Many long-standing problems in the online communities literature, such as group- think, silent majorities, bystander effects, and collective action failures, can all be traced back to a first-mover disadvantage: it is risky to be the first to speak up. Isolated individuals deciding whether or not to raise a diverging perspective or to initiate a collective action effort often cannot be sure whether others would welcome it, and back them up. As a result, people may fail to surface an opinion even though it is privately held by many, refrain from publicly speaking up against misbehavior even though many privately think it is unacceptable, and fail to act in response to concerns that are not voiced publicly but are widespread. First mover disadvantages don't just impede one-time prosocial actions; they also act as a brake on positive norm change.

This dissertation proposes that designers of online communities can lower these first-mover disadvantages through a design pattern that I call an action escrow–a mechanism where people deposit a socially risky action with an intermediary system that only executes the action if a prespecified trigger criterion is met. For example, an action escrow for encouraging authentic opinions might allow a user to place a comment into escrow with the instruction that it be posted publicly only if the escrow system receives similar comments from two other users. Although action escrows are not new–they feature in some existing systems and are inspired by traditional escrows in legal and economic scholarship–this dissertation gives name to this loosely applied pattern and formalizes its scope, and utility for addressing persistent challenges in online communities.

To show that action escrows are effective, I introduce two systems, Nooks and Empathosphere, each of which advances action escrows further as an approach to addressing first-mover disadvantages. Nooks shows how action escrows can lower first-mover disadvantages in bringing up new topics in a community. Empathosphere shows how action escrows can be applied to give communities translucence into privately held opinions. Through a field deployment of Nooks and an experimental evaluation of Empathosphere, I show how action escrows do indeed address first-mover disadvantages and by doing so, encourage prosocial action, reveal suppressed perspectives, and improve inclusion.

To inform future implementations, I describe a broader design space of action escrows, outline the limitations and risks of introducing action escrows into online communities, identify how these risks can be mitigated, and synthesize broader opportunities for escrow mechanisms to address long-standing challenges in HCI.

As activities in online communities increasingly flow beyond digital boundaries to shape political movements, social institutions, and civic discourse, I envision a future where thoughtfully designed mechanisms can re-engage dormant voices, counter false polarization, and foster inclusion, in digital spaces and ultimately in broader society.

106 pages

Thesis Committee:
Geoff Kaufman (Co-Chair, CMU)
Chinmay Kulkarni (Co-Chair, Microsoft AI)
Jason Hong
Karrie Karahalios (University of Illinois Urbana-Champaign)

Brad A. Myers, Head, Human-Computer Interaction Institute
Martial Hebert, Dean, School of Computer Science

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