In other words, it is recognised that a specific skill is needed to write a book, design a lab or write a computer programme, and that using these skills in some way modifies the course of nature. The same level of artificiality is not recognised when the behaviour of teachers and students comes to be defined. It is highly likely that this behaviour is seen as a natural talent for teaching in the former, and a natural inclination to learn in the latter.(2) As is always the case when discussing 'natural' characteristics, it is taken for granted that these exist in different proportions, so that there are good teachers and less good ones, and students who learn their lesson with greater or lesser ease.(3)

What makes the naturalistic approach insidious is that it is founded on an implicit analogy between, on the one hand, the practices of primary adaptation to life, in which adult individuals naturally tend to facilitate the acquisition of skills in the new members of the species, and, on the other, teaching. And yet teaching involves the practices of secondary adaptation, and it aims to satisfy symbolic needs which have cultural roots and are extremely variable in time and space. Secondary adaptation can only be artificial. It is constructed in order to achieve specific aims by altering the 'spontaneous' sequence of phenomena in the process of the subjects' development. It is only because these intentions are generally shared and deeply internalised in the attitudes of adults that they are considered "natural", and that the analogy between primary and secondary adaptation is strengthened.

To consider teaching an artificium is to define it as a set of solutions by means of which secondary adaptation takes place. It is nonetheless clear that this definition cannot be applied to the "weak" interpretation, i.e. that only the artifiality of teaching tools is recognised. It can only be applied to the "strong" interpretation that also recognises behaviour as an artificial component of teaching. Fundamentally different ways of teaching are accredited according to whether the weak or the strong interpretation prevails.(4)

If the weak interpretation is accepted, greater emphasis is placed on the personal characteristics of the subjects involved in the teaching activity, and these personal traits take on a causal value. Since the distribution of personal characteristics over the population is highly dispersed (without external mechanisms that modify the dispersion, such as social filters in the access of students to schools which inevitably leads to limiting the numbers of teachers) the results of the teaching activity are equally dispersed.

If, on the other hand, the strong interpretation is admitted, the number of variables to which to link the results increases, as do the chances to direct the teaching process towards achieving specific aims. It is difficult (and, in some cases, impossible) to modify the personal characteristics of the subjects involved in the teaching activity, but if it is accepted that the behaviour of the teacher can be modified, there is much greater room for manoeuvre. Modifications could even mean attributing a teaching function to a collective subject rather than considering it a personal prerogative.(5)

Technological messianism has been perhaps the main ideological component of the debate on teaching in these last decades of the twenetieth century. The urge to modernise schools by buying up technological equipment that has never been tested for didactic value is the consequence of ideology prevailing over scientific demonstration. In the case of distance learning, the paradox is even more striking. The messianic elements of the debate carry disproportionate weight, while serious reflection on the solutions that are actually put into practice is left aside.(8)

As a result, attention is detracted from the real problems that present themselves in the specific conditions of distance learning, and is focused, rather, on marginal issues that are rarely able to create a structural impact.

This explains the paucity of theory, for which ideology is a poor surrogate.(9) Apart from any other considerations, to stress technical solutions widens the gap between classroom and distance teaching. Likewise, significant theoretical contributions can only be derived from the identification of structural components. Taking as given the umbrella definition of teaching as a set of forms of secondary adaptation, it is important to identify the structural element that allows secondary adaptation to be distinguished from primary. It is not difficult to find learning conditions in primary adaptation - such as conditioning or imitation - that also exist in secondary adaptation. These learning conditions do not require any particular organisation because any less-expert subject acquires skills in a context where at least one person is more expert, whether that person was intending to teach or not.(10)

