Doing the right thing should be easy.
Da Vinci’s Vitruvian Man
Human engineering isn’t what you might think. It’s not a eugenic nightmare of bioengineering and gene selection. Thank goodness, it’s much more benign. Instead, human engineering is a multi-disciplinary field that brings together psychologists, engineers, cognitive scientists, organizational behavioral specialists, and designers. Their goal is to make it easy for people to do the right thing. [Redacted: High brow “A Clockwork Orange” joke] Sometimes referred to as interaction design or cognitive ergonomics, the aim of human engineering is to improve human performance by looking at systems.
Simply put, human engineering tries to make it easier to do the right thing and harder to do the wrong thing for any task or activity. This aim is achieved through the design (and alteration of existing designs) of the technology, systems, and environments that individuals interact with. Immediately we see the application of human engineering into the paradigm of system dynamics and human error.
There are many principles of human engineering, but one of the most important is the importance of designing the interactions of humans and objects to align function with action. To demonstrate, consider the very common scenario of turning on a burner on the kitchen stove.
The Mysterious Case of the Wrong Burner
Has it ever happened that you’ve gone to turn on the stove and lit the wrong burner? It’s not just you. It’s a very common problem and one of the most studied topics in the field of human engineering. Stoves are not advanced technology and lighting the stove only requires one turn of the knob. So how come we’re so prone to these simple mistakes?
The answer has to do with the way the alignment of form and function. Stovetops are tremendously bad at this alignment. Consider two popular configurations of commercial stoves:
Source: Design of Everyday Things
In typical stove designs (let’s call them Configuration A and Configuration B), we see that the burners are aligned as a 2×2 rectangle, whereas the knobs are aligned linearly along the front. The knobs and the burners are configured differently. To use a technical term, we could say that these configurations have poor spatial compatibility.
Configuration B is slightly better than Configuration A, because there is a natural grouping between the two burners and knobs on the left and the two burners and knobs on the right. Nevertheless, in this configuration errors will be common and proper use will rely on reading the labels on the knobs or trial and error. In short, it takes some level of cognitive effort, beyond intuition to ensure consistent proper use of the stove.
The Better Way
Now consider two slightly different configurations. In Configuration C the burners are still arranged in a 2×2 rectangle, but now, the knobs are also arranged in a similar way. There is a natural alignment between the controls and the device. No labels are needed.
Source: Design of Everyday Things
Configuration D provides another natural and intuitive layout, but this time maintains the linear arrangement of the knobs. Simply by bringing the two back burners closer together to align with the knobs, the stovetop has gone from an inscrutable, error-prone appliance to something that is intuitive and easy to use.
Without objection, we can see why the stovetop configurations in Configuration C and Configuration D are better. Not only will these configurations produce fewer errors and lead to more consistent and effective operation of the stove but they also rely on intuition and require less cognitive processing to achieve the greater result! A win-win!
Oh by the way, how much did the change cost? We used the same space, the same controls, and the same materials. We can decrease errors, build resiliency, and decrease the cognitive load without sizable investments! Win-Win-Win!
The Principle of Spatial Compatibility
What we’ve just witnessed is the principle of spatial compatibility in action. This principle states that controls should be arranged to correspond naturally with the devices they control. When there’s a clear, intuitive mapping between control and function, people simply know what to do. No thinking required. No labels needed. No errors made.
This might seem obvious when pointed out, but look around your environment. How many poorly designed interfaces do you interact with daily? How many times do you have to stop and think about which button does what? How often do you make “simple mistakes” that are actually design failures?
The stove example illustrates a profound truth: most of what we attribute to human error is actually design error. We blame ourselves for our mistakes when we should be blaming the systems we’re forced to work within.
When Design Betrays You
Stovetops are not the only place where we encounter human engineering in our daily lives. Even something as simple as a door can pose significant challenges to human-technology interaction (Yes, a door is technology). We’ve all been in that embarrassing situation where we push a door that should’ve been pulled and vice versa. But have you ever stopped to ask why you made an error? Take solace in knowing that it was the door’s fault and not your own.
These doors did you wrong. They betrayed you. They gave a signal that was incorrect, and your only fault was that you trusted them. Who knew that doors could be so deceitful? Take heart, this is a very common problem. One person who this has happened to a lot is Don Norman. Don knows a lot about these sorts of doors. Don has studied these doors so much that these species of doors are actually called “Norman Doors.”
In his book “The Design of Everyday Things” he explains:
“How can such a simple thing as a door be so confusing? A door would seem to be about as simple a device as possible. There is not much you can do to a door: you can open it or shut it…The design of the door should indicate how to work it without the needs of signs or trial and error.”
The Principle of Discoverability
The chief way these doors betray the user is by abandoning another fundamental and important design principle, the principle of discoverability. The principle of discoverability simply states that any designed object should make it clear to the user how to correctly use that object. In the case of the Norman door, not only did the door make it unclear, but it probably sent the exact opposite signal than what was required.
