What are Human Factors?

Since we're going to spend some time talking about human factors on this site, it's probably a good thing for us to have a common understanding of what this term means, particularly in the context of aviation.

Human Factors in aviation

You may have heard of this term as it's used more generally around incident investigation reports. In trying to piece together the situations that arise behind an incident, investigators frequently refer to the human factors of the cockpit.

This is a catch-all term covering how pilots interact with the many systems within and outside of the cockpit--what they can see, hear and feel (typically in a tactile sense) around them.

Oftentimes, they even try to reconstruct what the pilots are thinking and feeling in the minutes leading up to an incident: other than what they perceived, what did they think was going on?

The study of human factors

Ergonomics argues, that in order to optimise the performance of a system, we should also consider the productivity, comfort and safety--the well-being--of the human that operates within it.

Also known as Ergonomics, the interdisciplinary field of Human Factors asks that we do not design systems in isolation, but to consider their users' psychological, physical and indeed emotional state when they are interacting with the system.

A goal of the field is to ensure that "human error" is not the go-to explanation for a system failure, but that errors made by humans are fully accounted for and can actually be a useful starting point in retrospective analyses. It recognises humans as imperfect beings, and tries to design resilience into our systems to guard against when people inevitably make mistakes.

More generally, it tries to understand the full context in which a person may use a system, and analyses how the system (which can be physical, digital or even social), its users, and the environment all interact with each other.

Ergonomics argues, that in order to optimise the performance of a system, we should also consider the productivity, comfort and safety--the well-being--of the human that operates within it. We're essentially choosing to focus on the factors of a system that relate to humans.

Principles of Design

So you might be wondering, aren't airline seats already made for humans? What other factors can there be in the passenger experience?

Let's start with what we're not covering: food, service, crew and ground staff--traditionally referred to as the Soft Product. It's not that these are not important to the comfort and well-being of the flyer, but the way to assess and critique these requires a different framework of analysis rather than the one we will take in this blog.

Following the bible of User Experience, Design of Everyday Things, we'll look at the physical and digital surfaces in aviation by following these 6 principles of interaction design (by author Don Norman, and paraphrased by me):

1. Affordances: Does the system allow you to perform your desired actions?
2. Feedback: Is there full and continuous information about the result of your actions, and the current state of the system. After you've performed an action, is it easy determine the new state of the system?
3. Signifiers: Does the system communicate in a perceptible manner (that is, visually, aurally or otherwise), what you're allowed or not allowed to do, its current state and any feedback to your actions?
4. Constraints: Are there physical, logical, semantic and cultural constraints that guide your actions and ease your interpretation of the state of the system and feedback?
5. Conceptual Model: Does the system's design allow you to create a intuition for how it functions? Does this mental model allow you to understand it and possess a sense of control?
6. Mappings: Is there an obvious relationship between the controls of the system and actions that thy perform, and are these enhanced through spatial layout and temporal contiguity?

The Flyer's Factors

These 6 principles may feel like a lot, but they can be grouped into 3 main questions that you probably already ask yourself every time you fly:

1. What's in front of me?
2. What can I do?
3. What happened after?

Q1: What's in front of me?

Principles: Discoverability, Signifiers, Constraints, Conceptual Model

This is something we do every time we have a new experience, be it using the website of an airline we've never flown before, or trying out a new seat design.

Think about the last time you landed in a airport for the very first time. Once you leave the jet bridge, you find yourself in a terminal full of people moving in all directions. Where are the toilets? Where is my connecting gate? How do I go to immigration and baggage?

The layout of both an airport and a website help you quickly form a conceptual model of where you are, what's around you and how to get you to your destination.

Terminal gate areas tend to be long corridors to reduce the number of directions you can walk in, much like how booking forms always have two columns: departure on the left and arrival on the right (or sometimes in 2 rows to accommodate for right-to-left languages).

These constraints reduce the complexity of the world around you as well as the mental model you need to construct. Imagine if every corridor intersection branches out to 5 more corridors!

Together with signifiers such as icons, colour, and signage, they help you quickly establish a conceptual model with you at the centre, and the new place extending around you.

Sometimes you can overfit your experience to your conceptual model--if you're used to entering the long queue for immigration, because your conceptual model includes "queue for immigration" as a necessary step, you might miss out the fact that the airport you're at may no longer require you to join a queue or speak to an immigration officer.

That's why when changes are made to the procedure of arrival at an airport, there's often a lot of obvious, glaring signifiers to inform and remind you, and plenty of constraints preventing you from going down the wrong path.

Q2: What can I do?

Principles: Discoverability, Affordances, Signifiers, Constraints, Conceptual Model, Mappings

Constraints also help us understand what actions are permissible within the bounds of the system: walls, red no-go signs and greyed out form buttons tell you where you can't go and what you can't do. If the airport has a pair of walking travelators, can you tell from a distance which one you're allowed to walk onto before getting too close?

Does the booking website prevent you from choosing a return date that's before your departure date? What about buying a ticket between two airports that your airline doesn't fly between? You can't be expected to know which airports your airline is flying to this season, so preventing you from selecting certain airport pairs exists as a constraint that further helps you understand what actions you can perform.

Signifiers and affordances help you constantly refine your conceptual model of how the system works. The first time you're prevented from doing something, you might think it's a bug, or a one-off error. But if you keep encountering the same situation, you will eventually update your conceptual model of how the system works.

