The Use of Diffusion Theory in Marketing: a Qualitative Approach to Innovative Consumer Behavior

ABSTRACT - This paper offers preliminary findings from a qualitative study of owners of compact disc players. The focus of the research was to explore consumers' reasons for purchasing particular products, their reasons for postponing purchase decisions, and their reasons for resisting other product purchases. The underlying framework for this research is that of diffusion of innovation, particularly as it is used by consumer behavior researchers. This paper argues for a new approach to the study of consumer innovativeness.

Citation:

Tina M. Lowrey (1991) ,"The Use of Diffusion Theory in Marketing: a Qualitative Approach to Innovative Consumer Behavior", in NA - Advances in Consumer Research Volume 18, eds. Rebecca H. Holman and Michael R. Solomon, Provo, UT : Association for Consumer Research, Pages: 644-650.

Advances in Consumer Research Volume 18, 1991      Pages 644-650

THE USE OF DIFFUSION THEORY IN MARKETING: A QUALITATIVE APPROACH TO INNOVATIVE CONSUMER BEHAVIOR

Tina M. Lowrey, University of Illinois

ABSTRACT -

This paper offers preliminary findings from a qualitative study of owners of compact disc players. The focus of the research was to explore consumers' reasons for purchasing particular products, their reasons for postponing purchase decisions, and their reasons for resisting other product purchases. The underlying framework for this research is that of diffusion of innovation, particularly as it is used by consumer behavior researchers. This paper argues for a new approach to the study of consumer innovativeness.

INTRODUCTION

The theory of diffusion of innovation has -developed across many fields of research over the past several decades (Rogers 1983). While the study of diffusion originated in sociology and anthropology, marketing and consumer behavior theorists have adopted the general paradigm for use in their fields to explain new product acceptance and diffusion over time. Intuitively, it is obvious that there are inherent differences between sociological or cultural innovations and the introduction of new consumer products. However, for the most part, the marketing tradition of diffusion research has accepted the general theory without questioning many of its underlying assumptions (Gatignon and Robertson 1985). Very few studies exist in the consumer diffusion literature which challenge the basic conceptual framework. Criticisms of diffusion research are outlined clearly by Rogers (1983), particularly the pro-innovation bias of most diffusion researchers.

The pro-innovation bias is defined by Rogers as "... the implication of most diffusion research that an innovation should be diffused and adopted by all members of a social system, that it should be diffused more rapidly, and that the innovation should be neither re-invented nor rejected (p. 92)." Causes of this bias include the funding of the research by the change agencies themselves and a focus on studying only successful innovations (after completion of the diffusion process). Although the concept of the pro-innovation bias is much more complex than this brief discussion implies, it is clear that this bias affects two diffusion research areas in particular. The first is the categorization of individuals into adopter categories based on innovativeness and the subsequent attempt to assign personality characteristics to members of each adopter category. The second is the study of characteristics of innovations themselves.

ADOPTER CATEGORIES

Rogers (1983) identified five adopter categories of innovativeness. These categories fall along the normal frequency distribution curve. In simple terms, the first 2.5% of a given social system to adopt a particular innovation are labeled as innovators. The next 13.5% who adopt are considered early adopters. The third category, the early majority, constitute 34% of the population under study, followed by a group of the same size (34%) known as the late majority. The final category is made up of the last 16% to adopt (and also, presumably, non-adopters). The individuals in this category are known as laggards.

Rogers describes dominant characteristics of each of these categories briefly, as follows: innovators are venturesome, early adopters are respectable, the early majority are deliberate, the late majority are skeptical, and laggards are traditional. In addition; socioeconomic characteristics, personality-variables, and communication behaviors are analyzed across adopter categories in an attempt to further define the individuals from each category. The use of this categorization scheme presents two specific problems for marketing researchers. One critical observation which can be made is the general lack of necessity implicit in the majority of consumer offerings. Given this fact, the classification of nonadopters (or slow adopters) into the laggard category (with the negative attitude implied by the label) leads to an incorrect placement of blame. Assumptions are made regarding the personality characteristics of a non-adopter, such as lack of rationality and/or aversion to risk. What is not discussed IS the fact that many consumer products simply do not fit all individuals' needs. Rogers (1983) explains this quite succinctly, "...we have often assumed that all adopters perceive an innovation in a positive light, as we ourselves may perceive it. Now we need to question this assumption of the innovation's advantage for adopters (p. 100)."

