Network Experiments & Interventions

1) Assessing Peer Effects1) Manipulate networks to force connectivity to be exogenous

1) Roommate studies2) Natural Experiments

2) Manipulate exposure over existing networks1) Popularity2) Voter Turnout

2) Interventions: Use networks to affect change1) Valente’s 4 elements of network intervention2) Exemplars

3) Network interference in “standard” experiments4) What we’re ignoring: small group stuff

1) network exchange experiments2) Transmission evolution experiments

Network Experiments & InterventionsIntro

Shalizi & Thomas: PI is *generally* confounded

General fear of confounding by unobserved selection features has pushed interest in network experiments. How to make a social relation exogenous?

Roommates assigned randomly within gender, & self-reported smoking, study-style & messiness.

No evidence of pair-similarity based on this sorting (i.e. all evidence suggests randomness is real)

Network Experiments & InterventionsExogenous networks (W)

Assume that one’s one GPA is a function of own ability & peer ability and GPA

Network Experiments & InterventionsExogenous networks (W)

Assume that one’s one GPA is a function of own ability & peer ability and GPA…results suggest a positive effect.

Similar effects on social outcomes (joining a fraternity, etc.)…

Network Experiments & InterventionsExogenous networks (W)

Network Experiments & InterventionsExogenous networks (W)

Note follow-up work (by Salganik & Watts) suggests the effects are weak and not long lasting

Network Experiments & InterventionsExogenous networks (W)

Network Experiments & InterventionsExogenous networks (W)

SEPTEMBER 2010 VOL 329 SCIENCE

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous networks (W): Issues with experimental assignment

Sharique Hassan

Network Experiments & InterventionsExogenous Behavior (Y)

4 types of interventions:1) Individuals

1) Finding opinion leaders or flow blocking nodes that play a key role in the network process. usually some centrality score, or an adaptive algorithm. Here highlighted “keyplayer” nodes.

2) Segmentation3) Induction4) Alteration

Network Experiments & InterventionsExogenous Behavior (Y)

4 types of interventions:1) Individuals2) Segmentation

1) Use communities to break the groups into parts, treat some use others as controls.

3) Induction4) Alteration

Network Experiments & InterventionsExogenous Behavior (Y)

4 types of interventions:1) Individuals2) Segmentation3) Induction

1) Enhance relations & communication4) Alteration

Network Experiments & InterventionsExogenous Behavior (Y)

4 types of interventions:1) Individuals2) Segmentation3) Induction4) Alteration

1) Programs that seek to change the shape of the network, add/remove ties or nodes

Network Experiments & InterventionsExogenous Behavior (Y)

Network Experiments & InterventionsExogenous Behavior (Y)

Exploit the “Friendship Paradox” idea…