Lately, boarding announcements have started to request that if you drop your phone somewhere you can't reach, to call for a flight attendant rather than trying to retrieve it yourself. This is so that you don't accidentally adjust your seat in a manner that crushes your phone, which might cause a battery fire.

Why might this happen? There are many storage areas around your airplane seat, regardless of what class of service you're in, and no one of them is ever device-sized, so we put our devices where looks most like a pocket. Have you tried to put your phone into one of these only to have it fall out the bottom?

It looks like a pocket; if it has literature in it, it definitely affords storing something thin in it. But it's fairly tall, and has some depth to it, so when you drop your phone into the top, it might bounce around and fall out the bottom.

Or it might get safely caught by the lip, but how do you get it out? The big horizontal bar blocks your grip so you might have to push it from the bottom with one hand, and fish it out using your other hand.

Your conceptual model of this part of the seat being a pocket, unfortunately has to be revised through a negative experience.

I recently flew Premium Economy on Cathay Pacific and tried to recline my seat when the double ding chimed to indicate that we had climbed past 10,000 ft. I pressed the recline button, but my seat didn't recline. I tried pressing harder, since sometimes buttons get stuck (referring to my conceptual model of how buttons work, based on years of experience pressing buttons!)

The buttons you see below were in the hand rest, where recline buttons tend to be. So I intuited each button's function based on its relative placement, and relied solely on my sense of touch instead of visually inspecting each button for any clear signifiers.

Given that my seat was facing the same direction as the seat outline on these buttons, why did you think my seat wasn't reclining? Indeed, I was pressing the wrong button.

I had pressed the back-most button (left-most in the photo) thinking it was for the seat back since my mental model of the parts of the seat mapped over to these three buttons: seat back, leg rest, foot rest.

In my mind, the part of the seat furthest back should have been controlled by the button furthest back in the row. But instead the buttons in this seat were installed wrongly, and the seat back button was actually the front-most button.

I looked over at the buttons on the seat handle next to mine, and sure enough, that one had the seat back recline button furthest back. Thankfully, the symbols on the button correctly represented the part of the seat that it controlled, so I pressed the front-most button (right-most in the photo), and managed to recline my seat.

The buttons correctly mapped over to their functionality, aided by meaningful signifiers. However, the spatial mapping that helped to distinguish one button from the next was incorrect due to the button being installed in the wrong position.

Q3: What happened after?

Principles: Discoverability, Feedback, Signifiers, Conceptual Model

Feed

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Flying in general can be a fairly stressful activity. We're disrupting our daily lives to go into an airport full of people, get through security theatre designed to make you feel criminal, and then jump into a flying metal tube and hope that you land safely on the other side.

That's why the feeling of agency is so important throughout the whole process. Once you factor in the time and distance requirements, you often find that you don't have much choice as to how you get to your destination.

That's why the feedback that you get from every interaction with an airline is so important--it gives you a sense of control in what is otherwise a highly structured activity that's largely out of your hands.

If you've ever tried using Google Flights to buy a flight, you know how frustrating it can be that after you've calculated all the options and tradeoffs and arrived at a specific flight, only to click the "Buy" button and be told that the price your chosen flight has "expired".

At least you get a screen preventing you from buying a ticket which doesn't exist, but at no point during the selection process were you informed that the price you see is actually invalid.

Because airline tickets are continuously dynamically priced, we'll never truly know why a price no longer exists, even if the seat on that specific flight is still available for purchase. We know that in general the earlier you buy a ticket, the cheaper it is, and some sources even recommend buying flights on a Sunday, where ticket prices tend to be lower. But with so few signifiers, our conceptual models of how airline tickets are sold remain fuzzy at best.

Buying a ticket is merely one of the many action-feedback loops we engage in with airlines. Once you've submitted your credit card details online, it can sometimes take up to 24 hours for an airline to issue your ticket,

Discovery: the overarching principle

As you'll have realised by now, the main thing that we do when interacting with any system, is whether it's discoverable. We're constantly trying to determine the current state of any system, and what actions are possible so that we may achieve our goals. At any time, when we perform an action, we're asking ourselves: am I able to determine what happened? Or if something unexpected happens, to determine the source of the error?

Discovery is so key to any experience, because many of the things we interface with are black boxes: we simply don't have enough information about how it functions and how we can affect change within it. Our conceptual models are just that -- models that oversimplify, but that are good enough to let us perform an action and get on our way.

Just as well, this key principle of discovery is so apt for the frequent flyer. What's more exciting than flying around the world to discover a new cuisine, language and culture?

Further Reading

Here are some of my favourite sources to learn about the psychology of how we interact with systems, both digital and physical.

Some links are affiliate links, so if you buy a book using the link, you'll be supporting me write this blog!

• Growth Design - Usability and user experience case studies of popular apps, including a great list of cognitive biases and psychological concepts to help understand why things are designed the way they are!
• Design of Everyday Things - The OG book by Don Norman on designing interfaces that spurred the industry of UX.
• Abstract: The Art of Design - A wonderful Netflix series discovering different types of design we encounter in our daily lives
• Thinking Fast and Slow - A deep dive by Nobel Prize author Professor Daniel Kahneman into the cognitive-psychological underpinnings of how our minds work--and sometimes don't work.
• Flow: The Psychology of Happiness - The seminal work by Professor Mikhail Csikszentmihalyi on how time flows by when you're fully immersed by a task