A second question for consumer behavior researchers to ask is how valid a categorization scheme based on innovativeness can be when individuals are not consistently innovative. Again, this problem emerges due to the vast amount of products available which are not necessities. To claim that innovators are venturesome while laggards are traditional overlooks the fact that the same individual can be placed in either category depending on the product under study. Robertson (1971) follows this line of thought by asking whether or not a general innovator may exist, concluding, "...consistency of innovativeness cannot be expected across product categories, but can be expected within product categories and, sometimes, between related product categories (p. 111)."

Although recently Feick and Price (1987) have defined "market mavens" as individuals who possess information about many types of products and the marketplace in general, their focus is on common household products. When shifting attention toward innovative consumer technologies, such as compact disc players, VCR's, and personal computers, it becomes more difficult to find such generally information-rich individuals. Although there are some "technologically advanced" consumers who embrace each new innovation that comes along, there is an innate amount of specialization in this more complex area of technological products. Thus, you are more likely to find audiophiles, PC buffs, etc. who have a great amount of information about one specific product category. This fits well with Robertson's theory of innovation within a product category. However, a problem emerges with Robertson's theory when focusing on consumer technology innovations. When one uses product category as a unit for differentiation among innovators, the definition of a product category becomes critical. For example, if the product category is too broad, i.e., sound reproduction equipment, than individuals will not be likely to adopt within the category. This is due to the duplicate technologies which are offered to consumers. An innovator within such a category may adopt one particular technology and reject all others.

INNOVATION CHARACTERISTICS

This leads to the second major area of diffusion research which is impacted by the proinnovation bias, the objective characteristics of the innovation itself. Rogers (1983) outlines five factors: relative advantage, compatibility, complexity, trialability, and observability. Quite briefly, relative advantage refers to the innovation's superiority to existing products or methods. Compatibility is the degree to which an innovation fits with existing values, needs, and ideas. Complexity refers to the fact that an innovation may be difficult to understand or use. Trialability is the ability to experiment with the innovation before total commitment is made (a form of risk-reduction). Observability refers to the visibility to others of the results of adopting a given innovation. These characteristics tend to become oversimplifications when applied to specific innovations, particularly in consumer behavior and marketing. Several researchers have identified additional ways to characterize innovations. For example, Fliegel and Kivlin (1966) argued for innovation-specific attribute characterization due to the difficulty in accurately defining and comparing attributes across disciplines. Their agricultural emphasis utilized 15 variables, some of which are identical to Rogers' classification scheme. For instance, divisibility for trial is comparable to trialability, and complexity appears in both. However, Fliegel and Kivlin include such factors as initial cost, continuing cost, and pervasiveness (which pertains to the innovation's contribution to additional changes).

Perhaps one of the most valuable additions to diffusion theory in this area for marketing purposes has been Robertson's (1971) simple innovation continuum. Innovations may be either continuous (resulting in little or no behavioral change), discontinuous (requiring major change), or may fall anywhere between these two endpoints. This basic theory has been extended by Heany (1983), whose continuum begins with style changes, progresses through product improvements, and ends with new products for new (undefined/undimensioned) markets. What each of these approaches suggest is that, in the area of consumer products, a minor innovation will have associated with it a different set of salient attributes than those associated with a major innovation. The difficulties which arise in trying to apply traditional innovation attributes to consumer products in general become increasingly problematic when focusing on new consumer technologies.

These technologies have additional factors which simply are not adequately addressed by existing diffusion theory. Several consumer researchers have begun to tackle the issues which are encountered when studying such discontinuous technologies. One interesting area which has been addressed by behavioral researchers is the impact of consumers' perceptions of innovation attributes and the subsequent effect on consumer expectations. While traditional diffusion research focuses on objective descriptions of innovations, this line of inquiry isolates the consumers' subjective perceptions as one of the most important determinants of successful diffusion.

Fliegel and Kivlin's (1966) study was one of the first to attempt to measure the individual perceptions of (in their case) farmers rather than relying on an objective listing of attributes by the researchers themselves. The study successfully obtained individual perceptions using attribute scales, which were then pooled over the sample to estimate shared community perceptions. They found that, as expected, those innovations perceived as least risky and most rewarding had the highest chance of successful adoption.