The paucity of the theory behind distance learning also depends to a great extent on the difficulty of liberating structures of phenomenal associations. Just as it did not seem a good idea to create an association between the well-established concept of school and the structure supplying distance learning, it was also decided not to develop research on distance learning along the same lines as research on classroom learning. In the first prolonged stage, that started with pioneers in the nineteenth century and continued until the 1970s, distance teaching consisted basically in organising people's study along similar lines to scholastic curricula and sending off regular batches of learning materials. The imitation of a classroom situation was completed by proposing exercises to make sure the work had been digested. However impoverished, it must be stressed that this early stage was not so different from teaching practices commonly found today in schools and universities. The gap between the two contexts has widened in recent decades due to the increase in technological solutions for communication and data processing. These have fed optimistic predictions that difficulties in establishing a teaching relationship at a distance can be overcome.(12)

The mistake was to place too much emphasis on overcoming distance and too little on the teaching objective. This led distance learning pioneers to seek conceptual proximity to other sectors equally involved in the transfer of messages across wide geographical spaces rather than to other teaching activities. The closest frame of reference seemed to be the theoretical and technical approaches developing more or less in parallel by the ever-advancing mass media.

The fact that the mass media responded to completely different objectives to distance learning was never taken into account. The mass media, in fact, tends to broadcast as many messages as possible to as wide an audience as possible. It does not aim to organise these messages in order to bring about learning, that is, a modification in an individual's skills over a given time span. Its objective is simply to make the messages as accessible as possible to as great a number of potential users as possible. What counts is not whether these users actually acquire the messages, but that they have had the chance to do so, and that there is some comprehension, however superficial, on their part. In this way, the characteristics of the users determine those of the messages: as a consequence, widening the audience can only be achieved by lowering the level of cultural references needed to understand the messages. The organisation of the messages tends to satisfy the needs of the lower levels of potential users.(13) More complex subjects are thus simply not broached. Instead, metaphors of daily life are adopted, a more limited vocabulary is used, syntax becomes prevalently paratactical and there is a drastic reduction in synonyms, with the result that semantic nuance is lost. The only didactic criteria that can be recognised in these forms of communication is that of popularization, with the resultant loss of specificity in the messages to be communicated. All this has very little, or nothing, to do with good teaching, either in the classroom or at a distance.

At this point it is important to identify what conditions allow the artifice of teaching to take place, artifice meaning, as explained above, the mediation that makes explicit the implicit components that would otherwise get in the way of understanding.

The various interpretations that have been given through time reflect the most important teaching models. To simplify matters we can divide these models into two categories. The first tends to make the virtual receiver overlap with the real receiver of the learning proposal, while the second considers the virtual receiver a model on which to base its interpretation of the characteristics of the real receiver. In the former case the message is established regardless of the characteristics of the receiver; in the second case, the message is gradually adapted on the basis of a virtual prototype. The information regarding the receivers' characteristics can thus be used in two different ways:

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It is possible to integrate the data regarding a given number of receivers and thus obtain a model in which the variables of single traits occupy a central position in the distribution. This integration is possible both on a diachronic and a synchronic plane. Teachers who justify their choices on the basis of previous experience draw on average characteristics of generations of past students, often implicitly (diachronic integration). If the data is collected at the beginning of a course, and if the learning message is defined on the basis of that data, the reference values are central compared to the specific intervention situation (synchronic integration).

Even when data regarding the characteristics of the receivers is used in order to adapt a learning message to individual needs, and when a gradual closing of the gap between real and virtual receivers of the teaching message is obtained, it is possible to proceed with diachronic and synchronic integration. The integration is diachronic if the message is adapted on the basis of observations of the behaviour of a receiver over a long time-span and in relation to similar learning tasks. Integration is synchronic if the profile of the receiver is continuously reconstructed and if, in parallel, the learning message is adapted.

