Graphical representations are often referred by eminent authors with the term visualization (or visualisation in the less diffused British version of the term).
For instance, Card et al. (1999) define the term visualisation as the use of computer-supported, interactive, visual representations of data to amplify cognition.
It has been noted by Spence (2001) that there is a diversity of uses of the term "visualisation". For instance, in a dictionary the following definitions can be found:
- Visualize: form a mental image of .. (The Concise Oxford Dictionary. Ed. Judy Pearsall. Oxford University Press, 2001. Oxford Reference Online.
Oxford University Press.)
- Visualization: The display of data with the aim of maximizing comprehension rather than photographic realism. (A Dictionary of Computing. Oxford University Press, 1996. Oxford Reference Online. Oxford University Press.)
- Visualization: the act or process of interpreting in visual terms or of putting into visible form (Merriam-Webster Online dictionary http://www.webster.com).
These defenitions reveal that visualisation is an activity in which humans are engaged, as an internal construct of the mind (Spence, 2001; Ware, 2000). It is something that cannot be printed on a paper or displayed on a computer screen.
Acconding to Robert Spence, Visualisation is a cognitive activity which a human being engage in. This activity is facilitated by some external representations and results in creating an internal (mental) model in the human's mind.
With these considerations we can summarise that visualisation is a cognitive activity, facilitated by graphical external representations from which people construct internal mental representation of the world (Ruddle et al., 2002; Spence, 2001; Ware, 2000). Computers may facilitate the visualisation process with some visualisation tools. This is especially true in the latest years with the use of more and more powerful computers at low cost. However, the above definition is independent from computers: although computers can facilitate visualisation, it still remains an activity that happens in the mind, even if some authors use the term visualisation to refer to both the printed graphical representation and the cognitive process of understanding an image.