Consider a door with a horizontal push bar on it. That bar screams “PUSH ME!” to anyone who sees it. It’s a clear affordance — a visual cue about how the object should be used. Now imagine that same door with a “PULL” sign on it. The sign contradicts everything the door is telling you with its design. The horizontal bar is still there, still suggesting you should push, but now you’re supposed to ignore that signal and pull instead.
A Norman Door. Source: 99percentinvisible.org
This is fundamentally bad design. A well-designed pull door should have a vertical handle that you can grip. A well-designed push door should have a flat plate or push bar. The design itself should communicate the proper use without requiring any labels or explanations.
Why This Matters More Than You Think
The Norman door is an important example of human engineering in daily life because it showcases how the alignment of human action and the environment impacts our propensity to make mistakes. If something as simple, ordinary, and untechnical as a door can impact the decisions, efficiency, and productivity of individuals than how much more will this be true for complex systems.
Indeed, the inefficiencies of these everyday objects may seem trivial and insignificant but the underlying principles they demonstrate are anything but, especially when applied to industry. What these vignettes demonstrate is important and powerful. Using the same space and the same equipment for the stove, we nearly eliminated the possibility for error. No rework, no guess and check, no errors, no need for labels, less thinking, no need to stop and think about the result of our actions and all for no money.
Human engineering is potent and powerful.
The Core Principles of Human Engineering
While there are many principles of human engineering, several stand out as particularly important for designing better systems:
1. Spatial Compatibility: Controls should be arranged to naturally correspond with the things they control. The layout should be intuitive and obvious.
2. Discoverability: The design should clearly communicate how something is meant to be used. Users shouldn’t have to guess or rely on labels and instructions.
3. Feedback: The system should provide clear, immediate feedback about what’s happening. When you press a button, something should happen that confirms your action was received.
4. Constraints: Good design constrains behavior in ways that prevent errors. If something can only be done one way, and that way is the correct way, errors become impossible.
5. Mapping: There should be a clear relationship between controls and their effects. Natural mappings leverage existing knowledge and expectations. (I even created a fun Tetris game you can to play to demonstrate this principle)
6. Affordances: The design should suggest its own use. A handle affords pulling. A button affords pressing. A flat surface affords pushing.
The Human-Centered Design Philosophy
At its core, human engineering embodies a fundamental philosophy: when a person makes an error while using a system, it’s the system that failed, not the person. This perspective shift is revolutionary. Instead of training people harder, writing more procedures, or adding more warnings, we redesign the system so that errors become difficult or impossible to make.
This doesn’t mean humans are absolved of all responsibility. It means we recognize the reality of human limitations and capabilities, and we design accordingly. We accept that people will be distracted, tired, stressed, and forgetful. We acknowledge that people will sometimes be in a hurry, sometimes be interrupted, sometimes misremember.
Rather than fighting against human nature, human engineering works with it. Rather than demanding superhuman perfection, it creates systems where ordinary human performance is sufficient for excellent results.
The Cognitive Load Consideration
One of the most important benefits of good human engineering is the reduction of cognitive load. Every poorly designed interface, every ambiguous control, every unclear instruction adds to the mental burden people must carry. When you have to stop and think about which burner is which, or whether to push or pull a door, you’re using cognitive resources that could be applied elsewhere.
Good design frees up mental capacity. It allows you to focus on what matters rather than wrestling with interfaces. It reduces decision fatigue. It makes the right choice the obvious choice, the easy choice, the path of least resistance.
Think about how exhausting it is to navigate a poorly designed website, a confusing form, or a cluttered workspace. Now think about how effortless it is to use a well-designed tool. That difference, that feeling of friction versus flow, is human engineering in action.
Application Beyond Physical Objects
While we’ve focused on physical examples like stoves and doors, human engineering principles apply to every system you interact with:
Digital interfaces: Are your most-used apps and tools intuitive, or do they require constant mental translation?Work processes: Do your workflows naturally guide you toward the right actions, or do they create opportunities for confusion?Personal routines: Are your habits supported by environmental design, or do they require constant willpower to maintain?Communication systems: Do your methods of staying informed and responsive flow naturally, or do they create constant friction?A pime example of good work processes, ATMs require you to take your card before your cash, making it unlikely you error (forget your card) Source: bankrate.com/
In each of these domains, the principles remain the same. Make the right thing easy. Make the wrong thing hard. Provide clear feedback. Create natural mappings. Reduce cognitive load.
The Power of Environmental Design
Human engineering reminds us that we don’t need to become better people to perform better. We need to create better systems. We don’t need more discipline, more willpower, more training. We need environments that support us rather than fight us.
This is liberating. It means improvement doesn’t require becoming someone you’re not. It requires thoughtfully designing the systems and environments you operate within. It means recognizing that when you consistently make the same “mistake,” it’s probably not your fault — it’s a design failure waiting to be fixed.
The question isn’t “How can I be more careful?” The question is “How can I redesign this system so being careful isn’t necessary?”
That’s the promise and power of human engineering.
Human engineering was originally published in UX Collective on Medium, where people are continuing the conversation by highlighting and responding to this story.