ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction...

ICCHP 2006 – Young Researchers – Simon JudgeThe application of Human Computer Interaction principles to Assistive Technology

The application of Human Computer Interaction principles

to Electronic Assistive Technology

Simon Judge MEng, MIET

Clinical ScientistAccess to Communication and Technology, Birmingham, UK


Contents

• My role• The use of Human Computer

Interaction (HCI) models for Electronic Assistive Technology (EAT)– Examine literature behind an EAT

activity (switch access)– Introduce the Model Human

Processor (MHP) as a potentially relevant model

– Provide examples of applicability• Implications for Assistive Technology• Future suggested work/direction


My role

• Clinical Scientist• Within specialist NHS Electronic

Assistive Technology (EAT) team in the UK

• Clinical role: wide range of client contact (any age, any condition)

• Assess for and provide:– Communication aids– Environmental Control systems– Computer Access equipment

• A unique insight into man-machine interaction and the use of AT devices


Hypothesis

• The evidence base for Electronic Assistive Technology (EAT) is small and immature

• Technology and techniques used in other fields are not readily transferred to EAT products or practice

• EAT provision is not necessarily based on evidence or theory

• To develop the EAT evidence base, the field should use models and theories from other fields.


Assistive Technology

• Assistive Technology field is concerned with:

“Assistive Technology (AT) is any product or service designed to enable independence for disabled and older

people." King's Fund Consultation (14th March

2001)


Electronic Assistive Technology

• No clear definition of Electronic Assistive Technology (EAT). To derive a definition:

“Electronic systems designed to enable independence for disabled and older

people”


Human Computer Interaction

• The Human Computer Interaction (HCI) field is involved with:

“Human Computer Interaction is a discipline concerned with the design,

evaluation and implementation of interactive computing systems for

human use…” ACM SIGCHI


HCI - EAT

• HCI should, thus, obviously be heavily involved with EAT?

• Lets use switch access as an example…


Switch Access 101

• Part of a spectrum/bandwidth of input• Using a single binary source to

transmit information [ DEMO ]

Input Bandwidth


Switch Access

• Within EAT switch access is an important method of access

• Specialist services have a lot of contact with switch access. Generally single switch auto-scan is the default.

Jones and Stuart (2004) 1

• At the moment switching is a ‘clinical black art’

• Even the literature is not based on evidence.

Robbers and McDonald, Communication Matters (2005)


Switch Access – Questions:

• What is the most effective type of switch access for different people?

• What are the pre-requisite skills required to scan

• What is the cognitive load of different scanning techniques

• How is input bandwidth laid out at the switch end?

Input Bandwidth


Switch Access Evidence

• Comprehensive Literature Search• General search terms• Published and unpublished work:

– 22 papers (!) of over 1000 searched– 17 published in peer-reviewed journals– ~1% of published work on Assistive

Technology.– Few directly related to switch access– Few involved user trials (mostly case

studies)• Equivalent (independent) work found similar

results - few papers and lack of evidence in literature.

Robbers and McDonald (2005)


Models

• Models allow a theory to be better understood:

“By it’s nature a model is a simplification of reality. However, a model is useful if it helps in

designing, evaluating, or otherwise providing a basis for understanding the behaviour of a

complex artefact such as a computer system.”MacKenzie (2003)

• Few, if any, models in Assistive Technology.• Models used extensively to evaluate HCI tasks• Model Human Processor is one such model


Model Human Processor (MHP)

• Three components:– Perception– Cognition– Motor

• Principles for each component and rules which describe components and their interaction.

Card, Newell & Moran (1983)


MHP :: Perception

• MHP says: – Response time of perceptual

processor is proportional to intensity of stimulus

– Information is stored in memory according to the type of stimuli (e.g. acoustic, visual)

– Information ‘decays’ from working memory and may be stored in long term memory

• About 100msec • Measure by determining smallest

perceivable event (e.g. moving image on film)

Time to perceive an event e.g. perceive pattern of letter S


MHP :: Cognition

• MHP says:– Cognitive processor time

decreases with practice (Power Law of Practice)

– Cognitive processor time decreases with task load.

• About 70msec• Measured by ‘matching’

tests

Time to “connect inputs from the perceptual system to the right outputs of the motor system”

e.g. pattern S is equal to letter S

MHP :: Motor

• MHP says:– Time to move to a target

depends on distance and size of target (Fitts Law)

• About 70msec• Measured by

repetitive motor tasks

Time taken for ‘micro-movements’ to translate thought into patterns of voluntary movement

e.g. hit key that has S on it


MHP :: Principles

Fitts Law• Predicts time to move hand to target

given the distance and size of the target

Tpos = IM log2(2*Distance/Size)

– i.e: Time is longer the further the target is away and the smaller it is.

