You know how sometimes, say you’re in the middle of doing something on your phone, and then suddenly it goes off on one, like it’s got a mind of its own, and does something you didn’t ask it to do?

Well, the reason might just have been because you made a rule based mistake.

A postnote publication (2001) from the UK Parliamentary Office of Science and Technology on Managing Human Error (PDF) was issued in the aftermath of the Cullen Report for the Ladbroke Grove rail crash.

The article describes issues around human attention characteristics:

Attention on a task can only be sustained for a fairly short period of time, depending on the specifications of the task.

One of the things that affects attention is habit formation:

Habit forming – if a task is repeated often enough, we become able to do it without conscious supervision, although this ‘automatisation’ of regular and repetitive behaviour can force us into mistakes.

The paper then quotes a great example:

The Automatic Warning System installed on all passenger trains in the UK is an example of a system that was not designed with limitations of human attention in mind. It is a device fitted in the train cab, based on the now obsolete mechanical system of signalling that used to signal either STOP or PROCEED. It sounds a bell when a clear (green) signal is passed and a buzzer when caution or danger is signalled. If the buzzer is not acknowledged by the press of a button, then the train begins to stop automatically.

In commuter traffic, most signals will be at the ‘caution’ aspect, and given the frequency of signals (spaced 1km apart), most drivers 
will face two signals per minute. Given the tendency for the attentional system to automate highly repetitive behaviour, many drivers lose focus on the reasons for carrying out this repetitive task, and act in reflex whenever the buzzer sounds. The end result is that drivers often hear the buzzer and press the button reflexively without actively thinking about train speed and location.
Source: Davies, D. (2000): Automatic Train Protection for the Railway Network in Britain [PDF] – A study. RA Eng., London

So – we are predisposed to automatically delegate repetitive actions to our subconscious whilst our ‘conscious brain’ deals with concentrating on other things that are going on around us.

How does this relate to the opening line above?

Well, did your phone really do something you didn’t ask it to do – or in fact did you make a mistake and select the wrong thing, believing it to be the right thing, because you were processing the action subconsciously – without time for the conscious part of your brain to recognise the current scenario did not confirm to the rules you believed were being adhered to and followed?

Here’s an example of how it can happen:

Android has a system of application updates. You can set the apps to update automatically, but when an app needs to ask permission to access more parts of the phone than a previous version, the app gets queued in the Play Stores list of apps requiring a manual update (at which point permission will be sought).

When you have a number of apps to update and you don’t want to ‘Update All‘, you have to go through a repetitive process of choosing an app in the list, waiting for the app page to appear and then clicking the Update button.

Flickr App Update on Android

By the time you’ve done a few of these, you start to form a repetitive sequence of actions – select app, press update, accept permisions, go back, select app, press update…etc

You start to offload the process to your subconscious.

So when you get this sequence of screens:

EventBrite App Update on Android

Path App Update on Android

Hangouts App Update on Android


Whoa! What’s going on, this app just opened without being asked!

Well, check the position of the update button in each screen. It’s in the same position on every screen (above the Uninstall button) – except the last one, where there is no uninstall option and the Open button has shunted the Update button down.

Because you’re in this subconscious repetitive action, you’re not even reading the words on the buttons any more. You know where the button is that you need to click. You know there’s two buttons and it’s the top one you need. There’s not enough of a different scenario for the subconscious to trigger an alert and raise the task up to the conscious processing.

The application opens – and only then do you take note of this unexpected event for what you believe to be inexplicable reasons. In all likelihood, if someone asked what you did you’ll say ‘I just pressed the update button and it just opened up instead of doing what I asked!’, probably followed by  ‘Stupid phone!’

And that’s how it happens. We see this very often on confirmation dialogs and other scenarios where we just don’t read what we see, we just subconsciously assume away.

When designing small interactions, have a thought for whether they are prone to repetition. If so, think about what alternate designs might prevent rule based mistakes, because it might not be just an app opening up – it might be a whole lot more serious than that!