I finally broke down and decided to get a smart phone for myself. While I find it really useful, I can't help wondering if any research has been done on the "gorilla arm effect" of holding a smart phone at a certain angle while trying to read something or going through an app. It won't be too prevalent if the phone screen is small enough that you can hold it with one hand and click with your thumb but having a smartphone with a large screen (4.3 inches), I can't help wonder what would be the impact as screens keep getting bigger (unless you have large hands).

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    They keep getting larger to a point, then they jump the invisible divide and become tablets, where two hands is expected. Commented Dec 9, 2011 at 21:41
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    Screens on phones won't keep getting bigger; much beyond 4 inches and it no longer fits in your pocket. A 5 inch touch enabled thing isn't really a smartphone or a tablet, it's just junk with a nice OS. Even 7 inch tablets have a questionable feature. useit.com/alertbox/kindle-fire-usability.html
    – Ben Brocka
    Commented Dec 9, 2011 at 22:52
  • I am sorry I didnt respond earlier ,I am aware of what the Gorilla arm effect is but I was curious to know peoples views of how that issue might affect user interaction as screens continue to bigger and bigger as users will be forced to use two hands.I do agree after a certain size,the phone can no longer be considered as a phone and passes into the boundary of tablets but who is going to tell cell phone manufacturers that?
    – Mervin
    Commented Dec 29, 2011 at 21:26

1 Answer 1


Here you will find some papers mentioning the "gorilla arm effect". It's a pitty that some of them are not free to download.

Some more articles and references to this syndrome:

The last article defines the Gorilla Arm effect thusly:

“Gorilla arm” was a side-effect that destroyed vertically-oriented touch-screens as a mainstream input technology despite a promising start in the early 1980s.

Designers of touch-menu systems failed to notice that humans aren’t designed to hold their arms in front of their faces making small motions. After more than a very few selections, the arm begins to feel sore, cramped, and oversized—the operator looks like a gorilla while using the touch screen and feels like one afterwards. This is now considered a classic cautionary tale to human-factors designers; “Remember the gorilla arm!” is shorthand for “How is this going to fly in real use?”.

And finally:

Gorilla arm is not a problem for specialist short-term-use uses, since they only involve brief interactions.

So, as long as we keep having "short-term" interactions with our handhelds —or as long as they keep getting lighter—, this will not be a problem. The Gorilla Arm effect though is a nice reminder on how promising interaction patterns can go wrong.

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