In the two decades since this study very few perceptual research designs have been incorporated into marketing diffusion research. The few that have all contributed greatly to our understanding of the very complex interaction between consumer perceptions and successful innovations. Ostlund (1974) found that perceptual variables were much more successful at predicting purchase outcome for low-risk innovations than were respondent characteristics. In a more recent study, Wilton and Pessemier (1981) investigated the importance of consumer perceptions in acceptance of a major, discontinuous innovation, finding that changes in perception which occur as product information is received are directly related to successful diffusion of innovations. In another study of a highly discontinuous technology, Dickerson and Gentry (1983) compared demographic, psychographic, and technical product experience variables of adopters and non-adopters. They argue that the differences between their profile and Rogers' original adopter categorization stem from the nature of the innovation, "We suggest that the nature of the adopter of an innovation is partially a function of the characteristics of the innovation itself (p. 233)." This points directly to the complex interaction of adopter categories and innovation characteristics to which this paper previously alluded.

A key characteristic which the majority of innovative consumer technologies share is the increasingly rapid rate of introduction of improvements and/or replacements. This factor differentiates this particular area of diffusion research from many others. Norton and Bass (1987) incorporated this factor into a diffusion model. In particular, they argue that substitution effects will impact the diffusion of an earlier technology. For example, customers who have not yet adopted a given innovation will instead adopt the newer, displacement technology. Additionally, adopters of the prior technology may "reject" and shift to the newer innovation. This will not completely halt the diffusion of the earlier innovation but will, of course, significantly affect it. Holak, Lehmann, and Sultan (1987) also address this issue, focusing on its relation to consumer perceptions and expectations. They hypothesized that consumers incorporate -expectations of technological improvements and price reductions into their purchase decisions which results in purposeful delay of purchase. The results of their study showed a positive relationship between technological improvement expectations and delayed intention to purchase. Price reduction expectations were not shown to be related to intention.

One area of study which has been overlooked is how individuals themselves would describe the decision-making process they may utilize when adopting innovative consumer technologies. The focus of the research reported in this paper was to explore consumers' purchase behaviors by allowing each informant to explain in detail the decision-making process which was followed prior to adoption of a range of innovative consumer technologies, as well as their reasons for postponing or even resisting other product purchases. What are the actual decision-making stages experienced by consumers, in their own words? Are these decisions purposive and rational, particularly decisions to delay purchase? Can consumers be easily placed into a specific adopter category and thus be presumed to exhibit particular personality characteristics (which will predict attitudes toward other innovations)? What are the attributes of innovative consumer technologies which appear to be most salient in this process? To increase understanding of this complex phenomenon, a qualitative approach was taken to ensure that the everyday life experiences, attitudes, and perceptions of these individuals would be captured while attempting to minimize researcher as

METHOD

Data were collected through depth interviews of nine informants, all of whom had purchased their own compact disc player. The findings being reported here are based on 17 hours of interviews with individuals who responded voluntarily to a study request placed in record stores throughout the community. Although no attempt was made to select informants based on any demographic criteria, the volunteers were all males, ranging in age from late teens to early forties, and included college students (both undergraduate and graduate), local businessmen, and self-employed individuals. In addition, informants differed in how long they had owned compact disc players, ranging from several years to only a few months.

At the request of each informant the interviews were conducted in the researcher's office. Two separate hour-long sessions were held per informant, with the exception of one individual who preferred to complete both interviews in a single session. Although ownership of a compact disc player was a prerequisite for participation in the study, the interviews included detailed discussion of an entire range of innovative consumer technologies. This enabled the researcher to examine commonalities and/or contrasts in decision making behavior across products and product categories. The specific products discussed are listed below:

CD players, portable disc players, portable cassette players/recorders, stereos/stereo components, digital audio tape players, and electronic musical instruments

personal computers, modems, and printers

televisions, VCR's, laser disc players, video games, and HDTV

answering machines, cordless phones, and car phones

disc cameras and camcorders

The purpose for including such a varied array of products was to see if individuals followed different processes for products from different categories, and also to enable informants to focus on products which were of particular importance to them personally.

In the first session, each informant discussed in detail the process they went through before purchasing their compact disc player and another appropriate product of their choice. Discussion was guided by a structured but open-ended interview schedule. However, the informants themselves were more responsible than the interviewer for the products discussed, the major focus, and direction of the interviews. The second session focused entirely on products which the informants did not own. These were divided into those which were not desired at all versus those which were desired in varying degrees. Again, the informants were responsible for categorization of these products rather than the interviewer. Depth probing was utilized to examine the reasons for an individual's lack of desire for a product and/or delay of purchase.

