There is evidence of the influence of a great many other philosophers such as Janet, Wallon, Piaget, Wertheimer, Tolman with his neobehaviourism and particularly John Dewey with his work on pragmatism. Others include James with his work on substantialism and Spinoza, a favourite of Vygotsky, with his belief that mental and neuropsychological phenomena were two attributes of the one substance. Although Vygotsky and his followers were accustomed to citing Marx frequently, it is difficult to judge whether his ideas had much influence on the development of the theory, due to the fact that it was generally accepted at the time that Marxist-Leninist philosophy had to be used as the basis for all branches of scientific study irrespective of whether it had any relevance to the topic being studied. The theory has become familiar to western psychologists through the work of Cole and Maltzman, 1969, Wertsch, 1981, 1994, Raeithel, 1990, Kuutti, 1990, 1992, Engestrom, 1990, Kaptellinin, 1992, 1994 and Zinchenko, 1992.

Vygostkian psychology (Vygotsky, 1978, 1981) stated that human mind is constructed through a subject's interactions with the world and is an attribute of the relationship between subject and object. Consciousness is neither reducible to behaviour nor separate from it, but instead is an attribute of the organisation of practical activity. It is the process that organises behaviour. Vygotsky also claimed that consciousness is not an attribute of any particular state or process, but is an attribute of the way in which states and processes such as attention and memory, are organised and functionally related both to behaviour and to each other. It was consciousness that established the connection between the various processes, it both creates them and transforms them. In particular the nature of a goal-directed activity transforms its user. He thus introduced the idea of externally mediated activity, actions that involve the use of external means to reach a goal. This led to the idea that mental processes could only be understood if we understand the tools and signs that mediate them.

A basic tenet of Vygotsky's theory was that tools occupy a mediating role, they mediate human reaction with the world. Tools therefore are social objects with certain modes of operation developed socially in the course of labour and are only possible because they correspond to the objectives of a practical action. Tools can be either external (physical, technical) such as artefacts, instruments and machines or internal (psychological) such as laws, signs, procedures, methods and language. Physical tools are designed to manipulate physical objects (e.g. hammer) while psychological tools are used by humans to influence other people or themselves (e.g. concepts, advertisements, calenders). Since psychological tools are included in the process of behaviour they alter the entire flow and structure of mental functions. Similarly the physical tool (including computers) alters the process of natural adaptation by determining the form of labour operations. A physical tool can be seen as an instrument of labour, a thing which is interposed between a person and the object of their labour and which 'serves as the conductor' of their activity. Although tools expand our possibilities to manipulate and transform different objects they also have a limiting effect in that the object can only be manipulated within the limitation of the tool.

His basic idea was of historically evolving object-oriented practical activity carried out by humans determining the genesis, structure and contents of the human mind. Vygotsky derived his original ideas from an analysis of the features of specifically human activity - work activity, productive activity carried on with tools, activity that is indigenously social i.e. developed under conditions of cooperation and sharing by people. He had isolated the two principal interrelated features basic to psychology. These were the 'instrumented' (tool mediated) structure of human activity and its incorporation into the system of interrelationships with other people. This means that the higher mental functions in humans originate only in the interaction of people with people. Vygotsky did not make a complete analysis of the specific concept of activity, but his theoretical approach pre-supposed the concept as one of its fundamental building blocks. The theoretician who followed up Vygotsky's work and is most closely associated with the development of a coherent activity theory framework was A.N.Leontiev.

Activity, according to Leontiev (1978, 1981) is not a reaction and not a totality of reactions but a system that has structure, its own internal transitions and transformations, its own development. Activity brings together in one unit of analysis both internal, psychological phenomena and an external, objective world. Leontiev was opposed to the separation of what goes on in our mind with what goes on around us and sought to examine the profoundly unique nature of the psychic phenomena that distinguishes it from other 'objective phenomena of reality' (the real world). He sums it up thus: '...our activity seems to occur as it were on two primordially different (and) opposite planes:

• on a subjective ideal plane (i.e. the activity of our consciousness and thought) and
• on an objective plane - the plane of the phenomena of the material world, i.e. our external material activity, the movements of our body, and those internal processes which are their physiological basis.'

The initial and fundamental form of human activity is external, practical activity. The internal plane of activity, inner mental operations and actions, is formed in the process of internalisation. Internalisation is the transition in which external processes with external, material objects are transformed into processes that take place at the mental level, the level of consciousness. During this transition these processes undergo special changes - they become generalised, verbalised, abbreviated; and most importantly, they become the means for further development that transcends what is possible with external activity.

Activity here has its general collective meaning, we need to deal with specific activities, each of which answers a definite need of the subject, is directed toward an object of that need, is extinguished as a result of its satisfaction, and is produced again in other altogether different conditions. Activity types can differ among themselves depending on the difference between their objects. The object of an activity Leontiev says is its true motive, which may be either real or imagined, thus activity does not exist without motive. He called a process an action if it is subordinated to the representation of the result that must be attained, that is if it is subordinated to a conscious purpose. He goes on to say that just as the concept of activity is related to the concept of motive then the concept of purpose is related to the concept of action. Human activity he explains, does not exist except in the form of action or a chain of actions with one and the same action accomplishing various activities and may be transferred from one activity to another. This means that activity is usually accomplished by a certain complex of actions subordinated to particular goals that may be isolated from the general goal. In other words, these actions are seen as goal-directed processes but, in society, these processes are rarely related directly to the goal where even the simplest division of labour leads to 'goal-isolation'. The needs of a person working on an assembly line are not satisfied by the immediate results of producing something, but by a share of the results of the collective activity in the form of salary. The actions that realise activity are aroused by its motive but directed towards a goal. The means of accomplishing actions Leontiev called operations. Just as activity is related to goals, operations he saw as related to conditions. In a case where the goal remains the same but conditions change then it is only the operational content of the action that changes. Actions and operations he saw as the 'units' of activity.

