Key Concepts of Language Disorders

Why This Matters

Language disorders sit at the intersection of some of psychology's most important domains: brain localization, developmental psychology, learning processes, and social behavior. When you study these disorders, you're not just memorizing symptoms—you're learning how damage to specific brain regions produces predictable deficits, how developmental timelines affect language acquisition, and how communication difficulties ripple outward into anxiety, social isolation, and academic struggles. The AP exam loves to test your understanding of brain-behavior relationships, particularly through aphasia questions that ask you to connect lesion location to specific symptoms.

Don't approach this list as ten separate disorders to memorize. Instead, focus on the underlying mechanisms: acquired vs. developmental onset, expressive vs. receptive deficits, neurological vs. psychological causes. When you understand why Broca's aphasia produces halting speech while Wernicke's aphasia produces fluent nonsense, you can reason through any question the exam throws at you. Know what concept each disorder illustrates, and you'll be ready for both multiple choice and FRQ applications.

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Acquired Language Disorders: When Brain Damage Disrupts Communication

These disorders result from injury to a previously healthy brain, typically from stroke, trauma, or disease. The specific symptoms depend on which brain region is damaged, making these disorders powerful evidence for localization of function—a concept the AP exam tests repeatedly.

Aphasia

• Language impairment caused by brain damage—most commonly from stroke affecting the left hemisphere, where language centers are typically located
• Affects multiple modalities including speaking, comprehension, reading, and writing, with specific deficits depending on lesion location
• Key exam concept: demonstrates that language is not a single ability but a collection of processes housed in different brain regions

Broca's Aphasia

• Non-fluent, effortful speech with intact comprehension—patients understand what's said to them but struggle to produce words
• Damage to Broca's area in the left frontal lobe disrupts speech production and grammar while leaving meaning intact
• Characteristic "telegraphic speech" with short, fragmented sentences lacking function words ("Want... coffee... now")

Wernicke's Aphasia

• Fluent but meaningless speech with impaired comprehension—patients speak easily but produce word salad or nonsense
• Damage to Wernicke's area in the left temporal lobe disrupts language comprehension and meaningful word selection
• Patients often unaware of their deficit because they cannot monitor their own speech for errors—a striking contrast to Broca's patients

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Developmental Language Disorders: When Acquisition Goes Differently

These disorders emerge during childhood development rather than from injury to a mature brain. The underlying causes involve atypical neural development or genetic factors, and early intervention is critical because the brain's plasticity decreases with age.

Specific Language Impairment (SLI)

• Language difficulties without an identifiable cause—no hearing loss, intellectual disability, or neurological damage explains the deficit
• Affects grammar and vocabulary acquisition while other cognitive abilities develop normally, suggesting language-specific neural systems
• Important distinction: demonstrates that language can be selectively impaired, supporting modularity theories of cognition

Developmental Language Disorder (DLD)

• Significant difficulties with both expressive and receptive language that persist beyond typical developmental delays
• Impacts academic success and social relationships because language underlies reading comprehension, classroom participation, and peer interaction
• Not outgrown without intervention—distinguishes DLD from simple late talking, which typically resolves naturally

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Reading and Writing Disorders: When Written Language Is Affected

These learning disabilities specifically target the processing of written language. They involve difficulties with the visual-phonological connections required for decoding text or the motor-cognitive coordination needed for writing.

Dyslexia

• Difficulty with reading despite normal intelligence and instruction—the most common learning disability, affecting approximately 5-10% of the population
• Core deficit in phonological processing—trouble connecting letters to sounds, which disrupts decoding and spelling
• Not a vision problem—a persistent misconception; dyslexia involves language processing in the brain, not how eyes perceive text

Dysgraphia

• Impaired writing ability affecting handwriting legibility, spelling, and organizing thoughts on paper
• May involve fine motor difficulties that make the physical act of writing laborious, or cognitive difficulties with translating ideas into written form
• Often co-occurs with dyslexia because both involve language processing, though dysgraphia specifically targets output rather than input

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Speech Fluency and Social Communication Disorders

These disorders affect how smoothly speech flows or how effectively individuals navigate social communication contexts. The underlying mechanisms range from motor control issues to anxiety to broader neurodevelopmental differences.

Stuttering

• Disrupted speech fluency characterized by repetitions, prolongations, or blocks that interrupt the natural flow of speaking
• Often accompanied by secondary behaviors—physical tension, avoidance of certain words, or anxiety about speaking situations
• Neurological and psychological components interact; brain imaging shows differences in speech motor areas, while stress typically worsens symptoms

Selective Mutism

• Consistent failure to speak in specific social situations despite speaking normally in other contexts (typically at home)
• Classified as an anxiety disorder, not a language disorder—the child has intact language abilities but anxiety prevents speech in certain settings
• Often misinterpreted as defiance or shyness when it actually reflects intense social anxiety requiring specialized behavioral intervention

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Neurodevelopmental Disorders Affecting Communication

These broader developmental conditions include communication difficulties as one component of a larger syndrome. Language impairments in these disorders reflect differences in how the brain processes social and communicative information.

Autism Spectrum Disorder (ASD)

• Communication difficulties embedded within broader social and behavioral differences—not a pure language disorder but significantly impacts language development
• Variable language presentation ranging from nonverbal to highly verbal with atypical features like echolalia, pronoun reversal, or overly formal speech
• Pragmatic language particularly affected—understanding sarcasm, reading social cues, and adjusting communication style to context prove challenging even for verbally fluent individuals

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Quick Reference Table

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Self-Check Questions

1. Both Broca's aphasia and Wernicke's aphasia result from left hemisphere damage. What specific difference in lesion location explains why one produces non-fluent speech while the other produces fluent but meaningless speech?

2. A child speaks fluently at home but has never spoken a word at school despite two years of attendance. Which disorder does this describe, and why is it classified as an anxiety disorder rather than a language disorder?

3. Compare and contrast dyslexia and dysgraphia: What do they share as specific learning disabilities, and how do their core deficits differ in terms of language input versus output?

4. If an FRQ asks you to explain how brain damage can produce different language deficits depending on location, which two disorders provide the strongest contrasting examples, and what would you emphasize about each?

5. A student has significant vocabulary and grammar difficulties but scores normally on nonverbal IQ tests and has no hearing impairment. Which developmental language disorder does this pattern suggest, and what does it reveal about the modularity of language in the brain?