What Is Interaction?

Interaction, in the context of computing and electrical engineering, refers to the exchange of inputs and outputs between a user and a system, between two or more software processes, or between physical entities in a networked environment. The term is broad by design: it captures the moment-by-moment dialogue through which a person operates a device, the message-passing protocols through which distributed components coordinate, and the force or signal exchanges through which robots and physical systems engage with their environments. The most extensively studied form in computing is human-computer interaction (HCI), which examines how people communicate their intentions to computing systems and how those systems respond in ways that are usable, efficient, and satisfying.

The study of interaction in computing grew out of mid-twentieth century research in cybernetics, cognitive science, and human factors engineering. It became a distinct discipline in the 1980s as personal computers introduced non-expert users to direct manipulation interfaces, making the quality of the human-machine dialogue a practical engineering concern rather than an academic one.

Human-Computer Interaction

Human-computer interaction is defined by ACM SIGCHI as the discipline concerned with the design, evaluation, and implementation of interactive computing systems for human use, along with the study of phenomena surrounding those systems. The interaction loop involves a user forming a goal, translating that goal into system actions through an interface (keyboard, touchscreen, voice command, or gestural input), observing the system's response, and evaluating whether the goal was achieved. Usability, the extent to which a system can be used efficiently, effectively, and satisfyingly by its intended users, is the primary quality metric. Research on human-computer interaction as an engineering discipline spans interface design, accessibility, cognitive load, and the evaluation of both physical and software-mediated interaction artifacts.

Interaction Models and Paradigms

Formal models of interaction provide the theoretical basis for designing and analyzing interactive systems. The model-human processor framework, developed by Card, Moran, and Newell in the 1980s, treats the user as a cognitive processor with measurable cycle times for perceptual, motor, and cognitive operations, enabling quantitative predictions of task completion time. Later frameworks address touch, voice, and multimodal interaction, where multiple input channels are combined simultaneously. The shift from desktop interfaces to embedded systems, wearables, and ambient computing expanded the interaction surface to include gestural, tactile, and environmental signals, requiring models that account for context-awareness and physical embodiment. Proceedings of the ACM on Human-Computer Interaction are a primary venue for empirical and theoretical work on these evolving paradigms.

Interaction in Networked and Distributed Systems

Beyond the single user and device, interaction encompasses the protocols and interfaces through which distributed components, services, and autonomous agents communicate. Application programming interfaces (APIs) define the formal contract for interaction between software modules. In multi-agent systems and robotic teams, interaction includes both explicit communication and implicit coordination through shared environment states. The design of these system-level interactions shares concerns with HCI: latency, reliability, feedback, and error handling all determine whether the interaction achieves its intended purpose.

Applications

Interaction has applications in a wide range of fields, including:

• User interface design for consumer electronics and productivity software
• Accessible technology for users with sensory, cognitive, or motor impairments
• Collaborative systems and computer-supported cooperative work environments
• Human-robot interaction for manufacturing, surgery, and assistive applications
• Natural language processing interfaces and conversational agents
• Interaction design for augmented and virtual reality environments