1. The diachronic integration of receivers' characteristics and the uniform formulation of the message. This is the most traditional teaching typology, in which the cognitive underlayer is generically justified by experience. In practice, the virtual receiver of the teaching intervention is delineated through the integration of the characteristics of real receivers who have received similar learning proposals in the past. The differences between students from past generations are compensated for by referring to average values in the distribution curve. In the classroom, this teaching typology is subject to the personality of the teacher and to his or her experience. In distance learning the virtual receiver is defined on the basis of very similar procedures. These can be justified by the analogies that can be found with classroom teaching and by the results achieved on previous occasions. This approach may be traditional, but it is behind many high-tech teaching proposals such as television messages, multimedia programmes and text-books over the internet.
2. The diachronic integration of the receivers' characteristics and an individualized message formulation. The receivers' characteristics are gleaned through prolonged observation in learning situations. If these situations are dual (one teacher taking care of one student), the message takes account of the talents, interests and skills the student has already acquired. If the observation involves a group of students (as in many teaching practice situations), the subjects are aggregated on the basis of a criterion, usually a forecast of their success. The message is then modified according to the characteristics considered when setting up the groups of students. Something similar takes place when compensatory activities are organised: the message is modified taking into account previously encountered difficulties. Adaptation by means of this typology is very slow, and since for the most part it takes place by admitting failures it can take on negative connotations for the students.
3. Synchronic integration of the receivers' characteristics and a uniform formulation of the message. This typology is behind teaching approaches based on some form of preventive equalization of the students' characterstics (an admission test, for example, or crash courses to fulfil requisites). It is presumed that students who have been thus levelled out are in a position to receive a uniform message. In other words, the general level is the touchstone in defining the virtual receiver of the learning message. The weakness of this approach is that the initial levelling takes place in relation to a limited number of variables. It is therefore highly likely that during the learning process the differences between students will re-emerge. This typology also includes approaches that envisage differentiated levels, based on talent or competence for example, with different expectations for each. These approaches centre on deterministic interpretations of teaching, and therefore basically renounce the idea of quality in teaching.
4. Synchronic integration of the receivers' characteristics and an individualized formulation of the message. The learning message is continuously adapted to the needs of the receiver. Because these needs are almost entirely defined by the initial cognitive and affective characteristics of the students, if these characteristics reveal that there are difficulties the quality of the teaching must be improved. Otherwise the distribution of dependent variables simply reproduces the initial characteristics. The fourth typology envisages, then, an personalised teaching proposal. The typology requires complex know-how and techniques, to the extent that it could be called a "technological" approach, independently of the tools used in the teaching activity. If technology is considered a complex form of knowledge aimed at know-how (and not merely at the ability to produce or utilise complicated instruments), there is, in fact, a similar complexity in personalised teaching approaches compared to those based on a uniform learning message. Personalisation requires continuous analytical information on the progress of the learning process and relies on the ability to modify the message according to the difficulties with which each student is effectively meeting. It is essential, therefore, to make continual decisions and to direct the process towards achieving the aims of the teaching intervention.

The technology of teaching, then, requires a strategy crowded with decisions, according to which the choice of behavior pattern is based on an analytical knowledge of the conditions in which one has to teach, and which has the aim of improving the quality of teaching to respond to individual learning needs.

The density of decisions that characterises the fourth typology (synchronic integration of the receivers' characteristics and an individualized formulation of the message) is conditioned by the existence of a continuous flow of information. This flow must be explicitly stimulated, because it is essential that the information precisely reflects students' attitudes to single aspects of the teaching proposals.

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In both cases, interaction is the result of artificium, that is consciously organised activities with precise objectives.

The frequency with which decisions must be made, which is strictly linked to the frequency of interaction, is an essential element of individualized teaching procedures, both in the classroom and in distance learning. The difference between the two ways of teaching has nothing to do with the presence or absence of interaction, but with the fact that in the classroom interaction is direct whereas in distance teaching it is mediated. It could be added that in the classroom there are not only the interactions explicitly envisaged but also those whose affective and relational roots can be found in the verbal and non-verbal messages exchanged in the teaching context. In distance learning, which distinctly lacks the physical continuity between the formulator and the receiver of the message, interaction is predominantly cognitive, and responds to the activation of stimuli and to specific objectives.

