Switch access scanning

Last updated February 25, 2019

Switch access scanning is an indirect selection technique (or access method), used by an assistive technology user, including those who use augmentative and alternative communication (AAC) to choose items from the selection set.^[1]^[2] Unlike direct selection (e.g., typing on a keyboard, touching a screen), a scanner can only make selections when the scanning indicator (or cursor) of the electronic device is on the desired choice.^[3] The scanning indicator moves through items by highlighting each item on the screen (i.e., visual scanning), or by announcing each item via voice output (i.e., auditory scanning), and then the user activates a switch to select the item.^[4]^[5] The speed and pattern of scanning, as well as the way items are selected, are individualized to the physical, visual and cognitive capabilities of the user.^[6] While there may be different reasons for using scanning, the most common is a physical disability resulting in reduced motor control for direct selection.^[3]^[7] Communication during scanning is slower and less efficient than direct selection and scanning requires more cognitive skill (e.g., attention).^[4]^[5] Scanning using technology has an advantage allows the user to be independent in controlling the assistive technology for those with only one voluntary movement.^[4]

Assistive technology is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities or elderly population while also including the process used in selecting, locating, and using them. People who have disabilities often have difficulty performing activities of daily living (ADLs) independently, or even with assistance. ADLs are self-care activities that include toileting, mobility (ambulation), eating, bathing, dressing and grooming. Assistive technology can ameliorate the effects of disabilities that limit the ability to perform ADLs. Assistive technology promotes greater independence by enabling people to perform tasks they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to, or changing methods of interacting with, the technology needed to accomplish such tasks. For example, wheelchairs provide independent mobility for those who cannot walk, while assistive eating devices can enable people who cannot feed themselves to do so. Due to assistive technology, people with disabilities have an opportunity of a more positive and easygoing lifestyle, with an increase in "social participation," "security and control," and a greater chance to "reduce institutional costs without significantly increasing household expenses."

Augmentative and alternative communication (AAC) is an umbrella term that encompasses the communication methods used to supplement or replace speech or writing for those with impairments in the production or comprehension of spoken or written language. AAC is used by those with a wide range of speech and language impairments, including congenital impairments such as cerebral palsy, intellectual impairment and autism, and acquired conditions such as amyotrophic lateral sclerosis and Parkinson's disease. AAC can be a permanent addition to a person's communication or a temporary aid.

A physical disability is a limitation on a person's physical functioning, mobility, dexterity or stamina. Other physical disabilities include impairments which limit other facets of daily living, such as respiratory disorders, blindness, epilepsy and sleep disorders.

Scanning patterns

A scanning pattern refers to the way items in the selection set are presented to the user. It allows for easier item selection as the scanning is systematic and predictable.^[3] Three primary scanning patterns exist:

In circular scanning, individual items are arranged in a circle (like the numbers on a clock face) and the scanning indicator moves in a circle to scan one item at a time. Although circular scanning is visually demanding, it is the simplest scanning pattern as it is cognitively easy to master.^[2]^[3]
In linear scanning, items are usually arranged in a grid and the scanning indicator moves through each item in each row systematically.^[2] Although linear scanning is cognitively more demanding than circular scanning, it is relatively straightforward and easy to learn.^[8] However, it may be inefficient if there are many items in the set (e.g., in a grid consisting of 8 items per row, if the desired item were the 7th item in the 4th row, the scanning indicator would have to scan through 30 undesired items first before reaching the desired item.
In group-item scanning, items are grouped (e.g., by row, column, or other meaningful categories) and the scanning indicator will first scan by groups. Once the scanner selects the group his desired item belongs to, the scanning indicator will scan each item in the selected group. Among the variations of group-item scanning, the most common is row-column scanning where the items are grouped in rows.^[2]^[8]

Scanning control techniques

Scanning control and item selection occurs through switch activation in three general ways:

In directed (or inverse) scanning, the indicator will only scan in the preset pattern when the user holds down a switch. Selections are made when the switch is released.^[2]^[9]
In automatic (regular or interrupted) scanning, the indicator scans in the preset pattern on its own and item selection occurs when the scanner hits a switch.^[5]^[7]
In step scanning, the user controls each movement (or step) of the scanning indicator through its preset pattern by hitting a switch. To select an item, the AAC user hits a second switch once the indicator reaches his desired item. Because of the constant switch activation, this method might be too fatiguing for the certain scanners, including those with Amyotrophic lateral sclerosis, but is easier cognitively.^[5]^[7]^[10]

Amyotrophic lateral sclerosis (ALS), also known as motor neurone disease (MND) or Lou Gehrig's disease, is a specific disease which causes the death of neurons controlling voluntary muscles. Some also use the term motor neuron disease for a group of conditions of which ALS is the most common. ALS is characterized by stiff muscles, muscle twitching, and gradually worsening weakness due to muscles decreasing in size. It may begin with weakness in the arms or legs, or with difficulty speaking or swallowing. About half of people develop at least mild difficulties with thinking and behavior and most people experience pain. Most eventually lose the ability to walk, use their hands, speak, swallow, and breathe.

Notes

↑ Beukelman & Mirenda, 2005, p. 92
1 2 3 4 5 Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9.
1 2 3 4 Beukelman & Mirenda, 2005, p. 97
1 2 3 American Speech-Language-Hearing Association. (2004) Roles and Responsibilities of Speech-Language Pathologists With Respect to Augmentative and Alternative Communication: Technical Report
1 2 3 4 Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4.
↑ Beukelman & Mirenda, 2005, p. 97-101
1 2 3 Radomski, Mary Vining & Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. pp. 524–25. ISBN 978-0-7817-6312-7.
1 2 Beukelman & Mirenda, 2005, p. 98
↑ Beukelman & Mirenda, 2005, p. 100
↑ Beukelman & Mirenda, 2005, p. 101

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References

Beukelman, D. & Mirenda, P. (2005 Augmentative and Alternative Communication: Supporting Children and Adults with Complex Communication Needs (3rd edition) Baltimore: Brookes.

External links

A Demonstration of scanning

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[1] Beukelman & Mirenda, 2005, p. 92

[vinson-2] 1 2 3 4 5 Vinson, Betsy Partin (2001). Essentials for speech-language pathologists. Cengage Learning. pp. 150–51. ISBN 978-0-7693-0071-9.

[b97-3] 1 2 3 4 Beukelman & Mirenda, 2005, p. 97

[asha-4] 1 2 3 American Speech-Language-Hearing Association. (2004) Roles and Responsibilities of Speech-Language Pathologists With Respect to Augmentative and Alternative Communication: Technical Report

[hedman-5] 1 2 3 4 Hedman, Glenn (1990). Rehabilitation Technology. Routledge. pp. 100–01. ISBN 978-1-56024-033-4.

[6] Beukelman & Mirenda, 2005, p. 97-101

[radom-7] 1 2 3 Radomski, Mary Vining & Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. pp. 524–25. ISBN 978-0-7817-6312-7.

[b98-8] 1 2 Beukelman & Mirenda, 2005, p. 98

[b100-9] Beukelman & Mirenda, 2005, p. 100

[10] Beukelman & Mirenda, 2005, p. 101