Week 3 Human-Technology Interface (HTI); Control Interfaces & Selection Methods

where does HTI fit?

it is embedded within the AT component of the HAAt model

HTI is how…

the person accesses, controls, and receives feedback from the device

HTI is the boundary where…

the user sends commands; through eye gaze, switch, movement, etc.

the technology provides feedback

what exchange determines whether an AT is usable?

the relationship between the user sending commands and the technology providing feedback

a perfectly selected device fails if…

the user cannot activate it reliably

the interface requires more endurance than the user has

feedback is not accessible to the user’s sensory abilities

HTI is often the difference between ______ and __________

access, abandonment

HAAT model connection to HTI is…

HTI is where all four components collide in real time

HAAT model components-

Human- motor, sensory, cognitive abilities

Activity- what the person wants or needs to do

Assistive Technology- hardware, software, and HTI

Context- physical, social, cultural, institutional environments

HTI describes…

how a person and a device communicate with each other

HTI includes:

how the user sends commands to the device

how the device provides feedback to the user

how efficiently, accurately, and reliably this exchange occurs

HTI is the ________ ________ between human ability and technological capability

functional bridge

two-way exchange at the HTI

user → technology (input) → technology (output) → user

in HTI the user is responsible for…

generating a reliable signal

control the timing, accuracy, and endurance of the signal

in HTI the device is responsible for…

confirm the action occurred

provide feedback in a sensory modality the user can access

provide visual, auditory, and/or tactile feedback

key points to remember about HTI…

it is not one thing

system of matched components involving- control site, selection method, control interface, feedback modality

Four elements of HTI

selection set- what choices exist

selection method- how choices are made

control interface- what the user physically operates

feedback modality- how the system responds

HTI; selection set:

the group of options available for the user to choose from

considers the size of the set, representation (symbol, text, etc.), and organization

a selection set that is too large, too small, or poorly organized can reduce _______ or _________

efficiency, accuracy

HTI; selection method:

how the user accesses items in the selection set

considers motor control and endurance, reaction time, and cognitive load and attention

direct selection-

user selects the desired item immediately

requires higher motor precision

indirect selection (scanning)-

options are presented sequentially

requires timing, attention, and sequencing

HTI; control interface:

the physical or biological means used to make selections

considers control site, required force, range, and precision, reliability and fatigue, and mounting and positioning

a control interface must match what the user can do _______ not what they can do once

consistently

HTI; feedback modality:

how the system communicates back to the user

considers sensory abilities, speed and clarity of feedback, environmental factors

without accessible feedback, the user cannot confirm _________ or ________ errors

success, correct

HTI: motor signal-

a purposeful, repeatable body-generated action used to control technology

HTI: control site-

the specific body part used to produce the motor signal

HTI: control interface-

the physical or digital device that captures the motor signal and translates it into control of technology

HTI: access-

the user’s ability to efficiently, accurately, and sustainably operate technology to perform an activity

to operate a control interface, the user must be able to generate a ________, _______ motor signal

consistent, usable

motor skills determine what _________ ______ are possible, which ___________ are realistic, and how long _________ can be sustained

control sites, interfaces, access

HTI: resolution-

how closely targets can be spaced and still be accurately selected

HTI: reliability-

ability to repeat the same movement consistently

HTI: versatility-

ability to perform different actions with the same control site

HTI decisions are based on functional ____________, not strength testing alone

motor performance

good HTI planning balances…

speed, accuracy, endurance, and future needs

why sensory skills matter-

for a technology interface to work, the user must be able to detect, interpret, and respond to feedback from the device

a perfect motor match with a device can fail if sensory feedback is…

inaccessible, delayed, or overwhelming

Key visual skills to consider:

visual acuity

tracking

peripheral vision

color sensitivity

HTI visual implications-

small icons may reduce accuracy even with good motor control

moving scan indicators require intact tracking

poor peripheral vision increases missed selections and fatigue

_______ and _______ targets improve peripheral visibility because they offer high contrast and are more easily detected in the peripheral visual field

blue, yellow

what color combination do you want to avoid on an AT device?

red/green for individuals with vision differences

HTI: auditory skills to consider-

ability to hear scanning prompts or selection cues

auditory processing speed and attention

tolerance to repetitive sounds

HTI: auditory implications-

auditory scanning can reduce visual demand

background noise may interfere with accuracy

headphones may improve performance but affect social participation

HTI: Tactile skills to consider-

ability to feel vibration, pressure, or resistance

sensory discrimination and tolerance

HTI: tactile implications-

vibration confirms successful activation

tactile feedback supports users with limited vision or hearing

overly strong feedback may be aversive or distracting

_______-sensory feedback is often best

multi

combining visual, auditory, and tactile feedback…

improves accuracy

reduces cognitive load

increases confidence and independence

sensory _______ helps users learn faster and catch mistakes because the same information is confirmed through more than one sensory system

redundancy

why does cognition matter in HTI?

AT requires the ability to attend, process, remember, decide, and correct actions in real time

many HTI failures may appear to be due to motor functions but are actually caused by…

cognitive overload

dwell selection-

an access method in which a user makes a selection by holding their cursor, pointer, or eye gaze on a target for a preset amount of time, rather than clicking or pressing a switch

scanning-

an access method in assistive technology in which choices are presented sequentially, and the user makes a selection by activating a switch or signal at the right time when the desired option is highlighted

longer messages-

messages that take many selections and sustained effort to create or complete

rate enhancement-

strategies built into AT technology systems to increase the speed and efficiency of communication or control, especially when access methods are slow

Strengths of the fingers/hands being the control site-

high precision and speed

highly versatile

familiar to users

limitations of using the fingers/hands as a control site-

fatigue, pain, tremor

progressive loss of function

strengths of using the head/chin as a control site-

good control when hands are limited

moderate precision

can support pointing or switch access

limitations of using the head/chin as a control site-

neck fatigue

requires stable head control

strengths of using the foot as a control site-

useful when upper extremities are unavailable

strong gross motor control

limitations of using the foot as a control site-

less precision

requires stable seating and positioning

strengths of using the eyes as a control site-

high resolution

minimal physical effort

effective when motor options are limited

limitations of using the eyes as a control site-

visual fatigue

lighting sensitivity

requires intact vision and attention

strengths of using the mouth as a control site-

reliable for users with high-level SCI

strong signal with minimal movement

limitations of using the mouth as a control site-

requires respiratory control

interferes with speech and eating

strengths of using the facial muscles as a control site-

small, isolated movements

useful when limb movement is limited

limitations of using the facial muscles as a control site-

difficult to isolate

fatigue and involuntary movements