Strength of Weak Ties

(Granovetter)

What is a weak tie?

• Strength of tie as a linear combination• F = Frequency of Contact• E = Emotional intensity• I = Intimacy (mutual confiding)• R = Reciprocal services

lij=w1F+w2E+ w3I+ w4R

• Granovetter leaves exact functional form and weighting “postponed for future empirical work”

Simplification

• For purpose of building theory, ties classified as • “strong”• “weak”• “absent”

Example

A B

S={C,D,E…}

Connection Closure

• If • A is connected to B (strong tie)• A is connected to C (strong tie)• A-B and A-C are independent

• Then• P(B-C | A-B, A-C) = P(A-B)*P(A-C)

• A weaker connection B-C exists with a higher probability

• Common strong ties generate new connections

Cognitive Balance

• Anything short of a positive tie between B and C “would induce psychological strain”

The “Forbidden Triad”• The amount of dissonance

between B and C is proportional to strength of ties A-B and A-C

• If A-B and A-C are strong, triad occurs rarely

• If A-B and A-C are weak, dissonance is low and weak tie B-C can be present

A B

CDissonance

Connections and Similarity

• Newcomb(1961), Friedkin (later)• The stronger the tie connecting two

individuals, the more similar these individuals are

• Thus, if A-B and A-C are strong ties• B is similar to A, C is similar to A

• By transitivity

• B is similar to C

Weak ties and Bridging

• Strong ties are unlikely to be bridges

• Weak ties can bridge distinct groups without interpersonal dissonance

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Local Bridges

• Global bridges (I.e. cutpoints) are unlikely in real networks• Single ties between “clumps” are unlikely

• Local bridges create paths between groups• Local bridge of degree n

• Weak ties allow for more redundancy• Shorter paths

Diffusion

• Weak ties speed up information diffusion• Shorter distances mean faster penetration• More redundancy means wider reach

Weak Ties in Ego Nets

• Burt: look at overall density and redundancy in ego nets (I.e. Structural holes)

• Granovetter: Partition the ego network into three groups:• Strong ties• Weak ties

• Personal ties of the Ego

• Bridging weak ties• Guaranteed to connect ego to outside groups

Empirical Study

• Job search in Boston• Survey asks how applicant found out about

the job opening• If job is found through personal contacts:

• How often does ego see the contact?• Where did the contact get the information?

Hypothesis:

• These with strong ties to ego are more motivated to help find a job

• Weak ties connect to information outside immediate group

• Information gets diffused by long paths

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Result

• 16.7% report strong ties (interact often)• 55.6% report mid-strength

(occasionally)• 27.8% interact rarely

• Often > twice a week• Occasionally > once a year• Rarely < once a year

Questions

• Are these gradations sufficient?• Do we need greater granularity?

Questions

• What is possible distribution of overall tie strength in the network? • Skewed normal?• Maybe a power law?

• We know that degree distributions tend to power laws

• Does it affect what ties have higher probability of being used for job search?

More results

• Source of job information:• 39.1%: direct from employer• 45.3%: one intermediary• 12.5%: two• 3.1%: > 2

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Leadership and weak ties

• High number of strong ties in the in-group generally means less ties to the out-group• Related to limited cognitive capacity?

• Societies characterized by tight in-groups emerge local leaders, but each in-group acts on its own

Weak ties in politics

• Trust in a leader a function of having a bridging tie from ego to leader • (even a very weak one)

Weak ties in politics

• Politicians must cultivate weak ties near election time• “kissing babies”• Name recognition

• Strong ties are required to get things done• Committee work