Throughout human history it has been technological innovation that has expanded the bounds of human capability (Forsythe et al., 2014). Yet, as technology has grown increasingly complex, our achievable limits are no longer determined by technology, but instead by human cognitive and physical capacities, in concert with our abilities to cope with the ensuing stresses. Further technological advances will necessitate thorough consideration of the human dimension in the design of systems, products and services as well as greater understanding of the brain and how its operations shape our capabilities and experiences. Human information processing and cognitive psychology are becoming an increasingly important area in quality, safety and risk management by allowing us to predict human performance within systems, understand how people solve problems, and why errors occur. The principles of cognitive psychology are used to model human-system interactions, design various hospital information systems, workstations, and equipment controls, displays, labels, and symbols. Wickens and Carswell (2006) argued that there is a plethora of situations in which healthcare providers interact with systems, perceive selected information, transform information into different forms, take actions based on the perceived and transformed information, process the feedback from actions, and assess the effect of actions on the environment. These transformations can be cognitively demanding, time-consuming and may be the source of errors. There is a growing body of evidence that working memory constraints, sensory limitations, perceptual confusion, the level of knowledge and experience, heuristics and biases, long-term memory organization, attention, physical capabilities, risk perceptions, risk attitudes, and internal performance shaping factors have significant impact on human performance in complex systems. A model of human information processing shown below provides a simple framework for analyzing a series of processing stages or mental operations that typically take place when humans interact with systems or perform tasks.
According to Wickens and Carswell (2006), stimuli or events in the environment are first sensed and attended by our sensory system. Perceived information is provided with some meaningful interpretation based on memory of past experiences. It should be noted that that sensation and perception are two completely different concepts and from the large array of sensory information received by our senses only a smaller amount may be actually perceived. We can respond directly to the perceived information by making decision, selecting appropriate course of action and executing action. Alternatively, the perceived information may be stored temporarily for further processing in the working memory that is closely related to our long-term memory. Executed response often generates feedback, which is then sensed and attended by our senses to complete the closed-loop cycle. Human attention is a limited resource and it plays two vital roles in the information processing sequence. As a selective agent, it filters and limits the amount of information that will be actually perceived for further processing. As a task management agent, it constrains what tasks or mental operations can be performed concurrently. Attentional resources required to perform one cognitively difficult and demanding task may not allow performing concurrent tasks. Unless the task is well practiced, straightforward and routine, it is very difficult for us to do more than one thing at a time.
Working memory is an attention-demanding cognitive system with a limited capacity that we use to briefly hold new information or encode it into long-term memory. We also use working memory to process and manipulate information including examining, evaluating, transforming, and comparing different mental representations. Retrieval of information from the working memory is conscious, slow and effortful. The transient characteristic of working memory has been repeatedly demonstrated through numerous experiments suggesting that in the absence of continuous rehearsal, hardly any information is retained beyond 10 to 15 seconds. It is not surprising that faster decay occurs when more items are held in working memory. Decay over time may be influenced by other factors such as interference from similar information learned at another time. The amount of information that working memory can hold is also limited. It is generally accepted that the maximum capacity of working memory is between five and nine items when full attention is allocated for rehearsal. The maximum number of items that can be recalled correctly is often referred to as the memory span. It is clear that the concept of working memory and understanding of its limitations has significant implications for error prevention strategies and design of healthcare systems and processes. Long-term memory is a system with seemingly unlimited capacity for encoding, permanent storage and retrieval of vast amount of factual information about the world, personal life experiences and knowledge about specific events in time. Retrieval of information from the long-term memory is fast and without cognitive effort; however, information stored in long-term memory is not always fully available or accessible for retrieval. Knowledge and information in long-term memory is often stored in terms of general concepts and pieces of information known as schemas or mental models. Schemas contain knowledge that is structured in a practical and functional way so that it can be retrieved in a ready-to-use fashion and is built up from previous experience of similar situations. On a daily basis, people rely on implicit memory in the form of procedural memory to perform tasks such as riding a bicycle or driving a car without consciously thinking about it.
Forsythe et al. (2014) argued that the strengths and weaknesses of the human brain are most apparent in the conscious thought processes that underlie everyday problem solving. Arguably the greatest strength of the human brain is its seemingly endless capacity to store information it has attained during a lifetime that, while often not perfect, can be later retrieved and efficiently applied in solving current problems. The most prominent weakness of the human brain is its limited capacity for conscious awareness even though the vast majority of information processing occurs at unconscious level within the brain. Unconscious processes may impact our decisions and affect our reactions to different situations, but we generally have no awareness of what information has been processed or how that information has influenced our conscious thought processes. The successful operation of the brain requires that many different elements operate in coordination with one another. Consequently, it is relatively easy to observe how the various disturbances and emotionally significant events can upset the balance and severely limit our capacity to access our memory stores. As outlined in the figure below, there are many mechanisms we use to cope with the inherent weaknesses of the human brain. We hardly ever think about these mechanisms because they are embedded in our everyday behaviour and, in some cases, institutionalized within the culture.