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Human error and games – Reducing, and taking advantage of, slips and lapses

To err is human & to game is often to err. This blog takes a look at two of the main types of human error, slips & lapses, & discusses how they may be relevant to game design. Both in terms of reducing & enhancing the likelihood of their occurrence

Playing games is often an exercise in error. We, as wonderful humans, make errors all the time, and when it comes to games we try to perform while accepting a certain level of error (i.e. I cleared that level, I got hit 20 times, but I didn’t die, so time to move on) or, if so inclined, work to minimise or eliminate error (i.e. perfect runs). Errors come in many shapes and forms but the ‘Skill-Rule-Knowledge’ framework of Rasmusssen and the writings of Reason gives us one way to look at them [1].

One aspect of this framework is ‘Skills’, skills being the term for the mostly automated way that we go about our lives and our play (sometimes also called ‘muscle memory’ or, more accurately, ‘procedural memory’). This is where you can launch a fireball in Street Fighter without thinking about how your fingers have to move and which button you have to press, or last hit in a MOBA without having to consciously work out the timing. Errors that occur at this level are the most common type of error, and therefore an understanding of when they are likely to happen could be useful when designing gameplay experiences (both to prevent these errors and to take advantage of them in terms of introducing challenge in a game).

Before going on, I want to make clear that this blog post isn’t just about removing error from games. There are many situations in games where players shouldn’t be breezing by error free. Games are often about challenge, and as such knowing about errors and how they occur is not just useful for user experience and usability in terms of reducing the likelihood of error, but also could be useful from a game design standpoint for increasing errors and therefore the challenge of a game. As such, in the sections below I will first outline the error type, and then for each error type give a few examples of how, perhaps, the likelihood of particular error type mentioned occurring could be reduced or encouraged.  

A technicality - Slips vs Lapses

A first distinction that can be made is to split these, automatic mostly unconscious, types of errors into Slips and Lapses. Simply put, slips are when a physical action goes directly wrong (i.e. you automatically press the “X” button without thinking when you meant to press the “O” button) and lapses are where a mental action goes wrong (i.e. you forget to go change equipment loadouts before starting your next game of CoD because you were shouting at your cat to stop attacking the screen). Ok, so that is the distinction. Fine, but what really matters is why and when either a slip or lapse occurs, so let’s get to that. Again, here there are two major groupings.

Errors of Inattention (or Omission) – “Sorry, I wasn’t paying attention”

Errors of inattention or omission are related to how much attentional capacity your player has (a limited resource) and what is going on at any particular time. So, basically, these are errors that occur because someone is overloaded or distracted. These errors can be further broken down into several types of errors of inattention:

A double capture slip – “Why I kept jumping up and down in front of vending machines in Bioshock”

A double capture slip is where you are distracted and/or overloaded, running on automatic, and the behaviour that you would usually do in a certain situation takes over rather than the behaviour you intended to do. So, for example if you are playing a MOBA or a RPG and you usually put a healing item in a certain equipment slot. Then pressing the button related to that slot in situations where you need healing will become relatively automatic. However, if you get into a situation where you happen to have another item in that slot and are panicked and/or distracted in the middle of a big fight (your attention is captured in other words) you may find yourself automatically hitting the button that is usually associated with the healing item, even if it is not there. This type of error is usually pretty immediately clear, although sometimes it does lead to an “I am hitting the stupid heal button! Why isn’t it working!?” type of confusion Another common situation is where you have played a lot of one type of game in a genre, for example a FPS that uses the “A” button for, say, jumping. Then you play another FPS that uses the “A” button for interacting with things in the world. What you will find is that without thinking about it that you will sometimes get in the frustrating situation of jumping when you don’t want to jump and interacting when you don’t want to interact.

  • Error reduction: Try to use design to setup environmental cues that make it very clear that a situation has changed from the norm. Be consistent. If a player has had to use a certain skill or button over and over and over in your game expect that they will have a tendency to automatically use this skill/button in appropriate situations (great, you want this generally), so think about it if you are going to change what that button/skill does or how the game environment interacts with it. This can be helped by keeping things standard (i.e. only healing items go in the healing slot) both within your game but also between similar games in the genre (e.g. right click to move, left click to select). Also if there are controls that are pretty standard for your type of game think about using them (or including them as an option) (i.e. the Halo control scheme or the CoD control scheme for FPS games on consoles) While you are at it, for accessibilities sake as well, consider letting the player customise their own controls.
  • Error encouragement: Establish habits. Get players to do an action over and over and over again. Or use habits that gamers may have picked up from other games. Then place them under load and change what that action does or the situation so that performing that action is no longer the correct thing to do. Basically, establish patterns of responding, then change that pattern (a classic Simon Says trick). Inverting the aim controls in a battle (such as the final boss in Dead Space) would be an example of encouraging this type of error in that you are effectively forcing the player to fight against their ingrained automatic tendencies while in a stressful situation (or, if they are lazy like me, pause the game, go into the controls and invert the controls so that they are “inverted” back to normal). 