Thus Leontiev introduced a three level structure of activity. Associated with each level is a specific type of unit, the first of which is the unit of activity (detyatel'nost). Here 'activity' means the real activities as opposed to human activity in general and includes such things as labour, formal education and play. It is not determined by the physical context in which humans function but is a socio-cultural creation imposed on the context by the participants. The next level of analysis is the action (deistvie) which, although related to an activity at a particular time can vary independently of it and is transferable to other activities. A particular action could be executed while a person participates in different activities such as work, play or education. The third level of analysis is the operation (operatsiya) and this relates to the concrete conditions under which the action is carried out and includes the resources for reaching the goal. The goal, which is embedded in a specific set of conditions, comprises the task of the activity. This can be summarised schematically:

This structure can however, be divided in a way which depends on the characteristics of each component and on their inter-relationships which in turn are mobile and changeable. In an integrated activity the within-level and between-level organisations are realised by the integration and unification of the functionally defined processes.

The psychological theory expounded by Vygotsky and extended by followers such as Leontiev and others has been discovered by the international community of researchers in human-computer interaction and computer supported cooperative work over the last ten years. For example see Bannon & Bødker, 1991; Bødker, 1991; Draper, 1993; Engestrom. 1990; Gould & Verenikina, 1995; Kaptelinin, 1992; Kuutti, 1992; Nardi, 1992, 1997. Its generally well-developed frameworks may prove more beneficial than traditional cognitive psychology in the analysis of the reaction between humans and machines.

• the goal which is determined by the nature of human actions, their structure and performance,
• the role of mechanisms underlying the integration of a computer tool into the structure of activity,
• the importance of developmental aspects of human computer interaction,
• the significance of social interactions surrounding computer use (Kaptelinin, 1992).

Activity theory provides a paradigm for the description and understanding of the way humans deal with computers within the context of the user's environment. Recently, HCI researchers came to understanding of the importance of the context in which computer-mediated activities take place mainly due to the work of Lucy Suchman (1987). However, contextual factors are rather elusive and difficult to identify (Nardi, 1997, Pennel et al, 1997). It is here that activity theory helps by providing a theoretical framework for describing context of human activity through the structural analysis of the activity, in particular - the highest level of it - motivation. Definition of the motive as the object of transformation within the activity brings together psychological factors (drive, motive, meaning of the activity) and contextual factors (objects as artefacts belonging to a particular social cultural-historical context). In this respect the activity theory approach is not a theory which substitutes for other approaches but it brings a more broader, holistic, integrative philosophical view of the use of information technology by humans.

It also should be noted that activity theory shares a few common ideas with contemporary developed task analysis, which presents a detailed description of individual actions and operations. Activity theory is based on a much broader set of structures dealing with the higher levels of activity and paying attention to integrative relationships between the actions of the activity.

Software developers have been producing systems for many years which purported to be executive information systems. Unfortunately very few of these systems have been successful. The problem cited in the past has always been that the spreadsheet software on which the systems were usually based was not sufficiently sophisticated to deal with the problem. This, however, is no longer the case. Very sophisticated multidimensional databases are now capable of extracting complex combinations of the most obscure of data and presenting it in every imaginable way, all at considerable speed. The problem has changed from one of software engineering to one relating to the psychology of executive users. It has long been known that executives manage in their own particular style. It is also well known that these different styles need different types of information presented in different ways. The question is how do we go about finding out the best mesh of information and business management style so that an EIS is useful to an individual executive.

Existing research which studied personalities and tried to apply it to interface design were unsuccessful because of the difficulty in applying psychological studies of personality to this particular case - they were too far removed from the problem. One possible approach is based on the study of a personal profile of an executive. This profile will consist of an ensemble of the executive's business activities relating to the use of the EIS as a tool embedded in the activities. This will enable the information system to function as a tool for performing the activities and will enable designers to devise ways that an interface can be designed to extract, amalgamate and present information in a way that suits the business management style of the executive. Kaptelinin and Nardi (1997) have recently created an 'Activity Check List' for analysing the structure of activities. It is a good example of the operationalisation of activity theory concepts for practical use.

An example of the influence of identification of different levels of activities is shown in an information retrieval system design (Hyland, 1998). Activity Theory is used to present a more integrated view of the process of information retrieval and suggest how these problems and their solutions fit together. Hyland shows that implicit in much of the information retrieval research is the assumption that the person is engaged in the activity of locating data from a visualisation of some set of the data which is used to navigate and locate that subset which is required. However, using the specific meaning of 'activity' as applied in activity theory this assumption is incorrect. In such cases, the search for data would be an action that is carried out to complete the activity of writing a report or other broader based undertaking. Hyland goes on to say:

It is important to distinguish between the various levels of interaction. Bannon (1991) has highlighted the case of discretionary users who might use computers to assist with everyday tasks but who have alternative means of accomplishing them. If an information retrieval systems is built on the assumption that all users work at an operational level then discretionary users, for whom the use of the system is in itself a significant activity, will reject the system