In the introduction of Human Computer Interaction by Dix et al. (2004), the authors explain that “computers and related devices have to be designed with an understanding that people with specific tasks in mind will want to use them in a way that is seamless with respect to their everyday work.” (p. 2). The authors argue that Human Computer Interaction is important within Computer Science education, and claim that “the human, the user, is, after all, the one whom computer systems are designed to assist.” (p. 12). In chapter 1, Dix et al. explain that humans are limited in their information processing ability, which is important when considering design. (p. 11).

From a human standpoint, information travels through three stages: perception, storage, and processing/ application. The perception stage involves input-output channels, from which a human receives a computer’s output. The most important of the input channels for humans are sight, hearing, and touch; one looks at the screen, listens to beeps or other noises, and touches the mouse or keyboard in order to obtain information. (p. 13). When designing a computer, one must be cognizant of how these senses work. When considering visual appearance, one must understand the strengths and weaknesses of the human eye and how it perceives size, depth, brightness, and color. (p. 14 – 23). To ensure that audio is effective, one must know the limits of the human ear, and how we decide what sounds we pay attention to (p. 23 – 24). Finally, one must consider touch, or “haptic perception,” and movement when designing computers. (p. 25- 26).

The next stage through which information travels is memory. Once information passes through the sensory system, it enters into sensory memory, which acts as buffer through which certain stimuli is selected. From there, it is moved to short-term memory, also known as working memory, where it is briefly stored. Information can be accessed and lost very rapidly within short-term memory; it is a place in which information is consciously accessed, examined, and moved along or simply decayed. Once information has passed through the short-term memory, it is sent to long-term memory, where it is stored in the cortex as semantic or episodic information until activated through recall. (p. 27- 34).

The final stage is recall and subsequent manipulation of information, or thinking, which sets humans apart from animals and artificial intelligence. (p. 40). From an HCI perspective, thinking is broken down into categories of reasoning, “the process by which we use the knowledge we have to draw conclusions or infer something new about the domain of interest,” (p. 40) and problem-solving, “the process of finding a solution to an unfamiliar task, using the knowledge we have.” (p. 43).

However, human thought is prone to errors, as a result of changes in skills or incorrect mental models of situations. (p. 49). Additionally, humans are subject to intentional and unintentional emotional responses, unlike machines. Thus, in order to build a computer that is a successful and usable tool, one must account for the way humans perceive, interact with, and are influenced by information—if one does not take the human user into account, a machine is apt to be unsuitable for efficient use.