Aphasia and speech/language assistive technology

6 min read · BoK 1BC· p. 16–17

Learning objectives (3)

Define aphasia and identify its most common causes
Describe augmentative and alternative communication (AAC)
Match AT solutions — text-to-speech, voice carryover, AAC — to specific communication needs

Why it matters

Language disorders — especially aphasia — affect millions of people after strokes and brain injuries. Unlike speech disorders, aphasia impairs the language system itself. The solutions it requires (AAC, simplified communication, relay services) are distinct from those for motor speech disorders. (BoK p. 16)

Aphasia

Aphasia is an acquired language disorder resulting from damage to the language areas of the brain — most often from stroke, but also from traumatic brain injury, brain tumors, or infections. It can affect any combination of:

Speaking (word-finding, sentence formation).
Understanding speech.
Reading.
Writing. (BoK p. 16)

Critically, aphasia does not affect intelligence. A person with severe aphasia may have intact memory, problem-solving ability, and emotional understanding — but be unable to communicate in conventional verbal or written language.

Aphasia varies greatly: some people speak fluently but with many errors; others speak only in single words or short phrases; others can read better than they can speak. The individual profile determines which AT is most useful.

Augmentative and alternative communication (AAC)

AAC refers to all methods — unaided and aided — that supplement or replace natural speech. (BoK p. 17)

Low-tech AAC

Communication boards display symbols, photographs, or written words that the user points to. They require no technology, are portable, and can be customized.
Alphabet boards allow spelling-based communication for users with literacy.

High-tech AAC

Speech-generating devices (SGDs) are dedicated devices that produce synthesized or digitized speech from symbols or text entry. They range from simple single-message devices to complex dynamic display systems.
AAC apps on tablets (Proloquo2Go, TouchChat) bring similar capability to commercial devices.

Text-to-speech and other AT

Text-to-speech (TTS) serves multiple populations:

As a reading support for people with aphasia, dyslexia, or low vision who struggle with text.
As a communication output for non-speaking users who type their message and have it spoken aloud.

Word prediction reduces the typing load for people whose aphasia or motor difficulties slow text entry. It presents likely next words after each keystroke.

Voice carryover is a telephone relay option for people who can speak but cannot hear (or cannot process audio): they use their own voice for the outgoing message and receive the other party’s speech as text. This serves people with deafness who retain speech, or hearing people with written communication needs. (BoK p. 17)

Real-world example

A 60-year-old executive has a stroke and develops Broca’s aphasia — she understands speech clearly but produces only short, effortful phrases. She uses a tablet-based AAC app that lets her select phrases and have them spoken aloud in meetings. Her organization installs a relay service option for phone calls. Within her home, she uses a communication board for quick, reliable exchanges with family.

Key terms

Aphasia: An acquired language disorder caused by brain damage, affecting the ability to speak, understand, read, or write, while intelligence remains intact. (BoK p. 16)
AAC (augmentative and alternative communication): Any method that supplements or replaces natural speech — ranging from communication boards to high-tech speech-generating devices. (BoK p. 17)
Text-to-speech (TTS): Software that converts written text to synthesized audio output, used both as AT output for users who cannot read and as communication for non-speaking users. (BoK p. 17)
Voice carryover: A relay service option in which a person who can speak but cannot hear uses their own voice and receives a text display of the other party's speech. (BoK p. 17)
Communication board: A low-tech AAC tool containing symbols, pictures, or words that a user points to in order to communicate. (BoK p. 17)
Word prediction: Software that suggests likely next words based on what has been typed, reducing keystroke load for users with language or motor difficulties. (BoK p. 17)

Check yourself

A 55-year-old who suffered a left-hemisphere stroke can understand everything said to her and has no muscle weakness. However, she can produce only short, telegraphic phrases ("want water," "go home") and struggles to find specific words. Her intelligence is clearly intact. Which condition does the BoK describe?

Aphasia — an acquired language disorder caused by brain damage
Dysarthria — a motor speech disorder caused by muscle weakness
Intellectual disability — a condition affecting cognitive functioning and adaptive behavior
Selective mutism — an anxiety-based condition

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a) Dysarthria — a motor speech disorder caused by muscle weakness
b) Selective mutism — an anxiety-based condition
c) Aphasia — an acquired language disorder caused by brain damage — correct answer
d) Intellectual disability — a condition affecting cognitive functioning and adaptive behavior

Explanation: Aphasia is an acquired language disorder caused by brain damage — the BoK cites stroke as the most common cause. It may affect speaking, listening, reading, or writing in any combination, but intelligence remains intact. The description of a post-stroke person who understands fully but can produce only short phrases is a classic aphasia profile (BoK p. 16).

An accessibility specialist is selecting an AAC solution for a person with severe aphasia who has limited literacy but intact fine motor control and can point accurately. Which AAC approach does the BoK identify as most appropriate for a user who can point but has limited reading ability?

a) Word prediction software
b) Alphabet board
c) Symbol-based communication board or speech-generating device — correct answer
d) Text-to-speech output using typed text

Explanation: The BoK identifies communication boards and SGDs using symbols or pictures as the AAC tools suitable for users who have limited literacy. Pointing to a symbol or photograph communicates meaning without reading or spelling. When selecting AAC, literacy level is a key variable — symbol-based tools serve users who cannot rely on text-based input (BoK p. 17).

A person with severe aphasia has intact hearing but cannot speak. She can type slowly using one hand. She needs to make telephone calls for daily business tasks. Which relay service option does the BoK identify as appropriate for someone who can hear the caller but cannot speak?

a) CART service
b) Induction loop
c) Voice carryover — correct answer
d) Text telephone (TTY)

Explanation: Voice carryover is the relay service designed for users who can hear but cannot produce intelligible speech. The relay agent types what the other party says (which the hearing user reads or hears), and types the user's typed responses back as speech. The BoK identifies it alongside AAC as a communication solution for non-speaking users with intact hearing (BoK p. 17).

Sources

BoK references

Section 1BC — IAAP CPACC Body of Knowledge v4.0 (Oct 2023), p. 16–17