In my last Four for Friday post, I included a link to some ridiculous products that appeared in the SkyMall retail catalog, which included a “covert” cat box/planter, a bizarre multi-function folding cane, and an unwieldy and impractical-looking “back massager.” I can only imagine what the shipping costs must be for some of these inane items.

However, the more I thought about these items, the clearer it became to me that the problem with many of the items was simply that they just try to do too many things, running head-long into the law of diminishing returns.

This is a basic concept of economics, summed up by the Columbia Encyclopedia as follows:

[The law of diminishing returns is a] law stating that if one factor of production is increased while the others remain constant, the overall returns will relatively decrease after a certain point. [...] The principle, first thought to apply only to agriculture, was later accepted as an economic law underlying all productive enterprise. The point at which the law begins to operate is difficult to ascertain, as it varies with improved production technique and other factors. Anticipated by Anne Robert Jacques Turgot and implied by Thomas Malthus in his Essay on the Principle of Population (1798), the law first came under examination during the discussions in England on free trade and the corn laws. It is also called the law of decreasing returns and the law of variable proportions.³³

While the law was originally conceived to explain day laborers working in wheat fields, it can be used in the design world, as well. Here’s an example from a mailing I received with my credit card statement years ago–it’s an ad for a Coleman multi-function “TV lantern,” easily one of the most ridiculous and impractical devices I’ve ever seen.

The law of diminishing returns requires that one “factor of production” increase while the others remain constant. In the world of product design, it’s safe to refer to these “factors of production” simply as a product’s features. A good, dependable camping lantern has one primary feature–a light, used to illuminate things. This lantern, however, has four primary features:

1. Television
2. Flashlight/lantern
3. Radio
4. Siren

The “overall return” referred to in the law is, in this case, the product’s usability. Compared to an ordinary battery-operated camping lantern, which simply switches off and on, this particular lantern has quite a few other fiddly bits that a user has to concern himself with–if it has a bad interface³³, then its usability is severely reduced until the owner gets over the learning curve–assuming that he or she doesn’t just give up and throw it out or return it.

The problems don’t end there. Assuming that this lantern is roughly comparable to other lanterns in terms of its size, its added baggage (in terms of its extra internal electronics) has to have a huge negative impact on its weight, battery life and light intensity. Plus, if one component breaks, the entire device is reduced to the status of “junk that gathers dust in a corner of the basement.”

This whole concept is in line with the idea of affordance, which Lidwell, Holden and Butler do a great job of concisely summarizing in their book Universal Principles of Design:

[Affordance is] a property in which the physical characteristics of an object or environment influence its function. Objects and environments are better suited for some functions than others. [...] When the affordance of an object or environment corresponds with its intended function, the design will perform more efficiently and will be easier to use.³³

The idea here is simple: When an item’s physical characteristics match the environment it will be used in, the item will inherently be easier to use. To apply this to our example, a simple camping lantern wins because it was designed to perform one function (provide light), whereas the Coleman TV lantern is problematic because it does too many things that a lantern does not ordinarily do.  These additional features introduce multiple failure points into the device, making the likelihood that it will break (or simply work poorly) skyrocket.

This is the problem across the board with most of the SkyMall products referenced back at the beginning of this article. A decorative planter does not ordinarily contain a catbox; therefore, it is tacky. A cane does not ordinarily flash, blink or make sounds; therefore, it is more prone to failure. A back massager is not ordinarily a gigantic piece of metal or plastic; therefore, it is unwieldy and difficult to use. And so on.

As I have been writing this essay, I’ve simultaneously been mulling over what, exactly, constitutes a good invention, since we seem to be surrounded by so many bad ones. There seem to be two primary types of “good” inventions out there:

1. Items that have one single primary function
   These can range from the relatively simple (light bulb, aerosol can) to the banal (television, escalator) to the high-tech (TiVo, car). Each of these items’ primary functions can be described in one single phrase:
   • A light bulb is a replaceable source of illumination.
   • A TiVo records television broadcasts.
   • An escalator is a staircase that hastens movement to another floor.
2. Simple items that lend themselves to a variety of functions
   Cotton balls, paper clips, paper, wire, and similar items are all examples of this type of invention. In many cases these might even be considered “elements” of other inventions–that is, they are the smallest discreet man-made units that an invention can be broken down into.

This is perhaps an oversimplification, but the point remains that a “bad” product³³ quite often tries to do too much and as a result ends up doing virtually nothing at all.3

1. Quoted from Encyclopedia.com.333
2. I’m fairly certain that there is probably no “multi-function camping lantern design usability expert” out there, though I could be wrong.333
3. Lidwell, William, et al. Universal Principles of Design. Gloucester: Rockport, 2003. 20-21.333
4. In this context, I’m excluding products that are inherently flawed, of poor construction, broken or dangerous.333

3