The theme of this special issue is ''The Role of Cognitive Science in Human -Computer Interaction'' (HCI) . A generally accepted definition states that the main goal of HCI is to advance the design , implementation , and use of interactive computing systems by human beings (ACM , SIGCHI , 1992) . Since the current primary use of computers is as tools for acting on and for observing the (information) world , the role of cognitive science-interpreted broadly as an endeavour to understand intelligent behaviour-is , consequently , tied to the questions :
$ how do our interactions with computing systems af fect our representations of the objects that we manipulate? $ how does interactions design influence our senses and our actions? $ how does using computers to perform tasks transforms our notions of the relationships that exist in the world around us?
For HCI , the rationale for entering into a research partnership with cognitive science is to apply knowledge of cognitive functioning to maximize desirable outcomes of interactions and to minimize any undesirable ''side-ef fects'' . From the above viewpoint , the quality of cognitive science contribution rests on the flexibility with which descriptions of cognitive functioning permit engineering refinement .
The relationship between science and engineering , of course , is not necessarily direct or simple (Carroll & Campbell , 1989) . An example that helps to demonstrate this may be provided by design problems associated with virtual reality (VR) systems . One common concern is how to overcome dif ficulties experienced by human visual system when interacting with computer-generated three-dimensional dynamic spaces presented on two-dimensional displays . Science can supply understanding of how human depth and motion perception operates in natural and in virtual environments (VE) , and so , for instance , help to supply information about โ Author for correspondence . 731