Plans and Situated Actions: The Problem of Human-Machine Communication
Source: https://archive.org/details/plansandsituated0000such ↗
Lucy Suchman was an anthropologist embedded at Xerox PARC who filmed people trying to use a photocopier and discovered something that shattered a core assumption of both AI and interface design: people do not follow plans.
They improvise constantly, adapting to circumstances as they unfold.
This ethnographic finding demolished the symbolic AI paradigm that assumed human action was essentially plan execution, and it redirected a generation of interface designers toward contextual, situated design.
The implications extend well beyond HCI — product managers who believe users follow the happy path in their journey maps are making the same mistake Suchman identified forty years ago.
The book is also an early, rigorous argument for why building products requires observing what people actually do, not what they say they do.
Central argument
Suchman argues that human action is not the execution of pre-formed plans but is instead improvised in response to concrete, unfolding circumstances — what she calls 'situated action.' Her ethnographic study of people using a Xerox photocopier demonstrates that the machine's interface was designed around a planning model of human behavior that simply does not match how people actually act. The book directly challenges the symbolic AI assumption that cognition consists of manipulating abstract representations, and argues instead that meaning and action only become intelligible within their specific social and material context.
Critique
Suchman's framework, built on close observation of small, bounded interactions with a single device, risks overgeneralizing from a specific ethnographic setting to a universal claim about human action. A thoughtful critic could argue that plans do real causal work in certain domains — surgery, air traffic control, complex engineering — and that her dichotomy between 'plans' and 'situated action' may itself be too clean, obscuring how people use plans as flexible resources rather than rigid scripts. Her work also predates ubiquitous computing and learned user behavior at scale, leaving open the question of whether decades of product habituation have changed the degree to which some users do internalize and follow structured flows.
Why it matters for product
CPOs who commission journey maps, write user stories around happy paths, or design onboarding flows based on assumed sequential behavior are institutionalizing exactly the planning fallacy Suchman identified — their artifacts describe how the product team imagines use, not how use actually unfolds. This has direct consequences for discovery practice: generative research must include observation of actual behavior in context, not just interview-based accounts of what users intend or recall doing. It also has organizational implications — product teams structured around funnel metrics and conversion rates at each 'step' are measuring conformance to a planned path that most users are already deviating from.