On today's keyboards, the two Shift keys are somewhat elongated horizontally, but otherwise look much the same as any other key on the keyboard. However, in times past it was not altogether unusual for Shift keys to have quite a different profile: overall the key was wider than the other keys, but the left and right edges were recessed. The centre of the key jutted out from this recessed base, with a pressable surface that was about the same size, or maybe only slightly wider, than a normal alphanumeric key. Below is an example of such a keyboard (namely, the famous space-cadet keyboard of 1978):

Photograph of a space-cadet keyboard showing the partially recessed Shift keys Source: Space-cadet.jpg by Shieldforyoureyes Dave Fischer / Retro-Computing Society of Rhode Island. Licensed under the CC BY-SA 3.0 Unported licence.

Now, I'm not saying that such Shift keys were ubiquitous in the past, nor that they are never found at all on modern-day keyboards, though in my experience they were much more common thirty or forty years ago than they are now. I'd like to know the reason that these Shift keys (and no other keys on the keyboard) were designed this way and why this design seems to have disappeared. Was there a particular ergonomic reason for the shape that applied back then but that is no longer relevant today?

I suppose it could be argued that the unusual shape makes the keys easier to distinguish when touch-typing, though I've personally never had any problems finding the Shift key when my fingers are on the home row, and besides, the recessed edges seem to make the key harder to strike reliably. Moreover, ergonomic aids don't seem to be high up on the list of features of ancient keyboards—for example, I don't recall seeing any of them with bumps on the F and J (or D and K) keys that are used today to help touch-typists find the home row. If there really is some ergonomic benefit to this Shift key shape, then why don't most modern keyboards (even relatively expensive ones) continue to use it?

Is it possible that this Shift key design had its roots in mechanical typewriters, and got mindlessly carried over to computer keyboards? If so, what mechanical benefit did this design have, and why was it applied only to the Shift keys and not to other large keys such as the Return key or (on some typewriters) the Tab or Backspace keys?

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    Mindlessly? The Selectric was a huge success and (as far as I know) state of the art. – Thorbjørn Ravn Andersen Oct 6 '20 at 9:28
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    The Model F keyboard used such keys for all unusually-shaped keys, not just Shift. I wondered if there was a mechanical reason for the Shift key to be narrower (because it actuates a lever which requires quite a lot of force), but I’ve seen mechanical keyboards with a wide Shift key without the Selectric-style shape; and given how the Selectric typing element works, I don’t think mechanical aspects would be a factor in the key shape. – Stephen Kitt Oct 6 '20 at 9:48
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    @StephenKitt Well, there maybe is: The levers under the keys on a Selectric are guided in a comb-shaped plate - If you press (or were able to press) large keys off-centre, these are likely to bind (or at least rub against the guide) in not-so-well-maintained machines. I really think the key shape was invented to educate typists to press the centre of the key. – tofro Oct 6 '20 at 10:45
  • A lot depends on whether the designer was a touch typist or actually trialled the layout with a touch typist. Some keyboard designs (like the MS split keyboard) have obviously not been trialled with high speed touch typists. – cup Oct 7 '20 at 6:21
  • This key format is still in use today. For example, my Microsoft Sculpt Comfort Keyboard has this recess on the right side on the Caps Lock key. – Jonathan Oct 13 '20 at 7:23

Simple answer: When there is a definite place where the key has to be pressed, there is much less probability that the key is pressed off-center and binds, thus you could possibly do without the wire linkage that prevents that on most modern keyboards.

  • If that's the case, why bother making the key wider to begin with? And also, why didn't they use a wire linkage back then? Had such a mechanism not been invented? – Psychonaut Oct 6 '20 at 11:32
  • @Psychonaut Well, some went for smaller Shift keys - have a look at compact keyboards or even modern notebooks. Typists weren't happy. And, of course, if you can live without a mechanism in a commercial product, you'll do. Such mechanisms drive cost up and were hard to assemble manually (today, that's probably a piece of cake for the assembly line). – tofro Oct 6 '20 at 11:42
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    People come up with retrospective technical explanations of 1960s key widths and spacings (such as the "stepped" shift and lock keycaps on the Selectric), but the literature of the time (particularly W. H. Harkins, "Switch system for consoles". Industrial Design. 1965.) said that these things were "due to design conventions rather than empirical data". Enjoy dx.doi.org/10.1177/001872087201400401 . – JdeBP Oct 6 '20 at 14:26
  • @psychnaut No doc but keyboards with rectangular keycaps from my Mom's portable Olivetti (sleek & modern) to office keypunch & Selectrics & Wang workstations, to DEC, TI, CDC, etc., consoles, keyboards, and/or portable terminals (yeah portable TI dialup w/ thermal paper), to luggable Compaq & IBM PCs, etc., have some keys sized to fill a space that ensures evenness. Notice inner rectangle = original typewriter (less spacebar) in OP. On my current early '90s keyboard (104 layout but split + 4 extras) only caps lock keycap is stepped (only on 'A' side) & one shift keycap is wider than the other – BillR Oct 7 '20 at 0:12
  • Seems to have been a thing - see for example this Flexowriter keyboard - which I assume to be a fairly late model, since it's not built like a World War II tank. – another-dave Oct 7 '20 at 2:18

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