Not a “unified theory” in the classical sense, but rather an interdisciplinary field that combines computer science, psychology, engineering, and user interface design. The theoretical framework dates back to the early 1970s, with the work of Douglas Engelbart (1968–1970), who invented the mouse and developed the first interactive user interface systems. Academically, the most prominent founders of HCI as a field of study were Stuart Card, Thomas Moran, and Allen Newell of Xerox PARC, who published their famous book The Psychology of Human-Computer Interaction, the first comprehensive theoretical framework for the study of human-computer interaction, in 1983.
This theory focuses on understanding:
1) The interaction of humans with technology: software, hardware, robots.
2) Developing effective user interfaces that reduce errors and increase productivity.
3) Cognitive-psychological functions, such as attention, memory, and learning when interacting with machines.
4) Emotional and social aspects of digital interaction, including interaction with social robots or intelligent systems.