DEFINICIONES DE TÉRMINOS BÁSICOS

Now, if we, as designers, are able to conceive of a representation of a conceptual model of the system that at the pragmatic level reflects the way in which an expert would approach the problem at an operational level, we are likely going to maximize compatibility (i.e., the way in which a system responds to users’ expectations (Buxton, 2007a)) and, in turn, users’ perfor- mance. In other words, we can facilitate the dialogue between a user and the system by creating affordances which are coherent and consistent with users’ set of skills, thus in turn shaping users’ mental model of the system.

As suggested by Buxton (1994), the motor, cognitive, as well as social skills which we have acquired in the experience with physical reality provide us with a reach material for skill transfer in the design of hybrid interactions. To this end, we clearly need to investigate how chunks of actions can be represented and supported by the interface, at the pragmatic level. The use of interaction metaphors which go beyond the design of visual cues for mouse and keyboard input constitutes an interesting approach in this respect.

2.6

Interaction Metaphors

Metaphors were already used in written languages in early writings, as in Sumerian epics. Throughout history, the concept of metaphors has been developed in different fields, especially in philosophy, literature, cognitive linguistics and interaction design, with mutual influences among the fields. In cognitive theories, metaphors are presented in the form of “A is B”, where B is said to be the source (orvehicle) and A is the target (ortenor). Generally, the source metaphor is determined based on the common knowledge in the real world and the target is the complex entity (often an abstract concept) that should be represented. In Black’s interaction theory of metaphor (Black, 1972), a metaphor is not simply a process of transferring properties from the source to the target, but a complex interaction between them, in which our knowledge of the target is equally across the target and the source. Thus, the properties that are highlighted by the comparison are determined by the interaction of the tenor and the vehicle.

Such a theory has had most influence on the following cognitive linguis- tics theories. Lakoff and Johnson’s (1983) work Metaphors We Live By is the most popular example in this area. Their main account is that a large part of the human conceptual system is metaphorical itself. Thus, metaphors are not just constructs of a language, but they rather constitute some funda- mental tools for human reasoning and understanding. Metaphors underly our reasoning structure and can shape our perceptions and actions by creating relationships between what we know about our physical and social experience

2 Underlying Concepts

and other topics. In this sense, the authors argue against the idea of a priori objective similarities: Metaphors do not just point out existing similarities, but rather create them.

From these ideas, both metaphorical as well as anti-metaphorical ap- proaches to interaction design have generated. On the one hand, metaphors have been recognized to play an important role in user interface design as descriptions and representations of conceptual models, e.g. (Carroll and Thomas, 1982), (Madsen, 1994), (Laurel, 1986), (Marcus, 1998), and even as essential tools for design thinking (Erickson, 1995). From these views, they can serve as means for making an unknown complexity into an understand- able format as they provide an intuition of how things work, transferring the world knowledge.

On the other hand, the lack of a priori, objective similarities implies in- terpretation, which is subjective. This has motivated the skepticism of other approaches towards the value of metaphors: Users’ cultural differences, their different experience and levels of skill, as well as metaphors’ scalability and coherency, are some of the main concerns of these accounts, e.g. (Richard- son, 1993) and (Nelson, 1990). According to Halasz and Moran (1982), for example, the use of metaphors is limiting and inappropriate to teach new users how to interact with computing systems. These, indeed, have a syn- tactical complexity which cannot be efficiently learned and understood by analogy. Rather, the authors propose the use of abstract conceptual models for teaching users how to reason about the system.

Another thesis considering the relationship between metaphors and learn- ing is the one presented by Cooper and Reimann (2003). From the authors’ perspective, most elements of intuitive Graphical User Interfaces are actu- allyidiomatic. Idiomatic interfaces are based on the learning of simple, non- metaphorical and behavioral idioms (i.e., principles) to accomplish goals and tasks. Intuition, on the other hand, is a mental comparison between a new experience and things we have already learned. For Cooper and Reimann, “windows, title bars, close boxes, [...] are things we learn idiomatically rather than intuit metaphorically”.

