20.2 Human Factors and Ergonomics

Understanding Human Factors and Ergonomics in Cognitive Psychology

Human factors and ergonomics definition

Human factors and ergonomics (HF&E) is the study of how humans interact with systems, tools, and environments. Rather than forcing people to adapt to poorly designed systems, HF&E flips the script: it adapts the system to fit human capabilities and limitations.

This is a multidisciplinary field that draws on cognitive psychology, engineering, and design. The dual goal is always the same: improve human well-being (safety, comfort, reduced error) and system performance (efficiency, reliability, output) at the same time. These two goals aren't in tension. A system designed around how people actually think and move tends to perform better on every measure.

Cognitive factors in human-machine interaction

Every time you interact with a machine or interface, several cognitive processes are running simultaneously. Understanding which ones matter most helps designers build systems that work with the brain instead of against it.

• Attention determines what information you focus on and what you filter out. In a cockpit, pilots must attend to critical instruments while ignoring dozens of less relevant ones. Poor display design can cause pilots to miss vital readings.
• Perception governs how you interpret sensory input from an interface. Dashboard warning lights, for example, rely on color, brightness, and position to convey urgency. If a critical alert looks too similar to a routine notification, it may go unnoticed.
• Memory affects how well you retain and recall information during a task. Entering an ATM PIN seems trivial, but it depends on long-term memory retrieval under time pressure. Systems that demand users remember too many steps or codes invite errors.
• Mental models are your internal expectations about how a system should behave. When you swipe on a smartphone, you expect the screen to scroll in a particular direction. Interfaces that violate users' mental models feel confusing and slow people down.
• Information processing speed sets hard limits on reaction time in critical situations. Emergency braking systems in cars account for the roughly 1.5-second average human reaction time by adding automated responses.
• Spatial cognition supports navigation and manipulation of objects in space. 3D modeling software, GPS maps, and surgical robots all depend on the user's ability to reason about spatial relationships accurately.

Cognitive psychology in interface design

Good interface design isn't about aesthetics. It's about reducing the gap between what the user's brain expects and what the system actually does. Several core principles guide this:

• User-centered design builds interfaces around users' existing mental models so interactions feel intuitive. Touchscreen gestures like pinch-to-zoom succeeded because they mimic real-world actions people already understand.
• Information architecture organizes content to minimize cognitive load. Well-structured website menus group related items together, so you don't have to hold a complex mental map of the site just to find what you need.
• Feedback and affordances keep users informed about system status and signal what actions are possible. A progress bar tells you a file is uploading; a button that looks raised "affords" pressing. Without clear feedback, users feel lost.
• Error prevention and recovery anticipates common mistakes rather than just punishing them. Undo buttons, confirmation dialogs ("Are you sure you want to delete?"), and input constraints (blocking letters in a phone number field) all reduce the cost of human error.
• Accessibility ensures interfaces work for people with diverse cognitive abilities. Adjustable text sizes, simplified navigation modes, and screen readers aren't extras; they expand the range of users a system can serve.
• Usability testing uses methods like think-aloud protocols (where users narrate their thought process while completing tasks) and eye-tracking (which reveals where users actually look on a screen) to uncover problems that designers might never predict on their own.

Impact of workload on performance

Cognitive workload refers to the mental demand a task places on you. When workload exceeds your capacity, performance degrades in predictable ways: errors increase, reaction times slow, and decision quality drops.

• Cognitive overload is a major concern in demanding environments. Air traffic controllers, for instance, must track multiple aircraft simultaneously. As the number of planes increases, accuracy and response speed decline unless the system is designed to offload some of that burden.
• Stress narrows attention and shifts decision-making toward faster but less careful strategies. Emergency responders under acute stress may fixate on one piece of information and miss the bigger picture, a phenomenon called attentional tunneling.
• Fatigue, especially from circadian rhythm disruption during shift work, impairs nearly every cognitive function: attention, memory consolidation, and executive control all suffer. Night-shift medical errors are a well-documented example.
• High-stakes environments like operating rooms and nuclear power plants demand specialized strategies. These include standardized checklists, crew resource management (structured team communication), and forced rest periods.
• Workload management techniques help individuals and teams stay within their cognitive limits. Task prioritization, attention allocation strategies, and automation of routine subtasks all play a role.
• Assessment tools quantify cognitive strain so it can be monitored and managed. The NASA Task Load Index (NASA-TLX) is the most widely used; it measures subjective workload across six dimensions, including mental demand, effort, and frustration. Physiological measures like heart rate variability and pupil dilation provide complementary, objective data.