Oh bumper jumper, I dare not try you as if I liked you, you would ruin me forever in other games

Oh bumper jumper, I dare not try you as if I liked you, you would ruin me forever in other games

An omission following interruption – “I’m sure I saved those changes…”

An omission following interruption is where you start to do one thing, stop and do something else, then pick up the first task again and skip a step (or a few steps) in the original task that you were doing. For example, you start modifying your skill tree in a game, get interrupted by a notification (or just suddenly remember) that you have unlocked a new weapon, go look at that new weapon or dismiss the notification, and then come back to the skill tree and forget to put points in what you originally intended to (or forget to save your changes). This type of error can actually take a while to detect. This is because one characteristic of an omission following interruption is that while you have skipped a step you actually think that you have done everything you need to do. So unless there is an immediate consequence for skipping the step it may take a while to discover your error (“what do you mean I didn’t save before closing the game?!”).

  • Error reduction: Try things like making sure important steps cannot be skipped, reducing unnecessary interruptions during important multistep tasks, having the software do the checking for the player (making sure important decisions are highlighted and confirmed. For example, use exit guards, e.g. You have not saved your changes, if you leave this screen they will be lost), and you could even reduce the number of multistep tasks (i.e. reduce multitasking). Generally speaking, add in immediate consequences or prompts for forgetting important actions. Making decisions forgiving will also help with this (and most of the other errors), for example allowing skill respecs, using good checkpoints, and/or allowing for manual saving.
  • Error encouragement: Try giving players lots of things to do at once. Especially if new tasks arrive in the middle of tasks that are currently going on. Don’t provide cues to help with memory or alert players to missed steps. 

Mr.Resetti is a personification (mole-ification?) of a save prompt and adds additional consequences if you forget to save your animal crossing game.

Mr.Resetti is a personification (mole-ification?) of a save prompt and adds additional consequences if you forget to save your animal crossing game. 

Delay reducing control – “Ahh, the Arathi highlands… why am I here?”

Delay reducing control is another familiar and frustrating error. It is where there is some time (and often space) between when you start the intent to do a task and when you actually perform the task and, because of this delay, things go wrong. An example of this would be being in your crafting location in a game, and you realise that you don’t have enough crafting material to make a certain item. So you travel to wherever it is you can get the material you need but when you get there for the life of you, you just can’t remember why you came in the first place. This is also sometimes known as the “What am I doing here?”, “What was I supposed to do here?” or even worse, the “I should be doing something but I can’t remember what?” effect. One theory for why this error occurs is that by changing environments you have removed the cue in the original environment that triggered you to want to do the action in the first place. So in the example above, you were in your crafting room looking at the recipe you were trying to use. But when you get out into the world, that cue is missing, and because you were kind of operating on autopilot, it can be hard to recall what it is that you wanted/intended to do. Another example would be finding an object in an adventure game that suggests you have to backtrack to a previously visited area, but you can’t exactly remember where that was, or when you get back there you forget why you came. 

  • Error reduction: Make cues portable e.g. through the use of quest logs, journals, prompts, map markers, and so on. Basically, use reminders and affordances in the world to support what the player wants to do. Also at an extreme level you could just avoid quests/tasks that require travel to different locations or that require time delay before the intent to perform the task can be turned into action.
  • Error encouragement: Spread tasks over multiple locations but limit the instructions about how to perform the task to specific circumstances or places (i.e. a bit of dialog or a note written on a wall). Make sure that time passes between when the intent to perform an action starts and when it needs to be completed, and make sure other events occur in-between those two points. Require backtracking to other locations, with very little (or no) cues to assist in remembering these locations. 

Errr, why did I come here again?

Errr, why did I come here again?

Perceptual confusion – “Oops! Missclick!”

Another common one, a perceptual confusion is the term for an error that occurs because two or more things appear similar and your brain fails at the pattern matching required to select the correct one. So, for example, accidently shooting at a teammate because you thought they were the enemy.

  • Error reduction: Use distinct shapes and silhouettes for other players, enemies, buttons, and important items and objects in the world. Clearly highlight important items/objects/people/places when they are to the current gameplay situation (and don’t highlight them when they are not).
  • Error encouragement: Make things look similar unless carefully examined. Then place the player under load or distract them somehow. For example looking for one specific crate in a warehouse of crates while at the same time fighting off bad guys, or pressing the right order of flashing, identical looking, buttons to enter a code within a certain time limit. 

  Is the difference between the Russian and the US assault class enough for fast decisions to be made? How about at a distance? Do you want the chance for confusion and friendly fire or not?

Is the difference between the Russian and the US assault class enough for fast decisions to be made? How about at a distance? Do you want the chance for confusion and friendly fire or not?

Interference errors – “Why are you in the Hinterlands? I said meet me at Aeris Landing not Aerie Peak”

Interference errors are often referred to as Freudian slips (which is where you say one thing but mean your mother). Basically it is like a perceptual confusion of your own thought processes, where because two or more things are linked cognitively (at a verbal level they may sound the same, but also thoughts can be linked simply by being related in terms of the task they apply to without needing to sound similar) they get blended or combined in your head. This can also occur as an intrusion of strongly cuing/attention grabbing objects in your environment, i.e. something that catches your eye or pops into your head that then mixes with your current thought processes. Note that while these are mental confusions, they can still lead to behavioural outcomes, like going to two very similar sounding locations in a fantasy setting or accidently buying one axe when you meant to by another axe when buying them in a RPG.

