Spear’s Spellmaster: Poka-yoke in the classroom

Back in September we looked at Mentor Teaching Machines, a clever type of non-linear textbook from the early 1970s which guides/constrains the user’s progression, in the process diagnosing some common types of misunderstanding and ‘remedying’ them. The comments were enlightening, too: there’s a lot more history to programmed teaching texts and programmed instruction than I realised, and I will certainly be covering some of this, and what useful design principles and inspiration can be drawn from it, at some point.

Now, this is not in the same league, but interesting nonetheless: a ‘game’ to teach children (4 years onwards) spelling using a poka-yoke technique. The Spellmaster, from J W Spear & Sons – the example here is from 1980 (the Enfield factory was closed after a Mattel takeover in 1994) featured eighty plastic letter tiles, Scrabble-like but larger, with raised pegs underneath, a different pattern for each letter.

Spear's Spellmaster

Spear's Spellmaster

Spear's Spellmaster

Spear's SpellmasterSpear's Spellmaster

The letter tiles are used to spell the names of objects and concepts (colours, numbers) illustrated on punched cards which fit onto a backing board, the tiles only fitting in their spaces correctly if the pegs pattern aligns perfectly with the punched holes. If the wrong letter is used, the tile doesn’t fit properly and sits at an angle rather than snapping neatly into place. The ‘snap’ of a correctly positioned letter is actually pretty satisfying – surprisingly so, given the combination of plastic (urea formaldehyde, I think) and 30-year old cardboard.

Spear's Spellmaster

Spear's Spellmaster

Spear's SpellmasterSpear's Spellmaster
Left: The wrong tile – the pegs do not align with the punched holes. Right: The correct tile – everything lines up. Below: The wrong tile here – note the extra peg on the left-hand edge of the tile, which doesn’t match up with the punched hole, and leads to the tile not sitting down properly.
Spear's Spellmaster

Spear's Spellmaster

Letters which could work either way up, such as ‘o’ and ‘s’ have – as would be hoped – symmetrical peg patterns. It’s a simple system, but it’s clever and while not offering any ‘remedial’ function to the child, I would think it’s not too likely that many children would try all 25 other letters assuming the first one didn’t fit. Hence, there is some bias against pure trial-and-error. It’s interesting to think how immediately we might consider a computer-based solution to this kind of design brief today, where a purely physical one would work very well and give a different kind of tactile satisfaction.

Spear's Spellmaster

Spear's Spellmaster


  1. Matt Platte

    we might consider a computer-based solution to this kind of design brief today

    What you meant: we might consider an electronic computer-based solution to this kind of design brief today…

    Because the Spellmaster is, indeed, a computer as was Mr. Jaquard’s programmable looms.

    Somewhere in my attic is a wooden box that holds a couple hundred cards, each card with various tabs and holes along the top. Poking a metal rod across the top of the box would select different sets of cards. Should I find it anytime soon, I’ll send a photo or three.

  2. Dan

    Thanks Matt, that’s a good point. Indeed, right in front of me on the desk is a library book with a punched index card.

    Punched card from Brunel University Library

    To some extent most of the examples of ‘behaviour-controlling’ technology and design could be thought of as ‘programming’ the interaction between user and system, even where the result isn’t ‘guaranteed’ (most methods which rely on persuading the user rather than forcing him/her). Is design basically woolly programming?

    But are they all ‘computers’? I’m not sure. Do they manipulate data according to a set of instructions/criteria?

    Maybe the difference comes down to the extent to which different outcomes can be produced based on selected criteria. The Spellmaster came with one backing board, twenty cards each with five words on, and eighty letter tiles, and the ‘programmed’ aspect only works when the system is used together as intended. If you use the tiles without the word cards, you can spell anything. But with the cards in place, you are given potentially 100 words to spell, and correct spellings work and wrong ones don’t.

    Compared to, say, the cut-off corner on a SIM card or 3½” floppy disk – which, despite also working on a principle of ‘form-based physical interference to ensure correct positioning and orientation of a component’ – it seems that one system (the Spellmaster) is far closer to being a computer than the other.

  3. “The ’snap’ of a correctly positioned letter is actually pretty satisfying”

    this phrase took me straight back in a vivid flashback. I really had forgotten about these sets.

    Nostalgia aside I quite agree with the point you’re making, that there are physical interfaces out there that have qualities beyond the HCI/electronic efforts we might initially assume to be the answer. I suspect you might be anticipating the design trends which come after the wave of physical/ubiquitous computing currently buzzing around dies down.

  4. KK

    I am a primary school teacher and have in my possession the cards for the now antique Spell Master spelling activity. Somewhere along the way I misplaced the tiles. I am very reluctant to throw away the cards because I think it is an excellent learning tool for the grade one classroom. If anyone is willing to sell me their tiles I would very much appreciate this.

    Thanks, K

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