Diffusion of Innovations: Rogers' Theory
The single most examined topic in the Extension paper. The four elements, the five attributes, the decision process and the curve.
What diffusion is
Everett M. Rogers defined diffusion as the process by which an innovation is communicated through certain channels over time among the members of a social system. That definition is worth memorising word for word, because the four elements the examiner asks for are simply its four nouns.
Diffusion of Innovations was first published in 1962 and ran to five editions. Diffusion is a special type of communication, one concerned with new ideas, and therefore carrying a degree of uncertainty that ordinary communication does not.
The four elements
- Innovation. An idea, practice or object perceived as new by the individual. Perceived is the operative word: it does not matter how old the idea objectively is.
- Communication channels. The means by which messages pass. Mass media are efficient at creating awareness; interpersonal channels are what actually persuade.
- Time. Present in the innovation-decision process, in innovativeness, and in the rate of adoption. Rogers noted that time is a variable most social science research ignores.
- Social system. A set of interrelated units engaged in joint problem solving. Its norms, its opinion leaders and its change agents shape everything else.
The five attributes of an innovation
These five explain most of the variance in rate of adoption, and they are the most frequently asked part of the whole theory.
- Relative advantage. The degree to which the innovation is seen as better than what it replaces. Positively related to adoption.
- Compatibility. Consistency with existing values, past experience and needs. Positively related.
- Complexity. Perceived difficulty of understanding and use. Negatively related, and the only one of the five that is.
- Trialability. Whether it can be experimented with on a limited basis. Positively related. This is why a farmer will try a new variety on one acre first.
- Observability. Whether the results are visible to others. Positively related, and the reason result demonstrations work.
The innovation-decision process
Five stages, in order:
- Knowledge. The person becomes aware the innovation exists.
- Persuasion. A favourable or unfavourable attitude forms.
- Decision. Activities leading to adoption or rejection.
- Implementation. The innovation is put to use.
- Confirmation. The person seeks reinforcement, and may reverse the decision.
Note the distinction the examiner likes: discontinuance at the confirmation stage is not the same as rejection at the decision stage. Discontinuance is either replacement, where something better came along, or disenchantment, where the innovation disappointed.
Adopter categories
Rogers divided adopters on the basis of innovativeness, using the normal curve and standard deviations from the mean adoption time:
| Category | Share | Character |
|---|---|---|
| Innovators | 2.5% | Venturesome, cosmopolite, able to absorb the loss of a failure |
| Early adopters | 13.5% | Respectable, localite, the opinion leaders others watch |
| Early majority | 34% | Deliberate, adopt just before the average member |
| Late majority | 34% | Sceptical, adopt under peer or economic pressure |
| Laggards | 16% | Traditional, the point of reference is the past |
Early adopters, not innovators, are the category extension should target. Innovators are often too far ahead of the system to be credible models for it.
The adoption curve
Plotted as adopters per time period the distribution is normal and bell-shaped. Plotted cumulatively it becomes the familiar S-shaped curve: slow at first while only innovators and early adopters are involved, steep through the two majorities, and flattening as only laggards remain.
The rate of adoption is measured as the number of members of the system who adopt in a given period. Where an innovation scores well on the five attributes, the S-curve is steeper.
Diffusion and communication compared
| Communication | Diffusion |
|---|---|
| Any message | Only messages about new ideas |
| Little uncertainty | Uncertainty is inherent |
| Source, message, channel, receiver, effect | Innovation, channel, time, social system |
| Change in knowledge or attitude | Adoption or rejection is the outcome |
Points to carry into the exam
The lines from this topic that recur in the paper.
- Rogers' definition has four nouns and they are the four elements. Learn it verbatim.
- Complexity is the only attribute negatively related to adoption.
- Adopter percentages: 2.5, 13.5, 34, 34, 16. They must add to 100.
- Early adopters are the opinion leaders and the right target for extension, not innovators.
- Discontinuance is at confirmation; rejection is at decision. Two types of discontinuance: replacement and disenchantment.
- Cumulative adoption gives the S-curve; per-period adoption gives the bell curve.