…you have chosen the types of gesture you will employ for each target, as well as the dimensions of these targets. Now, you are now in a phase of the project where decisions need to be made regarding adequate spacing sizes between adjacent-targets. Choosing spacing sizes between adjacent-targets is an important decision, as it may determine the levels of comfort, and efficiency with which your users are able to get things done on your interface.
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As a result of the ageing process, sensory and psychomotor capabilities undergo several declines, and these alterations may render common interfaces to be unusable. In this context, it is of paramount importance to take these age-related changes into account when designing smartphone interfaces for older adults. Furthermore, existing smartphone OS guidelines do not provide guidance regarding spacing sizes between adjacent-targets for specific audiences, such as older adults.
It is commonly accepted that visual acuity (Fisk, Rogers, Charness, Czaja, & Sharit, 2009), movement control, hand-eye coordination, hand dexterity (Carmeli, Patish, & Coleman, 2003) and touch sensitivity (Carmeli et al., 2003; Fisk et al., 2009; Nusbaum, 1999; Wickremaratchi & Llewelyn, 2006) suffer considerable losses during the ageing process. Additionally, vision and psychomotor capabilities can be further compromised by common diseases among older adults such as Age-related Macular Degeneration, cataracts, presbyopia glaucoma — relative to visual abilities; and multiple sclerosis, arthritis, osteoporosis, stroke and Parkinson’s disease — related to psychomotor issues. Movement can be severely affected by these diseases, causing symptoms such as weakness, numbness, loss of muscle coordination, pain, stiffness, tremors, rigidity and slow movement (Kurniawan, 2008). Thus, making it harder to see small targets and distinguish them when spacing between targets is very reduced.
Previous research has explored the influence of spacing dimensions between adjacent-targets on participants’ performance. (Colle & Hiszem, 2004) and (Sun, Plocher, & Qu, 2007) found that with younger adults the spacing between tap targets had no significant effect on participants’ performance. In addition, (Sun et al., 2007) revealed that, contrary to what was expected, performance did not improve as spacings became larger. Similarly, (Jin, Plocher, & Kiff, 2007) found that older adults had longer reaction times with larger spacing sizes between tap targets, and that spacing should be between 2.17 and 12.7 mm. Additionally, existing smartphone OS guidelines recommend spacing of 1.5 to 2 mm, which is lower than those found by (Jin et al., 2007) for older adults using a larger fixed touchscreen.
Regarding spacing sizes between adjacent-targets, our own work showed that spacing sizes did not influence participants performance as much as target sizes did. It seems that older adults were able to easily acquire tap targets with spacings between each other of 0 to 10.5 mm, and swipe targets with spacings of 0 to 7 mm between each other.
Depending on the screen real-estate available, allow for 0 to 10.5 mm spacing between adjacent tap targets, or for 0 to 7 mm spacing between adjacent swipe targets.
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Carmeli, E., Patish, H., & Coleman, R. (2003).The Aging Hand. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 58, M146-M152. doi: 10.1093/gerona/58.2.M146
Colle, H. A., & Hiszem, K. J. (2004).Standing at a kiosk: Effects of key size and spacing on touch screen numeric keypad performance and user preference. Ergonomics, 47(13), 1406-1423. doi: 10.1080/00140130410001724228
Fisk, A. D., Rogers, W. A., Charness, N., Czaja, S. J., & Sharit, J. (2009).Designing for Older Adults: Principles and Creative Human Factors Approaches, Second Edition (Human Factors & Aging): CRC Press.
Jin, Z. X., Plocher, T., & Kiff, L. (2007).Touch screen user interfaces for older adults: button size and spacing. Universal Acess in Human Computer Interaction Coping with Diversity, 4554, 933-941.
Kurniawan, S. H. (2008). Web Accessibility: A Foundation for Research. In S.-V. London (Ed.), Human-Computer Interaction Series (pp. 47-58).
Nusbaum, N. (1999). Aging and sensory senescence. Southern medical journal.
Sun, X., Plocher, T., & Qu, W. (2007). An empirical study on the smallest comfortable button/icon size on touch screen. Paper presented at the Proceedings of the 2nd international conference on Usability and internationalization, Beijing, China.
Wickremaratchi, M. M., & Llewelyn, J. G. (2006). Effects of ageing on touch. Postgraduate medical journal, 82, 301-304. doi: 10.1136/pgmj.2005.039651