,
23,
24,
25]. Hence, two bipolar items for each of the three affective dimensions were selected. Based on these questionnaire items, a principal component analysis was conducted to confirm, and respectively reveal, the number of underlying dimensions tested by the Semantic Differential. The principal component analysis extracted two factors. Such a two-factor solution corresponds with the latest affect research, which emphasizes a two-dimensionality of affect [
18,
28]. In the present study, factor 1 comprised the bipolar items (harmonic, disharmonic; appealing, unappealing; calm, agitated) and factor 2 was composed of the item-pairs (weak, strong; unobtrusive, dominant; passive, dynamic). Hence, based on the bipolar items of each factor, factor 1 was labeled as
valence and factor 2 was labeled as
dominance. While the extraction of two factors corresponds to the latest theories and findings in affect and emotion research, literature moreover suggests the dimensions of
valence and
arousal as the two core components of affect. Valence usually refers to evaluative qualities, such as positive, negative, pleasant, unpleasant, appealing, unappealing, etc. Arousal refers to qualities of activation or, respectively, stillness. In the present study, however, the bipolar item calm–agitated loaded high on the dimension of valence, together with the item-pairs harmonic–disharmonic and appealing–unappealing. Given that the present empirical study was conducted in German language, this unexpected item-loading may indicate cross-cultural and linguistic differences. In the German questionnaire, the item-pair
calm–agitated translated to
“ruhend”– unruhig”. The German term
“ruhend” refers to qualities such as dormant, static, and stationary, while the term
“unruhig” refers to qualities such as restless, restive, unquiet, and agitated. The findings suggest that the item-pair
“ruhend”–“unruhig” may imbue more evaluative valence qualities in German language than their English compounds. This finding, together with results from related affect and emotion research [
19,
55], may imply the need for more language-sensitive and culture-sensitive approaches in affect research also in the field of cartography.
Based on the two factors extracted, statistical analyses within and between the three stimulus sets were performed. The overall findings strongly suggested two distinct stimuli clusters of particular affective qualities that prevailed over different stimulus conditions, i.e., a cluster of asymmetric stimuli and a cluster of symmetric, geometric stimuli. In each of the three stimulus conditions, those stimuli, which depicted asymmetric stars, scored highly negative on valence (i.e., unappealing, disharmonic, agitated) and highly positive on dominance (i.e., strong, dominant, dynamic). Stimulus material depicting symmetric shapes, on the other hand, overall, scored moderately positive on valence (i.e., appealing, harmonic, calm) and moderately negative in terms of dominance (i.e., weak, unobtrusive, passive). Among the symmetric stimuli, the circular shape, when presented singularly, was further revealed to lead to unique affective responses of high positive valence. Yet, when increasing visual complexity, such as when presenting more than one circular shape on a cartographic background, its distinct positive quality of valence decreased steadily. Such a decrease of affect intensity was also found for most of the stimuli when embedded in visually more complex, cartographic contexts. Only the star stimulus prevailed its affective valence qualities across all three stimulus conditions. In all other cases, the intensity of affect responses decreased on both affective dimensions of valence and dominance when increasing visual complexity, such as when adding a cartographic context or by increasing the number of shape stimuli on a map. This finding strongly implies that cartographic context and visual complexity will influence the degree of affective responses. At this point, it has to be stressed that the cartographic scenarios used in this research referred to simple basemaps in greyscale, yet, free from any further cartographic context, content, or task. Maps can, however, vary greatly in terms of their complexities, due to their sheer unlimited variety of information to depict, visual variables to employ, and contexts in which maps are used. It is, therefore, expected that affective responses will vary in different cartographic settings and scenarios.
Yet, despite the decrease of affect intensity due to context, the affective differentiation between symmetric and asymmetric stimuli appeared to be distinct and to prevail also in the more complex map scenarios of this research study. Empirical research from related fields further supports this notion, suggesting significant preferences for symmetry, even when symmetric shapes are of higher complexity than asymmetric ones [
56] or even when shapes are only partially symmetric [
57]. Research also shows detection time to be significantly higher in visual search tasks for asymmetric shapes (e.g., elliptic versus circular visual stimuli) [
44], again suggesting their unique visual qualities. The present empirical results add to these findings by uncovering particular affective responses towards symmetric and asymmetric shape stimuli which persist in different visual, cartographic contexts.
The overall findings led to the conclusion that shapes imbue qualities which can lead to, at times, highly distinctive affective responses. The asymmetric star stimuli, studied in this research, involved strong and most distinct affective responses, which persisted over different stimulus conditions. Hence, for cartographic communication, the findings strongly imply that asymmetric star shapes may be considered to not only denote but also to connote through qualities of negative valence and positive dominance. Map signs and symbols which are of such qualities can be considered to be more than sheer identifiers. In maps, such shape symbols may, therefore, be employed with particular care, since stimuli with strong expressive, connotative qualities may influence affective responses as well as cognitive processes and related judgments [
19,
20,
28]. Findings from this research further suggest that symmetric shapes, on the other hand, were found to be rather unobtrusive, evoking overall mild affective responses. In a cartographic context, symmetric shape symbols may, therefore, be considered as identifiers to be utilized to depict and denote.
At this point, the findings indicate that relatively simple maps can lead to distinct affective responses. As simple maps have become increasingly prevalent in our daily lives, the results indicate several practical implications. Regularly we encounter web maps in daily routines, such as when reading online news or when orienting or navigating in unfamiliar environments. The web as a new medium constrains the design of maps to the, at times very small, physical display sizes. Well-designed web maps, therefore, require extra attention and are considered as “relatively empty” [
58](p. 79). Yet, it remains an open question of how much a simple and relatively empty map can affect how we think about the information depicted, how we imagine a distant event, or how we judge a spatiotemporal phenomenon. How will expressive versus depicting map symbols influence cognitive responses, judgments, memory, and attention in more applied and in different scenarios? Which shape symbols of denoting and expressive character are most suitable for encoding which type of information? Will shape stimuli that are affectively congruent with the information or phenomenon they cartographically depict, amplify judgments of map affect, such as research showed for color congruency [
59]? And how do affective responses towards maps and map signs differ by culture, age, and user group? While the present research strongly suggests an influence of map symbols on human affect, future research is needed to tackle these open research questions and to continue exploring the possible impact of putative empty maps and innocent map symbols.