Although this study is quite limited in its scope and is not an example of naturalistic inquiry, data analysis was guided by techniques outlined by Glaser and Strauss (1967), Miles and Huberman (1984), and Lincoln and Guba (1985), including the constant comparative method for establishing categories and the search for emergent overall themes. What is reported here are the preliminary findings of the analysis of over 300 pages of transcripts from 16 60-minute microcassette audiotaped interviews and one 60-minute videotaped interview.

THEMATIC FINDINGS

Three overall guiding categories which shaped the analysis of this data were the purchasing process these individuals described for the two owned products discussed, the reasons for delaying purchase of desired items, and the attitudes and perceptions of items which were not desired. By investigating the categories which emerged from the interviews it was then possible to see themes which apply to the two underlying concepts which spurred this research: adopter categories and innovation characteristics.

The Decision-Making Process

It was evident that all informants were very cognizant of how they went about searching for information, which external forces were influential during the process, and how they came to a final purchase decision. Indeed, most informants were very aware of "mistakes" they had made in the past and how they would avoid repeating these mistakes in the future.

"I bought what I thought had good specifications for the money. Which I don't think is the way to go about finding stereo equipment. But I didn't know too much then "

"And I just listened to what the salesperson said and bought it there. I mean, but now I would know better."

The majority reported a very independent process with little external influence on actual purchase.

"My friend reinforced what I already felt about it. The decision to buy was totally mine.'

External influence tended to manifest itself during the search process. Many reported relying on experience with a friend's product prior to deciding to purchase one for themselves. Additionally, many reported utilizing existing literature as a reference guide before entering a store to get hands-on experience. Few reported relying on in-store help for advice. Rather, the in-store advice which was received was discounted as biased by most of the informants. In fact, one reported utilizing stores merely to see and hear the actual products prior to purchasing through a discount mail-order catalog.

"I had a chance to play around with his CD player a little bit before I was really even in the market."

"I talked to several of my friends who had computers, some who just use them and a couple of them who are actually in computer science."

"No, in fact, if the store's advice had influenced my decision, it would have influenced it negatively."

"I try to find as much information as I can before I even get ready to purchase - along with that I'll go to the stores just to look and get a feel for the things. But when I finally get ready to buy, I order through the mail because you can get things so much cheaper."

Although final purchases were sometimes described as impulsive, none omitted a fairly lengthy search process.

"I'd been thinking about getting a boom box for a long time and had been looking, but I wasn't sure when I should get it. And I thought - well, I'm going to need one for the summer - and I need one right now - so I ran out to the store and got one.'

"I got to the point where I just said - all right, I'm going to make myself buy a TV. I'm going to do it."

"I agonized and agonized over spending the money. And I finally just said to myself just do it. So, I did."

Indeed, there was a great deal of similarity in the process across informants and across products. Each informant searched for information, either through literature or one's peers, followed by in-store experience with the product, with a final decision to purchase. This seems to be an effort on the individuals' part to achieve trialability, albeit somewhat limited, before committing to the purchase of basically high-expense, high-risk items. Delays can occur at any point, most often due to a lack of available funds, a lack of need at a given point in time, or an expectation of a future sale or promotion.

Cost-Benefit Analysis

Another interesting, yet not surprising, cause of purchase delay was the search for particular features. Most of the informants reported that there were features which were absolutely essential before they would commit to a purchase. This most often resulted in sacrificing features of lesser importance. This willingness to give up some relatively unimportant features also manifested itself in financial terms.

"I had to have a tape counter that read out in real time. My old deck had that and I loved it. I figured any replacement I got would have to have that - there were two or three things I gave up that were really minor."

"It had to have random shuffle play. Absolutely. I had to sacrifice some other things in order to get that."

"I'd been shopping around a little bit and looking at different places to get the best price - or, rather, to Bet the best price with the best features that I wanted."

This cost-benefit analysis approach was also a determinant of purchase delay of desired items. In fact, most informants would initially give strictly financial reasons for waiting to buy particular products. Common initial reasons were that the products were "too expensive", that the individual "couldn't afford them" or "didn't have that kind of money right now". However, the informants themselves would talk their way out of the easy answer into a more complex decision to wait.

"See, it's funny, because, to tell you the truth - any of these things I really wanted to buy right now - if I really wanted to, I could."

"I would use it so infrequently that it just isn't worth the money. If they came down in price, but I still didn't have time to use it, I guess I'd wait. But if I had the time and they were still expensive, I'd definitely buy one."

The majority of informants realized through discussion that there were deeper, underlying reasons why they were waiting until a future point in time to purchase these items.

