Premed · Premed · Introductory Psychology
Lecture 14: Language and Intelligence
Introductory Psychology
Learning Objectives
By the end of this lecture, students will be able to:
- Describe the structure of language and the stages of language development
- Evaluate the theories of language acquisition (nativist, learning, interactionist)
- Discuss the relationship between language and thought (linguistic relativity)
- Define intelligence and compare the major theories of intelligence
- Evaluate the use and misuse of intelligence tests, including issues of reliability, validity, and bias
Lecture Content
I. The Structure of Language
Language is a system of symbols and rules for combining them to communicate meaning. It possesses several remarkable properties: it is generative, allowing an infinite number of sentences to be created from a finite set of elements; it is structured, governed by grammatical rules; it is referential, capable of representing objects, events, ideas, and relationships; and it exhibits displacement, meaning it can refer to things not present in the immediate environment.
Language is organized at multiple structural levels. Phonemes are the smallest units of sound that distinguish meaning — there are roughly 40 in English, and the difference between /b/ and /p/ is what distinguishes "bat" from "pat." Morphemes are the smallest units of meaning, including whole words and affixes; the word "unhappiness" contains three morphemes (un + happy + ness). Syntax refers to the rules for combining words into grammatical sentences, while semantics concerns the meaning of words and sentences. Pragmatics governs the social rules for using language in context, including tone, indirectness, and turn-taking.
II. Language Development
Language acquisition follows a remarkably consistent sequence across all cultures. In the first four months, infants produce cooing sounds — vowel-like vocalizations. Between four and six months, babbling begins, consisting of repetitive consonant-vowel combinations such as "ba-ba" and "da-da." Importantly, early babbling includes sounds from all of the world's languages, but by around 10 months, it narrows to include only sounds present in the infant's native language. Deaf infants exposed to sign language babble with their hands, demonstrating that the babbling impulse is fundamentally linguistic rather than merely vocal.
First words appear around 12 months, usually consisting of nouns ("mama," "dada," "ball"). Children at this stage may overextend words — calling all four-legged animals "doggy" — or underextend them, using "car" only for the family car. Between 18 and 24 months, vocabulary expands rapidly and children begin producing two-word telegraphic speech such as "want milk" and "daddy go." By age two to three, grammar is acquired at an astonishing pace, and children produce overregularization errors — saying "goed" instead of "went" or "foots" instead of "feet" — which paradoxically demonstrate that they are applying grammatical rules rather than simply imitating what they hear. By age five to six, most basic grammar has been mastered, though vocabulary and pragmatic skills continue to develop.
A critical (or sensitive) period for language acquisition exists before puberty, after which language learning becomes substantially more difficult. The tragic case of Genie, an isolated child discovered at age 13, provides evidence: she never achieved full grammatical competence despite years of intervention. Research by Newport (1990) showed that age of immigration is a strong predictor of grammatical proficiency in a second language, with earlier exposure leading to more native-like performance.
III. Theories of Language Acquisition
The behaviorist approach, associated with Skinner, holds that language is learned through operant conditioning — parents reinforce correct speech and correct errors, and children learn through shaping and imitation. This account has been widely criticized because it cannot explain the speed, creativity, and universality of language acquisition; children routinely produce sentences they have never heard before.
Chomsky's nativist theory proposes that humans are born with an innate language acquisition device (LAD) — a biological predisposition to learn language — and that all languages share an underlying universal grammar. Evidence for this view includes the universal developmental sequence, the existence of a critical period, and the poverty of the stimulus (children learn far more than the input alone can explain). Critics argue that the theory does not fully specify the LAD and underestimates the role of social interaction.
Interactionist theories take a middle path, proposing that language emerges from the interplay of biological readiness, cognitive development, and social experience. The social pragmatic approach emphasizes that children learn language through joint attention, social cues, and communicative intent. Usage-based theory holds that children extract linguistic patterns from the language they hear through statistical learning.
IV. Language and Thought
The relationship between language and thought has been debated for decades. Linguistic determinism — the strong version of the Sapir-Whorf hypothesis — claims that language determines thought, making it impossible to think about things for which one's language has no words. This position has been largely rejected; people clearly can think about concepts without having specific words for them. The weaker version, linguistic relativity, holds that language influences thought and perception. Research supports this more modest claim: languages with more color terms facilitate faster discrimination among those colors; languages differ in how they encode spatial relations; and Mandarin speakers may conceptualize time differently than English speakers, using vertical rather than horizontal metaphors. The effect is real but modest — language shapes but does not determine thought.
Much of our thinking is nonverbal, including mental imagery, spatial reasoning, musical cognition, and emotional experience. Bilingualism has attracted considerable research interest, with some evidence (though debated) suggesting advantages in executive function, attentional control, and cognitive flexibility. There is no evidence that bilingualism causes language delay or confusion in children, and bilingual individuals may experience reduced cognitive decline in old age.
