HCC class lecture 24 comments

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HCC classlecture 24 comments
John Canny4/20/05
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Administrivia
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Diffusion

• The mechanism whereby innovations propagate in a
  society.
• Diffusion happens on social networks. It depends
  on both internal factors (attitudes and behavior
  of the actors) and structural factors i.e. the
  structure of the network.

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Diffusion

• Diffusion is not automatic. Many famous ideas
  did not diffuse quickly, or not at all. Examples
• Boiling water for sanitation Failed in a
  Peruvian village because it contravened custom.
• Citrus fruits for scurvy Took many, many years
  in spite of apparently strong evidence.
• Dvorak keyboard Clearly superior to QWERTY but
  inertia seems to prevent adoption.

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Elements of Diffusion

• The innovation an idea, thing or practice that
  is perceived as new.
• Communication Channels Means or media through
  which information about the innovation
  propagates.
• Time Diffusion is a dynamic process.
• A Social System We are often interested in
  diffusion within particular social groups. Social
  networks are central also.

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Adoption categories

• Innovator/Early Adopter The first 10-15 of
  adopters.
• Early Majority The remainder of the first half
  of adopters (15 to 50th percentile).
• Late Majority The second half of adopters
  (ignoring laggards)
• Laggards The last 10-15 of adopters.

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Innovations

• Technological innovations
• Hardware Presence and diffusion are obvious.
  Physical form dictates minimum costs, but various
  strategies can mitigate this shaver-and-blades
  strategy in printers, projectors, cell phones,
  DVRs.
• Software Includes ideas Marxism, religions,
  news, rumors, just-in-time manufacturing, etc.
  Hard to track, adoption is often unclear.

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Innovations

• Perceived advantage Is important. It includes
  prestige as well as objective advantage.
• Compatibility Must be compatible with existing
  practice and values.
• Complexity Perceived difficulty and work to
  use it.
• Trialability Easy on-ramp allows users to try
  it and dispel some of their apprehensions.
• Observability Can others see the results and
  assess them?

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Communication channels

• Mass media People learn about innovations
  through mass media, but most will not adopt
  (innovators may).
• Scientific evidence May be more convincing, but
  still not enough (consumers seem to know a lot
  about how science is done).
• Interpersonal channels The most important
  channel for most people. Adoption for many
  happens when they know others whom they trust
  have adopted.

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Heterophily and Homophily

• Homophily the degree to which individuals who
  interact are similar in beliefs, education,
  social status.
• Heterophily the degree of difference in these
  attributes.
• Innovations move rapidly in homophilous networks.
  Users trust their peers, and see their own social
  role in terms of technologies that peers adopt.
• However, Heterophily is essential for diffusion
  throughout a large social group. The group will
  contain many homophilous groups, and the adoption
  categories (innovator etc.) are often in
  different groups.

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Innovation/Decision

• Knowledge
• Persuasion
• Decision
• Implementation
• Confirmation

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Innovation/Decision

• Knowledge User learns about innovation.
• Persuasion
• Decision
• Implementation
• Confirmation

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Innovation/Decision

• Knowledge User learns about innovation.
• Persuasion User forms favorable attitude.
• Decision
• Implementation
• Confirmation

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Innovation/Decision

• Knowledge User learns about innovation.
• Persuasion User forms favorable attitude.
• Decision User decides to adopt.
• Implementation
• Confirmation

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Innovation/Decision

• Knowledge User learns about innovation.
• Persuasion User forms favorable attitude.
• Decision User decides to adopt.
• Implementation User actually puts innovation to
  use.
• Confirmation

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Innovation/Decision

• Knowledge User learns about innovation.
• Persuasion User forms favorable attitude.
• Decision User decides to adopt.
• Implementation User actually puts innovation to
  use.
• Confirmation User seeks reinforcement of their
  decision.

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Social Systems

• Social structure Includes formal social
  structures such as bureaucracies, government
  hierarchies, caste systems, understood social
  roles. These structures involve influence/power
  relationships and exchange.
• Communication structure How people actually
  communicate in the network. This is less studied
  in traditional diffusion theory, but is now much
  more active because electronic networks are
  observable.

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Opinion leaders and change agents

• Opinion leaders Individuals who influence others
  behavior tribal elders, sages, columnists,
  activists. Typically follow community norms,
  rather than lead them.
• Change agents Individuals who attempt to
  influence the system toward change. Often they
  are outsiders. A good strategy for them is to
  marshall the influence of opinion leaders, since
  their own influence is likely to be limited.

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Consequences

• Desirable/Undesirable Poor implementation may
  cause the innovation to fail or backfire (e.g.
  deforestation/desertification).
• Direct/Indirect Innovations have many
  second-order effects that may be hard to track.
  Most technical innovations are more accessible to
  the rich and well-educated and tend to increase
  social stratification.
• Anticipated/Unanticipated Indirect affects may
  be anticipated or not. Many are impossible to
  predict, especially since technology adoption
  often changes social practices in the long term.

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Network effects

• The key to successful diffusion is the conversion
  of opinion leaders. Once a critical mass of
  opinion leaders convert, the innovation usually
  takes off rapidly.
• Densely-connected graphs or cliques are very
  important. Converting a few members in a clique
  makes the innovation seem popular because of
  individuals who have several neighbors in the
  clique.

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Two-step flow model

• Researchers originally believed that the mass
  media influenced individuals opinions directly
  (the hypodermic needle model).
• This model was gradually displaced by the
  two-step flow model where ideas flow first from
  the media to opinion leaders and then to the
  general public. But the opinion leaders may exert
  their own or the communitys views first.

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Measuring Opinion leadership

• Sociometric Ask users who influenced them.
• Informant ratings Ask a smaller but
  well-informed set of users about opinion leaders.
  
• Self-designation Ask the potential leaders
  themselves if they believe they have influence.
• Observation Direct measurement of communication
  and adoption actions in a network. The most
  reliable, but traditionally expensive method.

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Opinion leaders

• External communication Opinion leaders have
  greater exposure to external communication
  (media, network).
• Accessibility They are accessible and
  participate extensively in social activities.
• Status They generally have high social status.
• Innovativeness To be trusted as authorities
  about innovation, they must innovate regularly.

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Other network actors

• The actors in a diffusion network need not be
  people. They can also be
• Corporations e.g. offering of broadband
  services, data services, GPS among telcos.
• States Legislation, taxes, social programs etc.
  follow a particular adoption hierarchy among US
  states.
• Nations Similar phenomena are manifest among
  european states, e.g. adoption of the euro.

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Strength of weak ties.

• Mark Granovetter showed that weak ties (often not
  direct or weak direct ties) are very important
  for certain decisions, like taking a new job.
• These weak ties are often heterophilous, allowing
  the actor to step across traditional boundaries.
• Weak ties do not support much influence, but
  allow crucial information to flow rapidly.

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Individual thresholds

• Network models allow for explanations of adoption
  in terms of personal adoption thresholds the
  fraction of neighbors who have adopted before the
  actor is persuaded to adopt.
• Adoption thresholds vary. They are lowest for
  innovators, higher for early majority etc.
• The threshold model explains the snowballing
  effect of adoption.

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Discussion Topics

• T1 Think about how opinion leadership could be
  measured with the social network methods we
  already discussed.
• T2 What do you think homophily and heterophily
  mean as graph properties? i.e. how could you
  compute them?
• T3 Where does diffusion fit among Vygotskys
  genetic domains?