• Fitts law shown to match use of mouse well

• How about a user with motor impairments?


MHP :: Principles

Hick-Hyman Law • Predicts the “choice reaction time”

RT = a + b log2(number of choices)

– i.e. The more choices the longer it

takes to react.

• The reaction time to a choice depends on it’s likelihood – the more likely the option, the quicker the reaction


MHP :: Principles

Power Law of Practice • Predicts the effect of performing a

practiced task.Tn = T1n-

– i.e. Time decreases (exponentially) with practice


MHP :: Example

– TP – Perceptual Processor• Perceive the second symbol and store

in working memory visual store

– TC – Cognitive Processor• Tc * 1 Match symbol to previous (or

not)• Tc * 2 Decide to press YES or NO

– TM – Motor Processor• Process the signal to push the button

– Total: Tp + 2TC + Tm

User is shown a series of symbols – she has to press ‘YES’ when two identical symbols are shown in a row and ‘NO’ otherwise (I.e. a game of Snap!).


MHP for Assistive Technology

• Koester & Levine (1997):– Used a keystroke-level model to

model word prediction tasks.• Keystroke level model is a

Goals/Operators/Methods/Selection Rules (GOMS) model – similar to the MHP

• Validated the model for use for this task

• Successfully predicted prediction selection times

• John P Hansen – other use of GOMS model.


MHP for Assistive Technology

• Keates, Clarkson and Robinson (1998)– Measured the perceptual/cognitive/motor

times for range of able bodied and motor impaired users.

• Slower times for motor-processor (~50%)

• Slight variation in cognitive-processor• Completion of task (pressing key on

stimulus) did not conform to the MHP for motor-impaired users.

• Motor impaired users conformed to modified model with additional cognitive and perceptual processor cycles.

• No further research indicated…


MHP and Switch Access

• Applies to switching?– Many examples in Card et al. (1983)

refer to response to stimuli and selection from lists

• Some work and reference to MHP in Assistive Technology papers

• No extensive uptake of the model or any other models noted

• I propose that the investigation of the model with respect to switch access would provide valuable information.


Health Warning!

• I am not:– proposing models as a way of replacing

common sense– suggesting that a model will give us all the

answers about switching– saying that all users/clients will fit nicely

into a set of categories• Each person is different and the

environment and motivation is almost always the most important factor

• However, I believe that using HCI models for switch access can provide valuable information and provide a basis for developing an evidence base…


Modelling Examples

Switched Joystick VS P&G Mouse

• What is quicker? Using 3/4/5 switches as a directional joystick or a Joystick Mouse (e.g. P&G Joystick)– Some (AAC) devices are removing

ability to use more than 2 switches. The recommended replacement is to use a mouse device.

• Is this better or worse?


Modelling Examples

AutoScan VS Inverse Scan

• Anecdotally, most people use 1 switch AutoScan – why?– Inverse Scan is being dropped by AT

products as an option

• Is the cognitive load of AutoScan more or less that UserScan?


Research Areas

• Pre-requisit skills for switching• Validate the MHP for different

switching tasks • Evaluate the cognitive loads of

different components and methods of switching

• Monitor the effect of different methods of teaching on learning switching skills

• Investigate expert switch/device use• Effects of different conditions on the

components of the model• ………


Conclusions

• Used MHP as an example of a model that could be used with switch access

• EAT could build on the HCI field and apply a number of relevant models and theories

• Aim is to optimise switch access for users to enable them to be as effective as possible.


Other Relevant Work

• “Switch Access to Technology, a comprehensive Guide”. (Standards and reference manual for switch access)D Colven & S Judge, released shortly.

• Development of evidence base on Assistive Technology:

www.assistech.org.uk

• Open Source software for Assistive Technology:

www.oatsoft.org


References

• Citations:www.citeulike.org/user/simonjudge/

tag/switching

• Main HCI reference:Human Computer Interface; Card,

Newell & Moran (1983)

• Main AT-HCI reference:Use of Model Human Processor for

people with motor impairments; Keates, Clarkson and Robinson (1998)


[email protected]

http://www.sjinterface.co.uk/

ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction...

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