One of the elevators in my building at work has a faulty button so whenever we swipe our security passes and push "8" the light goes on but there is no "bing". Push the button for any other floor and the "bing" reinforces that the magic elevator has recognised our request. If you want any proof that multi-sensory cues are important, just observe the body language of people who have not their button push confirmed - does any of the following sound familiar? Re-pressing the button. Repeated glances at the button. Nervous toe tapping as the targeted floor approaches. Heightened anxiety. Sounds ridiculous doesn't it? After all, the worst that can happen is you go to another floor and have to try again. And it is ridiculous - it is irrational. The innocuous absence of a "bing" can change your experience of an elevator trip.
In his book Brand Sense, Sensory Secrets Behind The Stuff We Buy, Martin Lindstrom talks about the importance of such sounds as the ding heralding the arrival of an email in your inbox and the sound of a car door closing. If you have a Mac computer you will no doubt be familiar with the unique...how do I describe this...vrrrr pop! that accompanies actions to close Apps. The iPod click wheel, the Nokia ringtone (which was, whilst recognisable, more a negative than positive for the Brand because it was connected to work...), tell us that sounds are vital to cue and/or reinforce behaviour.
Back to the lift in my building. Three of 5 senses are generally employed in the button scenario. Touch - pushing the button; Sight - a light to indicate the button has been activated; and Sound - the 'bing" to reinforce the button's action. Thankfully for now, Touch and Smell have been left out of lift button pushing (but not always out of the experience of lift travel unfortunately). As soon as the Sight or Sound cues are absent, the system breaks down and we all get a little uncomfortable.
So what is the lesson from the elevator? People subconsciously seek multi-sensory reinforcement of their behaviour and when one of the expected cues is absent, performance is sub-optimal. Think about your product or your marketing message - what cues are you setting up for your customers and are they reinforcing the desired (purchase) behaviour?