Mobile6

Do users interact with their mobile devices with their dominant hand ?

A key to success, when designing anything that will be used by a human being, is understanding how it will be used. Since I believe understanding behavior implies taking in account the natural contexts in a holistic approach, while cutting up the problem in digest chunks, I decided to conduct a series of humble studies, which hopefully will provide interesting and unexpected insights into mobile user behavior.

Part 3 : Left or right hand ?

Left vs. Right Hand mobile interaction

My initial study on how users interact with their mobile devices did not cover left or right handed usage. Although I did not plan to do so, I completed my data set with an additional observation batch. So first, let’s have a look at what convinced me to add this to the metro project.

On the subject of right of left hands, the initial study published on UXmatters has a little to say : about 2/3 of users used their right thumb on the screen, and 1 third used their left thumb. This is surprising, since roughly 12% of men and 10% of women are left-handed.

An interesting survey from Ben Schwarz asked users whether they were right or left-handed and which hand they used to use their phone. Although a survey might reflect what people think they’re doing more than what they actually do, the results seem to indicate right or left-handedness doesn’t impact directly the way users hold their phones :

The percentages corresponding to the answer “both hands” is similar to the actual both hands use observed, but we can’t assume it doesn’t include some cradling as well. The same way, holding the phone with one hand doesn’t tell us if they actually interacted with their phone with one hand, or if they actually used they other hand for the interaction. Nevertheless, both the observation results and this data encourages UX designers to take in account left handed use more, and as Ben points out, might reconsider their accessibility zones to adapt more to either hand’s use.

However, one thing bothered me : Steven’s study focused on the way people are holding their devices, and the information covers interaction aspects roughly. Ben’s study asks people to say which hand they use their phone with, so interpretation of the answers as being the holding hand or the interacting hand depends on the participants. Besides, users are not aware of what they are doing, and they might give inaccurate answers.

Because of this, I decided to gather additional observations to my previous batch. This additional data is coherent with the previous set. The proportions of positions observed differ slightly.

Sitting Standing Walking
 Additional data 35.66% 42.12% 22.22%
 First data set 34.38% 53.13% 19.92%

the ways of holding the devices are also very similar

First dataset Additional dataset
One hand 65.47% 53.90%
Cradle 20.08% 19.24%
2 hands 14.45% 26.87%

But let’s have a look at the details which interest us here, and were only gathered in the new dataset. First, let’s have a look at which hand the users hold their device with :

Sitting Standing Walking Total
Left hand 28.84% 33.46% 34.33% 32.01%
Right hand 31.16% 43.70% 52.24% 41.13%
Both 40.00% 22.83% 13.43% 26.87%

If you look at the interacting hand however, the results are quite different. When sitting, users seem to hold their phone with both hands, or regardless with the right or left hand. When walking and standing, the number of people observed holding their phone with both hands decreases, apparently in favor of holding their mobile device in their right hand.

Sitting Standing Walking Total
Left hand 13.49% 25.98% 32.09% 22.89%
Right hand 66.05% 57.48% 57.46% 60.53%
Both hands 20.47% 16.54% 10.45% 16.58%

Users who hold their phone with both hands sometimes interact with only one of them.

In terms of interaction, the right hand seems to be used more often. The proportions vary depending upon whether the users are sitting, standing or walking. Users seem more likely to use either hand when walking, while the right hand seems to be the preferred choice when sitting.

In the following table, we excluded from the data only two handed interactions.

holding_hand

Sitting Standing Walking
Hold left 48.06% 43.37% 39.66% 43.76%
Hold right 51.94% 56.63% 60.34% 56.24%

In terms of holding, the split seems to be about 50/50 between left and right, with slightly more chances to see users hold a phone in their right hand, rather than the left, while walking.

In terms of interacting however, we gather something very different.

interacting_hand

Sitting Standing Walking
Interact left 16.96% 31.13% 35.83% 27.44%
Interact right 83.04% 68.87% 64.17% 72.56%

Globally, it’s more likely to see users interact with their mobile device with their right hand rather than the left. This is particularly true when users are sitting. When walking, there is very close to the one observed for holding. We also know that one handed use is more common when walking from our previous study, so it makes sense to find similar numbers.

If we consider only one handed use of the phone, so that the holding hand is also the interacting hand, we can see that globally, the right hand seems to be dominant whatever the position of the user.

Sitting Standing Walking
One handed: left 22.37% 33.33% 37.14%
One handed: right 77.63% 66.67% 62.86%

onehanded

These percentages are different from the average left/right-handed people. As mentioned earlier in this article, roughly 12% of men and 10% of women are left-handed. This means maybe 10% to 30% don’t use their right hand, although they probably were right handed. It might be even more, and go both ways, since we didn’t ask each observed user what their handedness was.

We saw previously that there was a relation between the location and how users holding and interact with the mobile devices. A statistical khi² test reveals no such relation between the location and which hand users use to interact with their mobile devices.

So, left hand use isn’t really a 50/50 split, once you distinguish holding and interacting. The results are sufficiently detailed however for designers to decide whether they should design for both hands or stick to right handed use. If your app is designed to be used while sitting mainly, designing for left handed use might be less critical than when designing an app that is meant to be used outdoors, on the move, or while standing.

Rather than telling designers what they should do, I mostly invite them to consider in what context their app or site will be used, and as a result, what is the best approach for each particular project.

One question remains unanswered though, why do users interact hold or interact with their phones with one hand or the other. What are they doing that requires the attention of their hands? While the metro studies go on with a look at mobile users attention spans, the context of use will be one more aspect that we shall deal with in an upcoming article.

Meanwhile, feel free to share your thoughts on the subject, and stay tuned for the next article of the metro studies.

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