The application of Human Computer Interaction principles to Electronic Assistive Technology

1. The application of Human Computer Interaction principles to Electronic Assistive Technology Simon Judge MEng, MIET Clinical Scientist Access to Communication and Technology, Birmingham, UK ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

2. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

3. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

4. 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. ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

5. 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) ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

6. 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” ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

7. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

8. HCI - EAT • HCI should, thus, obviously be heavily involved with EAT? • Lets use switch access as an example… ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

9. Input Bandwidth Switch Access 101 • Part of a spectrum/bandwidth of input • Using a single binary source to transmit information [ DEMO ] ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

10. 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) ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

11. Input Bandwidth 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? ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

12. 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) ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

13. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

14. 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) ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

15. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

16. MHP :: Cognition 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 says: • Cognitive processor time decreases with practice (Power Law of Practice) • Cognitive processor time decreases with task load. • About 70msec • Measured by ‘matching’ tests ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

17. MHP :: Motor Time taken for ‘micro-movements’ to translate thought into patterns of voluntary movement e.g. hit key that has S on it • MHP says: • Time to move to a target depends on distance and size of target (Fitts Law) • About 70msec • Measured by repetitive motor tasks

18. 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? ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

19. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

20. MHP :: Principles Power Law of Practice • Predicts the effect of performing a practiced task. Tn = T1n- • i.e. Time decreases (exponentially) with practice ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

21. 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!). ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

22. 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. ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

23. 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… ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

24. 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. ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

25. 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… ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

26. 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? ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

27. 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? ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

28. 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 • ……… ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

29. 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. ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

30. 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 ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

31. 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) ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology

32. www.SJinterface.co.uk Simon.judge@sbpct.nhs.uk ICCHP 2006 – Young Researchers – Simon Judge The application of Human Computer Interaction principles to Assistive Technology