The design principle/heuristic I have chosen is error prevention, more specifically, the idea of giving the user confirmation options to stop them from executing actions that they don’t mean to execute. This heuristic comes from the Nielsen article, which states that, while detailed error messages are useful, what is more useful is “either eliminating error-prone conditions or checking for them and presenting users with a confirmation option before they commit to the action”. This heuristic is important because it ensures that users can stop errors before committing them, which reduces the need for detailed error messages, because the user can stop errors in the first place by confirming their actions.
Venmo provides a good example of inserting confirmation messages at key points in the user experience. For example, after a user has created a new transaction, inserted a transacting party, amount of money, and a subject line for the transaction, they press Request or Pay. After pressing either option, the button changes into “Request $X.XX from Mary” or “Pay Mary $X.XX”. This provides a comprehensive confirmation, in that the user can see what transaction they are making (request or pay), who they are transacting with, and how much money is being transferred. Thus, this confirmation message allows the user to stop the transaction if it is incorrect, instead of having to complete the transaction and then find a way to reverse it.

(Create transaction, then choose pay or request)         (Upon selection, app makes you                                                                                                                    confirm the nature of the transaction,                                                                                                                       the amount,  and the recipient)

Apple’s mail app violates the principle of error prevention through the use of confirmation messages. When in any particular mailbox, selecting an email gives a toolbar at the bottom with 5 different icons, and the one in the center (right above the home screen button) is a storage box icon. If you press this button, it appears as though your email immediately disappears. On closer inspection, it becomes clear that the email was simply archived and moved to the All Mail folder, from which it can be moved back to its original inbox. However, this storage box button has no confirmation message, so if you press it by accident (as is easy to do, since it’s right above the home screen button) your email appears to simply disappear. There is an easy fix to this problem, and all it includes is adding an extra pop-up that asks whether you want to archive the email in “All Mail”. Depending on what the user actually wants to do, they can confirm or deny, thereby reducing confusion and making the experience of sorting mail easier. Furthermore, if the user actually wants a one-click archive option, there should be functionality that allows the user to enable that, instead of having the one-click option as a default, since this option can be confusing to users and can lead to unnecessary difficulty in trying to find emails that appear to have just disappeared.     

For example, I open my Gmail inbox  and see this email. I accidentally press the archive button in the middle (labeled with red arrow) and the email “disappears”.

I then have to leave my inbox, go to mailboxes, and select my Gmail account.

I then have to find the All Mail folder in my Gmail account.

From there, I choose the All Mail folder and find my email (the first email in the folder).

I have to go through this entire proceeding because there is no confirmation message for the archive feature.

This is a pretty easy thing to change. We can add a confirmation message so that, when the archive button is pressed, the user has to confirm whether they want to archive the email. There can also be a “Do not show this message again” option for those who want one-click archiving. After one presses the archive button, the new version may look like this. The new version gives the user an opportunity to confirm the action, then also tells the user what the action does and how to reverse it. The pop-up also gives the user the chance to streamline their workflow by supporting one-click archiving, but does not assume that the user wants one-click archiving. With this new feature, users will not experience the annoyance of accidentally archiving an email and having it “disappear”.