Future Expectations

One major reason given for a purchase delay was an expectation of something occurring in the future which would make the purchase more satisfactory. This expectation often regarded the informant himself. Many were waiting for a new phase of life before purchasing new or additional equipment.

"Because the thing that I'd be waiting for is getting my own apartment. You know, after I graduate and get myself established I'll start, you know, stocking up."

"Once I move up out of the student level of society into the working force - that's when all that will happen."

"I might move and fir d a room that a portable TV would be handy in, I don't know. Same for a cordless Phone."

"Maybe when I am gone a lot, and I plan to be, then it would be different and I'd need an answering machine - hey re so convenient. But right now it just wouldn't make any sense."

"I want a VCR, but I'm just trying to save my money to make it last as long as I can so I can finish my novel. Because, to me, having time to work on my novel is more important right now than having the choice of watching movies or any of that kind of stuff."

Another way future expectations played a part in the decision-making process was related to the products. As previously mentioned, Holak, Lehmann, and Sultan (1987) found that expectations of technological improvement were positively related to delayed intention to purchase, but did not find such a relationship with price reduction expectations. However; these individuals mentioned both types of expectations quite frequently.

"HDTV isn't available yet, but when it is it's going to be really expensive. I'm probably going to go for it, though, when it's within reach - although I'll want to wait for companies to introduce new features to it. I definitely won't buy the first generation HDTV."

"And there were a couple of things that made me wait. One, I was waiting for the prices to come down. Two, with any new technology you don't want to buy the first thing that comes out because there are certain bugs and certain other features that are added, and so forth."

Finally, the necessity for packaged or linked product purchases, and the price and availability of related software were also factors in delay of purchase.

"The laser discs themselves are really expensive too."

"If I bought a TV it would be with the laser disc player. But laser discs are still a somewhat new format and there's nowhere near the selection of movies like with videos. But, you know, once the technology's caught on and the price comes down and they come out with more movies, then that would look mare desirable."

"When the time comes and I do get a computer I'll definitely get a modem for it, because we've got one at the office and I've found it to be real handy."

Alternative Technologies

One remaining reason many informants gave for waiting was the current existence of cheaper alternatives, or access to a product without self-purchase.

"But the fact that I'm waiting until my first one completely conks tells you something. I'll probably end up buying one, but not until I have to."

"A laser disc player would be nice, but since I have a VCR I don't know how much use I'd really have for that."

"There's always a computer I can use somewhere. Either at a business, or at school, or anything like that."

This existence of alternatives seems to point to Rogers' innovation characteristic called relative advantage. Another reoccurring characteristic is compatibility with existing needs.

Non-Adoption

The previously discussed cost-benefit analysis approach is particularly obvious in discussion of products which are not desired at all. Many responses to depth probes regarding the reason one did not desire a product could be traced back to some type of cost-benefit analysis on the part of the informant. It was a perceived lack of benefits which was the main contributor to lack of desire.

"I just couldn't bring myself to spend the kind of money they wanted for the quality of sound that they deliver."

"The only benefit I can see for a car phone is for someone to get a hold of me in some work-related capacity. And to be honest with you, I'd rather not be bothered."

"Video game players are really novel at first, but then you get bored with them. After you've figured them out. A lot of electronic products are like that. They're fun to work with at first, and then . . ."

"I guess I don't have enough uses for a computer to make it worth the money.'

Philosophical Opposition

Other reasons given for not wanting particular products had an underlying philosophy attached to them.

"I just don't like to get in the habit of watching TV. I was kind of raised that way.

"I'd become a couch potato - and one day you wake up and you're 60 years old and what have you done with your life?"

"So many people have the stupid things now. I mean, eventually, people are never going to have two-way conversations on the phone anymore."

"I object to (boom boxes) aesthetically - I guess I view it kind of like an invasion of my privacy. I guess I just object to them in principle."

"I don't take snapshots because I just think it's dumb to try to preserve the past."

"I just don't get into listening to music while I'm walking around outside. I like to know what's going on around me."

"I am philosophically opposed to these for two reasons. One, they're unsafe. And two, it's sort of like a technological version of walking around with your nose up in the air. I don't like them, I hate them, they bother me."

These are examples of a lack of compatibility with existing values.

Poor Quality

One final, very simple reason given for lack of desire for a given product was a perceived lack of quality. '

"I don't like boom boxes. They're just an abomination."

"My parents had a cordless phone and it never worked very well."