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Precisely because of the lack of informal interaction, the frequency and quality of interaction could be considered a criterion in judging the effectiveness of distance teaching. With this aim in mind, it is possible to divide up the different proposals according to whether they provide a low, medium or high frequency of interaction. (see Fig.9):

• Low frequency interaction: interaction is limited to formal moments of evaluation, either at the end of the course, or at the end of segments of the course(teaching units or groups of units). Interaction takes place only at the end of a course of learning, and therefore cannot reflect back on the teaching activity. at least not immediately. For students, interaction of this kind provides a global confirmation of whether his or her performance conformed to the objectives of the course. Study conditions for students involved in distance learning with low frequency interaction are very similar to those for self-taught students. The only differences are that the contents of the course follow a precise programme designed to help acquire specific skills and that there is a test at the end of the course to see whether these skills have been acquired. It is important to establish that without these minimum requirements, it is wrong to consider the situation one of distance teaching. If the definition is over generalised, every form of study in which teachers and students are not required to be in the same place at the same time could be referred to erroneously as distance learning.
• Medium frequency interaction. These proposals are characterised by the careful detail with which the teaching project is drafted. There is a precise description of the entry level of the students and an analytical indication of the aims to be achieved at the various stages of the distance learning course, Interaction takes place through check-up tests with results indicating the quality of the work given in. Students therefore receive either confirmation that the work is correct or a recommendation to undertake further study if the results do not conform to the objectives. These proposals deserve to be described as "distance learning". There is a certain symmetry with good quality traditional teaching in which the burden of adaptation is an essential component of the students' commitment. The opportunity for frequent analytical feedback means that the teaching message can be rectified, though this may only happen in part and anyway the adaptation is generalised not specific.
• High frequency interaction. There is a decided increase in frequency of interactions in a classroom or distance learning context when feedback is used to adapt the message to the specific needs of individual students rather than to verify its general effectiveness. When there is high frequency of interaction in a teaching situation, the roles of the teacher and student are less clearly separated because the burden of adaptation is shifted from the students to the teacher, or, in the case of distance learning, to the structure supplying the teaching.

Frequency of interaction

The optimum frequency cannot be established in abstract. It should depend on the actual learning path of each individual student. If the teaching proposal takes account of individual needs, the transition from an entry level ( t0) to an exit level (tn) will pass through various intermediate stages (t1, t2, ...). Each of the intermediate stages is identified by a specific learning objective (o1, o2, ...). As a consequence, the learning path of each student can be divided up into steps (s), over a period of time (t) and with an objective (o). Since the path is individual, however, the transition from s0 , the first step at an entry level, to sn, the last step at an exit level, does not necessarily follow a numerical order. The path follows an individualized order according to each students' needs. It is therefore necessary to have an element of evaluation (e) so that each step can be taken at the right time. The evaluation element is thus decisive (see Fig.11).

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Since the number of steps is variable, there is also a change in the number of actual interactions, meaning adjustments made during the learning path as the result of an exchange between the teacher and the learner regarding evaluation. When defining a model, one must estimate the number of potential interactions (ip) and calculate the number of real interactions that take place (ir). The number of potential interactions grows in relation to the number of steps and the number of alternative messages that one is able to produce for each step (am). Thus ip = np am

While the number of potential interactions increases rapidly, the number of real interactions will tend to overlap with the number of steps, unless a differentiation in evaluation takes place within the alternative messages.

The teaching message can be considered optimum for a given student when he or she has acquired all the skills envisaged by the teaching programme.

