Electric Toothbrush & Function Allocation
Miranda Capra / Consumer Products / Human FactorsSeveral months ago I bought my first electric toothbrush, and I have to admit that I’m in love. Not only is it a great toothbrush, but it’s a great example of a classic Human Factors design issue: function allocation between humans and machines. This is an issue that dates back to at least 1951 with Fitts Lists, and HABA-MABA lists, such as:
- Humans are best at (HABA) information retrieval using context and associations, machines are best at (MABA) information retrieval based on long lists and structured information.
- Humans are best at creative and adaptive tasks, machines are best at precise and repetitive tasks.
The lists change as machine capabilities change, but they are helpful when assessing a complex system and looking for places where machine automation can help, such as scanning barcodes at the grocery store instead of typing in prices, and where they introduce new problems, such as airplane pilots having difficulty staying awake during long flights because so many tasks have been automated. So how does this apply to my toothbrush?
The toothbrush takes care of the aspects of brushing my teeth that a machine is best at.
- It vibrates the head of the toothbrush, moving the bristles across my teeth much faster than I could ever hope to do (machines are better at small, repetitive motions).
- It automatically stops after the ADA-recommended 2 minutes, so I keep brushing until it stops (machines are better at judging time).
- It has a special beep (really a brief change in the vibrating speed) every 30 seconds that lets me know when to switch quadrants, so that I don’t over- or under-brush different areas (again with the time).
- It even has a quick 1- minute mode for days when I’m in a rush to make sure I get at least some minimal brushing in, since humans are even worse at judging time when they’re stressed (machines don’t get stressed about being late).
That leaves me, the human, to focus on the things that I’m better at, like slowly moving the toothbrush and getting that brush head into the back corners of my mouth. I get better brushing coverage, since I’m not distracted by trying to also keep up the repetitive brushing motions (humans aren’t very good at doing multiple things at once).
Cleaner teeth and a quick lesson in function allocation. I love it!
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Kirk Abraham
(another) excellent post! Thanks for supporting what we already know, but have difficulty articulating or supporting WHY, ie, Fitts Lists.
If you could’ve seen the look on my brides’ face when I returned from a dentist appt. circa 2004 with a > $100 tooth brush…a Sonicare. We’re now on our SECOND (wore 1st one out)!!
Who knew oral hygiene could be so educational? I can hardly wait for a post on lawn care via weed whacker!
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Kirk Abraham
One of my all time favorite quotes applies, “Machines are fast, accurate and stupid. Humans are slow sloppy & brilliant.”
Also, have you noticed how often we try to exact the OPPOSITE results, eg, expect humans to act like machines and machines to become & act more human? Every single day…
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