The point here is to recognize that a large part of idioms are actually what, in linguistic terms, one would call dead metaphors. These are metaphors which have been so much embedded in a culture or a language, that their sense of a transferred image has become unnoticed. A curious observation is that several dead metaphors are actually embodying a physical action as a source of transition (em-bodiment and under-standing are metaphors themselves). In this sense, it becomes artificial to some extent to draw a hard line between metaphorical intuition and idiomatic learning. One could argue, indeed, that the learning activity is in large part metaphorical itself, as

2.6. Interaction Metaphors

we relate new concepts to other knowledge we already have (which is often implicit knowledge, that comes from our physical experience) in order to reason and create meaning in a semantics, i.e., in a language. The difference, rather, relies in the granularity of the analysis, i.e., whether we consider the chunks (the parts that constitute the metaphors) or the idioms (the phrases consisting of chunks). In other words, it makes a difference whether we just consider metaphors which directly emulate the source entity into the target domain, vs. lateral metaphors which transfer an aspect (e.g., a physical gesture) from a domain to another one to convey new meaning.

In this sense, despite their limitations, we can consider the PC desktop metaphor and the direct manipulation paradigm as successful examples of transferring knowledge and gestures (e.g., the tension in dragging an object from a location to another one) from the physical world into the digital one, thus representing the complex command-line structure of computing systems into a more accessible format. The next section introduces these concepts.

2.6.1

The Desktop Metaphor

The computing domain has been characterized by the nearly universal ac- ceptance of the desktop metaphor for decades. In 1981, the Xerox Star workstation set the stage for the first generation of Graphical User Interfaces (Smith et al., 1982), establishing a metaphor which simulates a desktop on a bit-mapped screen and is operable with mouse and keyboard. The Star also set several important HCI design principles, such asseeing and pointing vs. remembering and typing, and what you see is what you get. The Apple Macintosh brought this new style of interaction into the public’s attention in 1984 (Williams, 1984), creating a new trend in the PC industry which was further widespread through the large diffusion of Microsoft Windows.

Although this was a fundamental contribution to the enhancement of human-computer interaction, the limited vocabulary of the pragmatic level has somewhat restricted the semantics of interaction with digital media. The emerging scenarios of ubiquitous computing drive the design of alternative computing tools and novel usage paradigms encompassing multi-user and multi-display environments, as well as multiple input/output modalities. In this respect, one can expect that the concept of direct manipulation - which has been the basis of the desktop metaphor and the WIMP paradigm - will evolve, as novel technological possibilities for direct input interfaces become available. The principles of direct manipulation are explained below.

2 Underlying Concepts

2.6.2

Direct Manipulation

In the Personal Computer environment, direct manipulation describes the activity of manipulating objects and navigating through virtual spaces by exploiting users’ knowledge of how they do this in the physical world (Shnei- derman, 1987). The three main principles of direct manipulation are:

• continuous representation of the objects and actions of interest;

• physical actions or presses of labeled buttons instead of complex syntax;

• rapid incremental and reversible operations whose effect on the object of interest is immediately visible.

Direct manipulation is the basis for the dominant WIMP paradigm, with which we manage different applications. According to the activities they support, applications rely on different metaphors. In the Microsoft Office software package, for instance, visual and auditory icons mimic the objects of a real physical office. In software programs for graphic design, icons re- semble brushes and pencils. While the metaphor varies according to the application domain, the general paradigm does not change as the appear- ance of widgets for desktop GUIs remains consistent. Graphic elements are mapped to objects of the real world and those in turn provide affordances for mouse and keyboard interaction, e.g. 3D effects for clicking buttons, white fields for text entry, and ripples on the moving part of scrollbars for dragging (cf. Chapter 1, Fig. 1.1).

Despite talking about direct manipulation, in the Desktop environment we mostly need indirect input devices, such as mice, track pads or joy-sticks, to interact with the system. As interactive environments become more com- plex, encountering a variety of displays, both physical and digital, as well as a diversity of input and output modalities, novel affordances for the manip- ulation of information need to be designed and encoded.