Have you ever had someone give you a list of words written in different colored ink and asked you to ignore the word as written and instead say the color of the ink that the word is written in? It isn’t too difficult when you see random words, but it becomes much different when you see the names of colors written in different colors, such as green written in red ink or the other way around. The difficulty with reading the color and not the word in those situations stems from poor stimulus response compatibility. The brain receives a signal in the writing of the word, and has to overcome that signal to say a different color.
Richard Thaler and Cass Sunstein use this as an example in their book Nudge. They also demonstrate stimulus response compatibility using an example of a door with round wooden handles in a classroom that Thaler once taught in. The handles sent a signal to student and anyone else exiting the room that indicated they were intended to be pulled in order for the door to be opened. However, the doors needed to be pushed open. Describing the confusing doors and the poor stimulus response compatibility, the authors write, “you want the signal you receive (the stimulus) to be consistent with the desired action. When there are inconsistencies, performance suffers and people blunder.”
Stimulus response compatibility is crucial in terms of website design, road construction, slide presentations, video games, and any other setting where cues are used to indicate a desired behavior. People need to understand where to click to add an item to a shopping cart, how to scroll through a website, and how to close out of any pop-ups. Drivers need explicit cues for when it is safe to drive through an intersection, and inexplicit cues can help drivers understand when they need to slow down. Visual, audio, and other stimuli can drive predictable responses in people, and they can be used as nudges to help encourage or discourage certain behaviors. Understanding the stimulus you are providing and whether it is compatible with the behaviors you want people to exhibit is crucial.
Most of us probably want to develop good stimulus response compatibility, but we should also note that it can be used to frustrate people and prevent certain behaviors or goal attainment. If you have ever tried to unsubscribe from an annoying email list or newsletter, you may have experienced the challenges of intentionally poor stimulus response compatibility. Instead of having a clear link at the end of the email to unsubscribe, the link might be a dull gray color. The link might take you to a page with unclear directions on what buttons you needed to select to unsubscribe from all future emails. You may have seen a green button prominently placed that re-subscribed you instead of unsubscribed you from the emails, thwarting your plan to declutter your inbox.
It isn’t quite the case that these nudges are methods of mind control, but they do influence our behavior and can shape how we behave, what we learn, and real outcomes in our lives. If we are choice architects, we should recognize what behaviors we are trying to encourage, and think about the subtle cues and stimuli we can present to encourage people to make decisions that are in the best interest of the individual making the choice – as measured and determined by them, not us. Nudges are powerful, especially when a good stimulus response compatibility is in place. Importantly, nudges are not the kinds of roadblocks and obstacles that I discussed in the example of trying to unsubscribe from an email list.