Text Notes:

1. Didactica magna (the work in which the definition of teching appeared) was published in 1657, with a sub-title that annotates Universale omnes omnia docendi artificium exhibens. In the dedication to his readers Comenius added Didactica docendi artificium sonat.
2. On the different ways of viewing teaching, see B. Vertecchi Interpretazioni della didattica, Florence, La Nuova Italia, 1990.
3. The naturalistic idea is lent greater weight by statistical analysis of the distribution of descriptive variables in the population. It has been said, for example, that the distribution of the main attitudinal variables is on a bell curve and corresponds to the casual distribution of a binomial variable. Analyses of the distribution of variables in school learning, which seemed (and still seem in "traditional" school environments) to be strongly correlated to the variables of attitude and talent, have reinforced those deterministic interpretations of students' potential for success. These arguments have been severely criticised by B.S. Bloom and others, in the context of a specification of a theoretical framework for the proposal to individualise teaching known as 'mastery learning'. See J.H.Block (Ed.), Mastery learning, Procedimenti scientifici di educazione individualizzata, Torino, Loescher. The question is still pressing and contrinues to stimulate lively debate. A recent debate followed the publication of an essay by R. Herrnstein and C. Murray called The Bell Curve: Intelligence and Class Structure in American Life, New York, The Free Press, 1994. Herrnstein and Murray's message is not new. Their conclusions were also reached by A.R. Jensen in a 1969 article in which he claimed that all efforts made by US education boards to compensate for socio-economic disadvantage, and especially ethnic differences, were basically useless (see How Much Can We Boost IQ and Scolastic Achievement? Harvard Educational Review, Winter 1969). Reactions to this essay highlight the ideological overtones of any references to the curve of normalcy and cover up for conservative views on social issues. See R.Jacoby, N.Glauberman (Eds.), The Bell Curve Debate, New York, Random House, 1995; J.L.Kincheloe, S.R.Steinberg, A.D.Gresson III (Eds.), Measured Lies The Bell Curve Examined, New York, St. Martin's Press, 1996.
4. In a "strong" interpretation, teaching embraces a plurality of dimensions, ranging from cognitive, affective and relational. In a "weak" interpretation, one or more dimensions are stressed over the others. This takes place in many of the didactic proposals that present themselves as "alternative" but in which emphasis on one component of teaching takes away from all the others. For a review of "strong" and "weak" interpretations, see B.Vertecchi "La Didattica", in B. Vertecchi, La scuola italiana verso il 2000, Florence, La Nuova Italia, 1984, pp.370-381.
5. This is the case in distance learning and in many models of teaching organisation that have developed in recent decades which base themselves, in greater or lesser measure, on specialisation and the sharing out of teaching tasks.
6. A recurring ideological component of recent debates on the usefulness of technology in teaching is that of consumerism. See B. Vertecchi "Per una critica del consumerismo educativo," Cadmo, 1,2, 1993, pp.5-16.
7. "Renewal" in education sums up an attitude sustained by the Manichean contrast between knowledge and available resources (considered evil) on the one hand, and the knowledge and resources able to replace them (considered good) on the otehr. Since the substitution cannot be verified, any credit given to it can only be ideology. This ideology is highly destructive as it is the antithesis of scientific rationality, which procedes along the lines of experimental verification of innovative hypotheses.
8. This disproportion is even more striking if one considers the historical development of distance learning, in which the emergence of a new demand for education was the dynamic component. The availability of technological resources has improved some aspects of the education supply, but it cannot be considered an essential component in drawing up which solutions to adopt. Still today, the vast majority of distance learning uses traditional teaching tools and it is difficult to say to what extent solutions relying on complex technology have contributed. This is partly due to the extremely short market life of any of the technological proposals. It is not such a rare occurrence when an innovative prototype is presented with great verve but never followed up because the planning and realisation of the educational programmes linked with it have become obsolete. In many cases it is also important to ask oneself why substitute programmes that work with others that have a similar utility but that require many more resources both for the insitutions that supply education and for those who benefit from it. The impression is that all too often the creation of new markets becomes more important than logical didactic development. For a general introduction to the problem of distance learning, also considered in its historical dimension, see D.Keegan, Principi di istruzione a distanza, Firenze, La Nuova Italia, 1994. An interpretion of the history of distance learning can be found in L.Sauvé, "Origini e sviluppo dell'istruzione a distanza," Istruzione a distanza, IV,5, 1992, pp.37-46.