<image>A timeline of language development from birth to age 6. Panel A: Birth to 4 months — cooing sounds with a baby icon. Panel B: 4-10 months — babbling with speech bubbles showing "ba-ba, da-da." Panel C: 12 months — first words with a toddler pointing at a dog and saying "doggy." Panel D: 18-24 months — telegraphic speech with speech bubble "want milk." Panel E: 2-3 years — overregularization with speech bubble "I goed to the park." Panel F: 5-6 years — complex sentences. Below the timeline, a bar chart shows vocabulary size expanding exponentially from about 1 word at 12 months to several thousand by age 6.</image>
V. Intelligence: Definitions and Theories
Intelligence is broadly defined as the ability to learn from experience, solve problems, and use knowledge to adapt to new situations. Psychologists have proposed several models of its structure. Charles Spearman argued for a general intelligence factor (g) that underlies performance on all cognitive tasks, supported by the observation that scores on diverse mental tests tend to be positively correlated. Specific abilities (s factors) also contribute to performance on individual tasks. Louis Thurstone disagreed, identifying seven primary mental abilities — verbal comprehension, word fluency, number facility, spatial visualization, associative memory, perceptual speed, and reasoning — and rejecting the idea of a single g factor.
Howard Gardner's theory of multiple intelligences proposes eight independent types of intelligence: linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalistic. While appealing, this theory has drawn criticism for weak empirical support for the independence of these intelligences and for potentially conflating talent with intelligence. Robert Sternberg's triarchic theory distinguishes among analytical intelligence (traditional academic problem-solving), creative intelligence (generating novel ideas and adapting to new situations), and practical intelligence (everyday problem-solving or "street smarts"). Emotional intelligence, conceptualized by Salovey and Mayer and popularized by Goleman, refers to the ability to perceive, understand, manage, and use emotions effectively. It predicts social success and well-being, though its distinctness from personality traits remains debated.
VI. Intelligence Testing
Alfred Binet developed the first intelligence test in 1905 to identify children who needed extra help in French schools, measuring mental age — the level of cognitive performance typical of children at a given chronological age. Lewis Terman adapted Binet's test for American use as the Stanford-Binet, introducing the intelligence quotient calculated as IQ = (mental age / chronological age) x 100, though this ratio IQ is no longer used for adults.
David Wechsler developed the most widely used modern intelligence tests (WAIS for adults, WISC for children, WPPSI for young children), which use deviation IQ — scoring based on comparison to same-age peers — with a mean of 100 and a standard deviation of 15. Subtests assess verbal comprehension, perceptual reasoning, working memory, and processing speed. IQ scores follow a normal distribution: approximately 68% of people score between 85 and 115, and about 95% score between 70 and 130. Intellectual disability is typically defined as an IQ below 70 accompanied by deficits in adaptive functioning, while giftedness is commonly defined as an IQ above 130.
Good tests must demonstrate reliability (consistency of scores, with IQ tests typically achieving correlations of 0.90 or higher), validity (actually measuring what they claim to measure), and standardization (uniform procedures and norms based on representative samples). IQ moderately predicts academic achievement, job performance, income, and health outcomes. The Flynn effect — the finding that average IQ scores have risen by roughly 3 points per decade over the 20th century — may reflect improvements in nutrition, education, healthcare, and environmental stimulation.
VII. The Nature-Nurture Debate in Intelligence
Twin studies show that identical twins reared apart have IQ correlations of approximately 0.70-0.75, and heritability estimates for intelligence range from 50% to 80% of the variation in studied populations. Heritability increases with age as genetic influences become more prominent. Crucially, however, high heritability does not mean intelligence is fixed, nor can within-group heritability be used to explain between-group differences.
Environmental influences are substantial. Adoption studies show that adopted children's IQs correlate with both biological and adoptive parents. Poverty, malnutrition, lead exposure, and lack of stimulation all reduce IQ scores, while education and enrichment programs such as Head Start can boost cognitive abilities. Stereotype threat, demonstrated by Steele and Aronson, shows that awareness of negative stereotypes about one's group can impair test performance, adding a situational dimension to the testing picture.
Mean differences in IQ scores between racial and ethnic groups in the United States are best explained by socioeconomic, educational, and environmental factors — not by genetic differences between groups. Within-group heritability provides no evidence about the causes of between-group differences.
<image>A bell curve diagram of the normal distribution of IQ scores. The x-axis shows IQ scores from 55 to 145, and the y-axis shows the percentage of the population. The curve is divided into standard deviation segments: 68% fall between 85-115 (one SD), 95% between 70-130 (two SDs), 99.7% between 55-145 (three SDs). Labels indicate: "Intellectual disability" below 70, "Low average" 80-90, "Average" 90-110, "High average" 110-120, "Superior" 120-130, "Gifted" above 130. A sidebar compares the major theories of intelligence: Spearman's g, Thurstone's primary abilities, Gardner's multiple intelligences, and Sternberg's triarchic theory.</image>
