Naoto Fukasawa’s toaster for ±0 (sold only in Japan) has one slot. The rationale behind only one slot he explains in his self-titled design book: Naoto Fukasawa
Toasting one slice of bread at a time operates as a gesture of generosity. He would toast a slice of bread for his wife, then a slice for himself.
To me, it works as a perfect example of cognitive engineering, which I intend to study in grad school, and integrate into more of the things in the built environment as a designer.
If you have a two-slot toaster, you’re more likely to toast two slices of bread, based on the research of Brian Wansink of Cornell University’s Food and Brand Lab, and therefore eat two slices of bread. If you have a one-slot toaster, you have to think about toasting that second slice of bread after toasting the first, and therefore are less likely to mindlessly eat a second slice.
While less convenient for making a sandwich, and personally I’m a proponent of the toaster oven, it does make a wonderful example piece, and in the writeup on the website, it specifically says it’s not so much for the kitchen, but for the table.
In a larger context, this kind of thinking can be brought to many more things: a handy switch and indicator light integrated into the electrical outlet makes it easier and more likely you’ll turn off the unused charger (which draws a tiny current, even when not charging anything). Smaller plates and silverware make you eat less.
We’re being subtly manipulated half randomly and half by people on Madison Avenue (for profit) – and my take is to put some intelligence into this and do some manipulating for good, going back to the "using evil uses of psychology for good" paradigm. O|O