The envelope problem

Or the importance of affordance in designing for mental models

A large corporation had a problem with it’s running costs. Much like most organisations they looked at where they may have been spending money unnecessarily and tried to find ways to become more efficient. In amongst their findings was an unexpected amount of money being spent on envelopes. When they looked more carefully they saw the problem.

Various teams around this corporation used envelopes to send internal mail between offices. Each of the internal mail envelopes had a flap with a strong adhesive tab to seal contents inside. For years recipients of internal mail envelopes ripped the adhesive flaps open rendering the envelope useless.

Despite the corporation’s desire to cut costs and use less paper the design of the envelopes meant they were ‘single use’ items and hundreds of thousands of pounds were spent each year on replenishing stocks.

The ops team saw the inefficiency and attempted to adjust the envelope design. The new solution now employed a velcro tab allowing easy sealing, opening and resealing. Although the new resealable envelopes were more expensive they are reusable and fewer would be needed. Seemingly the problem was solved.

However a review six months later showed that stationery spend had tripled. More investigation lead to this…

The resealable velcro envelopes looked identical to the sticky single use envelopes (except for a small text label). The mental model had been created for employees to instinctively rip the flap open.


The point of this story is to illustrate the problems that can arise when design and delivery (developers, engineers, manufacturers) don’t share a common outcome, but more importantly the problems shown here can be transposed to the process of designing for mental models.

If data or research has identified an issue with your design, the temptation is to simply adjust the place where the error is occurring (often the UI). Due to cost or time restraints this can be seen as the desirable route. Sometimes the designer will avoid an overt redesign for fear of disrupting the experience or contravening the style guide, however this can be problematic as a behaviours have been learned and expectations have been set.

The appropriate level of affordance cannot be overlooked or underestimated when adjusting existing interactions. In fact when a design moves from initial launch in to optimisation all designers should be hyper aware of how much their users have learned or come to rely on the expected responses. Where possible changes should be made clear and distinct.

There is also the concept of desire paths at play here. Before a design can be implented to ‘fix’ a problem, the designer must consider if this is in fact a problem or if this is a demonstration of what the end users want to do. There is a real possibility that the experience should be redesigned to accommodate the desire. Perhaps we desire a satisfying ripping sound on our envelopes.


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