Given the tendency to pin non-adoption on personality characteristics, this is particularly important. Marketers must come to terms with the fact that some products do not meet the standards of consumers, even if they do fit their values or needs.

CONCLUSION

To summarize, the overriding characteristics of innovations which seemed to shape the decision-making processes of these nine individuals differed depending on the decision outcome. For actual purchases, trialability seemed to be the most salient part of the overall process. All of the informants attempted product trial either through in-store searching or experience with a friend's acquisition. Delay of purchase, however, tended to be caused mainly by a lack of compatibility with existing needs or a lack of relative advantage over some alternative product, with future expectations playing a major role in the process. For product non-adoption, compatibility with existing values was a key factor, along with a simple lack of quality of the product. Across each of the three decision-making categories was a very clear-cut, rational cost-benefit analysis. At no point in any of the interviews was observability or complexity mentioned as contributing to a decision. This does not mean that they are not factors in the decision-making process. Rather, it means either that these individuals did not consider them to be of much importance in their decisions, or chose not to share them as important factors.

These individuals were, admittedly, a nonrandomized group consisting of fairly enthusiastic volunteers. An obvious extension of this research would be to conduct additional interviews with a more average type of consumer. However, the very fact that these informants were somewhat specialized in their product experience leads to the conclusion that categorizing individuals' innovativeness based on adoption of a single product is overly simplified. Although these informants had similar underlying decision-making processes, they differed drastically in which products applied to the three categories. In other words, one informant would never consider purchasing digital audio tape while another listed that as his next purchase priority. Similarly, one individual hated answering machines while another had one and loved it. The point is that predicting attitudes and perceptions based on ownership of a given product, or membership within a traditional adopter category would seem to be difficult.

It is necessary for diffusion researchers to begin defining individuals' innovativeness based on ownership of and attitude, towards a range of products. The previously described body of research which focuses on subjective perceptions of innovations is an essential step in this effort. Researchers have realized for a long time that the study of consumer behavior is difficult. The interviews reported in this paper represent only a scratch on the surface of the complex interaction between the personalities of individuals, their perceptions of the products, and the decision of whether or not to adopt a given innovation. Continued research which focuses on this interaction is essential for a deeper understanding of the diffusion process.

REFERENCES

Dickerson, Mary Dee and James W. Gentry (1983), "Characteristics of Adopters and Non-Adopters of Home Computers," Journal of Consumer Research, 10 (September), 225-235.

Feick, Lawrence F. and Linda L. Price (1987), 'The Market Maven: A Diffuser of Marketplace Information," Journal of Marketing, 51 (January), 83-97.

Fliegel, Frederick C. and Joseph E. Kivlin (1966), "Attributes of Innovations as Factors in Diffusion," American Journal of Sociology, 72, 235 -248.

Gatignon, Hubert and Thomas S. Robertson (1985), "A Propositional Inventory for New Diffusion Research," Journal of Consumer Research, 11 (March), 849-867.

Glaser, Barney G. and Anselm L. Strauss (1967), The Discovery of Grounded Theory: Strategies for Qualitative Research, Chicago: Aldine.

Heany, Donald F. (1983), "Degrees of Product Innovation," Journal of Business Strategy, 3 (Spring), 3-14.

Holak, Susan L., Donald R. Lehmann, and Fareena Sultan (1987), 'The Role of Expectations in the Adoption of Innovative Consumer Durables: Some Preliminary Evidence," Journal of Retailing, 63 (3), 243-259.

Lincoln, Yvonna S. and Egon G. Guba (1985), Naturalistic Inquiry, Beverly Hills, CA: Sage.

Miles, Matthew B. and A. Michael Huberman (1984), Qualitative Data Analysis: A Sourcebook for New Methods, Beverly Hills, CA: Sage.

Norton, John A. and Frank M. Bass (1987), "A Diffusion Theory Model of Adoption and Substitution for Successive Generations of High-Technology Products," Management Science, 33 (9), 1069-1086.

Ostlund, Lyman E. (1974), "Perceived Innovation Attributes as Predictors of Innovativeness," Journal of Consumer Research, 1 (September), 23 -29.

Robertson, Thomas S. (1971), Innovative Behavior and Communication, New York: Holt, Rinehart & Winston.

Rogers, Everett M. (1983), Diffusion of Innovations, New York: The Free Press.

Wilton, Peter C. and Edgar A. Pessemier (1981), "Forecasting the Ultimate Acceptance of an Innovation: the Effects of Information," Journal of Consumer Research, 8 (September), 162-171.

----------------------------------------