  • Error reduction: In a similar fashion to perceptual confusion make sure ideas and terms you use are distinct and avoid overloading the player (this can be especially important in fantasy or science fiction settings where players have to learn lots of new terminology). Also, avoid unnecessary multitasking and presenting unnecessary information in the middle of a task. Allow the use of chat macros to reduce the change that interference errors slip into commonly communicated commands (i.e. someone saying “go bot” when they meant to say “go mid” in a MOBA – because at the time they were saying it they were looking at mid or thinking of the fact they had to go mid).
  • Error encouragement: Use lots of similar looking or sounding names for different things in the game. Also, have the player make decisions about or remember terms/information that have similar names or are strongly related to each other in terms of form or function while they are under pressure. 

Errors of Overattention – “Stay on target, stay on target”

Errors of inattention are what usually come to mind when thinking about errors. They make sense. What may be less intuitive is that errors can also occur when you give too much attention to task. Think of when you have been playing a game and you are going along fine, making jumps and doing all the moves you should, but then you make an error and get back to the start of the level or sequence. Nuts, all that hard work for nothing. “Ok” you think “time to really concentrate and try again” except now you can’t do it. The jumps you were clearing with ease are now frustrations of the highest level. This is because, much like not having enough attention to go around, applying too much attention to performing a familiar task can be a bad thing (“Use the force Luke…”).

Basically, the advantage of automatic skilled behaviour means that we can perform complex tasks without having to try particularly hard. In fact, our daily lives, let alone playing games, would be impossible without our impressive ability to form and use automatic skills. However, when we do focus our efforts and really try and do something what we can end up doing are doing is engaging ‘higher’ level cognitive processes that do require considerably more effort and don’t handle interruptions and distractions as well as if we were just relying on our well learnt skills. Meaning that now you just don’t have the capacity to perform as well as you could. In addition, the pesky ‘higher’ level cognitive processes can also start getting in the way and bring with them their own biases and errors.

Another theory for why this occurs, is that when you concentrate on trying to avoid doing something (like missing a jump) you may, ironically, make it more probable (actually called ‘ironic processes’ by Wegner). The idea here is that by thinking hard about not doing something you may actually be activating the areas of your brain that are related to doing that thing, and then if you become overloaded the automatic action patterns related to the action that you want to avoid kind of “pop up” and grab control (like when someone tells you to not think of a white bear, don’t do it! Don’t think of a white bear!). These ‘ironic processes’ could be offered as an explanation for in an open world driving game like Saints Row when you are trying to avoid hitting other cars during a tense chase you find yourself hitting obstacles all over the place. Yet, later, when the mission calls for you to actually hit a certain vehicle or object you keep missing it, despite it being similar to those objects you were unable to avoid before. In this case, your overattention is, paradoxically, making what you want to do harder and what you don’t want to do easier.

  • Error reduction: Design for Flow. Aim for your players to be able to reach a state of effortless performance and then don’t get in the way. However, if the flow is interrupted and a cycle of failure begins then try providing a break or alternate activity for the player. Suggest (or even just introduce) a new pattern or objective for them to try for a bit. Then they can come back and stop over thinking the task they were having problems with. Perhaps you could also suggest a break or have a wise old kung fu master tell them to clear their minds. You could also offer to skip the section or lower the difficulty level, however, this may make things worse in some cases by focusing the player even more on their failures.
  • Error encouragement: Get in your players face with complex interacting systems that overlay and mix with relatively simple automatic skills. Get them to perform, multiple, incompatible tasks. Point out where they are going wrong with text or other information aimed at engaging their conscious processing and make them think about their actions explicitly. Let them know they have to try harder. 

  “You have missed that jump 20 times in a row. You clearly suck so would you like me to lower the difficulty setting?”

“You have missed that jump 20 times in a row. You clearly suck so would you like me to lower the difficulty setting?”


Humans make errors. Games would likely be pretty boring if we didn’t. When looking at these errors, at the ‘skill’ level, there are two major types. Ones that occur due to too few attentional resources and ones that occur because too much attention is being given to a relatively simple, usually pretty automatic, task. When dealing with these errors you can try to reduce their occurrence where it will distract from your game (i.e. in the basic use of the interface and so forth) but at the same time you can take advantage of them to add challenge and difficulty to your games.

Ultimately much of what of I have outlined above could be called old hat usability or user experience guidelines. However, I don’t think it is a bad to be reminded of usability and user experience concepts, like those mentioned above (although this is not in any way a comprehensive list of suggestions and solutions – got more? Please do share them) that can help, both to make your game harder (and hopefully therefore more challenging and enjoyable) and/or to make the experience smoother (and hopefully also more enjoyable).


[1] - If you are interested I wrote an introduction, in a much too long fashion I have been told, about the Skill, Rule, Knowledge framework and games back in 2010. 


Human Error by James Reason

Ironic Processes of Mental Control by Daniel M. Wegner

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