9. By poverty, we mean there is very little theoretical thought on the didactic aspects of distance learning, though there is a great deal on other aspects. These contributions have helped identify specific structural components and decidedly widened the conceptual repertoire for interpreting distance learning. From this point of view, an essential contribution has been made by O.Peters, who identified the peculiarity of the productive mode in distance learning. See O.Peters in "Distance Teaching and Industrial Production: a Comparative Interpretation," in D.Stewart, D.Keegan, B.Holmberg (Eds.), Distance Education. International Perspective, London, Croom Helm, 1983, and "The Iceberg Has Not Melted: Further Considerations on the Concept of Industrialisation and Distance Teaching," Open learning, IV, 3, 1989.
10. The age old question of the relationship between upbringing and education comes to light once again. Certainly upbringing includes both primary and secondary adaptation, while education focuses mainly on secondary adaptation. This is not to say that primary adaptation does not also mean acquiring skills; simply that these skills are, as it were, implicit in the culture of the social context. From this viewpoint, an essential contribution has been made by the reconstruction of educational models pput forward in anthropological research (see M.Mead, R:Benedict, C.Levi-Strauss). See also M.Callari Galli, Antropologia culturale e processi educativi, Florence, La Nuova Italia, 1993.
11. It is surprising how research on distance learning and on classroom teaching appears to belong to two completely different worlds. Glancing through bibliographical references, one can see that it is a rare event when research on school teaching mentions research on distance learning and vice versa. This fact is even more difficult to explain when transversal aspects of the two ways of teaching, such as those regarding the definition of teaching strategies, testing tools, the use of technology for teaching and learning, are considered. Collaboration between the two fields could be fruitful when discussing these aspects in particular. As far as teaching strategies and innovative tools (for testing and communicating the learning message) are concerned, distance learning presents a particularly good experimental environment because there are fewer personal variables involved in the teaching relationship. This has been demonstrated in the Laboratory of Experimental Pedagogy at the Department of the Science of Education of Rome III University. The need to find out more about some of the characteristics of distance students (mostly a matter of foreseeing which objectives would create most difficulty) has led to the formulation of a new evaluative theory (analogical evaluation) and to a new set of tools (analogical tests). This new theory and set of tools have been used to define a new model of personalised (known as DIVA, or Personalised Didactics through Analogical Evaluation) which has been experimented in various secondary schools in Italy over the last few years. See B.Vertecchi, E.Nardi, M.La Torre, Valutazione analogica e istruzione individualizzata, Firenze, La Nuova Italia, 1994; E.Nardi (Ed.), Per una didattica individualizzata. Gli sperimenti Diva, Naples, Tecnodid, 1997.
12. One of the reasons for the lack of attention regarding distance learning could be the conviction, still commonly held, that distance learning is a second-best solution to be adopted only if normal, that is classroom, teaching cannot be provided. Due to this general opinion, many people resort to distance learning not because they are convinced it is a good idea but because they have no choice or as a result of socio-economic conditioning. This conditioning did not regard the better-off students but those who were less well-off, and within the same social class some categories were more affected than others (e.g. more women than men, more agricultural workers than blue-collar workers, etc.). The resistance of negative connotations reflect negatively on the possibilities for increasing the supply of distance learning in order to satisfy the growing demand for adult education. It is precisely in these situations that distance learning is not a second best.
13. It is important to take notice of the divergent lines along which the mass media and teaching have developed. While the mass media is dominated by the need to reach and ever-wider audience, teaching has evolved around a growing attention on individual needs. In the former, the attempt is to find a logic for collective thought, gathering together shared factors and leaving aside those who express divergent views; in the latter, divergent factors become the main focus of the activity.