Capstone: Development Across the Life Span

This is Unit Eighteen, the capstone, part two, the last lecture of the course, on perception and intelligence across the lifespan. Part one closed on language as readiness meeting a social world. Part two runs the capstone's last two threads. Carry one question through this part: how much of perception and intelligence is fixed, and how much is shaped by experience and time? For perception, the answer comes at the entry that asks whether it is built in or built up. For intelligence, it comes at the course's final entry, which asks whether intelligence declines with age. By the end you will be able to say which sense is most and least developed at birth. To match late-life vision symptoms to their diseases. To explain how the visual cliff was reinterpreted. To name three theories of intelligence, and say why learning styles are a misconception. And to explain why intelligence does not decline across the board.

Six entries on the senses from birth: what newborns sense, how researchers can tell, and how perception grows with movement.

Sensation, and perception.

HGD 2571 Sensation and Perception

Perceptual development begins with a distinction from unit three: sensation is detecting a stimulus through the senses; perception is interpreting it, as a newborn hears a voice and turns toward it as familiar. Perceptual change runs across the whole lifespan, from the newborn's first weeks to late-life hearing loss.

The newborn's senses.

HGD 2572 The Newborn's Senses

The senses are unevenly developed at birth. Vision is the least developed: blurry, best at close range, with low acuity, though basic colour vision is present and nearly adult by four to six months. Hearing works at birth, and newborns prefer speech and their native language. Touch is the most highly developed sense, and taste and smell begin before birth. A newborn turns toward her mother's voice and calms at her touch while barely focusing on her face. Exam items ask which sense is most or least developed at birth: touch the most, vision the least.

Depth, and the visual cliff.

HGD 2573 Depth and the Visual Cliff

Depth perception is absent at birth and begins around two months, and on Gibson and Walk's visual cliff, few crawling infants crossed the deep side; a new walker stops at the edge where an experienced crawler edged on. The misconception is that the cliff proves an inborn fear of heights; avoidance grows with experience of moving.

Habituation, and preference.

HGD 2574 Habituation and Preference

Researchers read infants' perception through habituation, a decreasing response to a repeated stimulus, and through looking-time preferences, as infants look longer at faces than patterns and at curved lines than straight. These methods let researchers ask what infants perceive before they can speak.

Senses together, and a sensitive period.

HGD 2575 Intermodal Perception and a Sensitive Period

Intermodal perception is awareness through several senses at once, as an infant links the sound of a voice with the moving lips that make it. The visual cortex develops in a burst at two to four months, a sensitive period for vision, and most visual areas are developed by twelve months.

Perception, and action.

HGD 2576 Perception and Action

Dynamic systems theory holds that motor milestones emerge from interacting systems, body, senses, brain and environment, and the visual cliff shows perception tuned by moving, as Karen Adolph's infants learn how to move safely with each new way of moving. Perception and action develop together.

Three entries on the senses in adulthood, from reading glasses to hearing and dementia.

The senses at midlife.

HGD 2577 Midlife Senses

Perceptual change resumes in midlife: presbyopia blurs near vision and presbycusis takes high frequencies first, like a forty-six-year-old holding a menu at arm's length in a noisy restaurant, while proprioception declines, raising fall risk. Midlife sensory change is gradual and varies widely between people.

Vision and hearing in late life.

HGD 2578 Vision and Hearing in Late Life

Late adulthood adds three serious eye diseases. Cataracts cloud the lens and are treatable by outpatient surgery. Age-related macular degeneration damages the centre of the retina, removing central vision. Glaucoma, usually from raised eye pressure damaging the optic nerve, takes peripheral vision first. Presbycusis, age-related hearing decline, begins with high-pitched tones, and lifelong noise exposure is a major predictor. The misconception is that presbycusis means everything sounds quieter. Exam items describe a symptom: cloudiness points to cataracts, lost central vision to macular degeneration, tunnel vision to glaucoma, near-focus trouble to presbyopia.

Hearing, cognition, and dementia.

HGD 2579 Hearing, Cognition and Dementia

Hearing loss is the largest single modifiable dementia risk factor in Livingston's estimates, but a hearing-aid trial found no overall cognitive benefit, and only about sixteen percent of adults twenty to sixty-nine who could benefit from hearing aids have ever used them. Whether hearing loss causes dementia or signals it remains unresolved.

One entry that weighs perception's nature and nurture. The first half of the opening question is answered here.

The first payoff: built in, or built up?

HGD 2580 Perception: Built In or Built Up?

The perceptual arc returns to nature and nurture, and it answers the first half of this part's question. Some capacities are present at birth: newborns hear and prefer their native language, and touch is well developed. Others are built by experience and timing. The visual cortex develops in a burst at two to four months, a sensitive period. The visual cliff, once read as proof of an innate fear of heights, turned out to reflect locomotor experience. Tasks that do not require reaching reveal infant abilities earlier than Piaget thought, so what infants seem to lack can depend on how they are tested. And at the other end of life, hearing loss is linked to dementia, but a trial of hearing aids found no overall benefit, so an association is not a cause. The misconception is that perception is either innate or learned; the evidence shows both.

Four entries on what intelligence is: its genetic range, one ability or several, and a misconception.

Genes, environment, and reaction range.

HGD 2581 Genes, Environment and Reaction Range

The intelligence arc begins with reaction range: genes set limits, and environment decides where within them a person lands. Twin and adoption studies show genetic influence, while lead exposure lowers intelligence and stimulating experiences support it. No single intelligence gene exists; heritability describes variation across a population.

What intelligence is.

HGD 2582 What Intelligence Is

Intelligence is broadly the ability to adapt to the world, in Sternberg's description, and Spearman proposed a general ability, g, underlying performance across tasks, after Binet and Simon saw children who did well on one task do well on others. Whether intelligence is one ability or several is the question that follows.

Theories of intelligence.

HGD 2583 Theories of Intelligence

Unit seven taught three answers to whether intelligence is one thing or many. Cattell divided general ability into fluid intelligence, logic and novel problem-solving, and crystallized intelligence, accumulated knowledge. Gardner proposed eight intelligences, from linguistic and logical-mathematical to interpersonal, intrapersonal and naturalistic. Sternberg proposed analytical, creative and practical intelligence, and practical intelligence grows with experience. Gardner's theory is contested: critics call the intelligences talents and note overlap. Standard tests measure mainly analytical intelligence. Exam items describe a task and ask which ability or theory it fits.

Learning styles, the misconception.

HGD 2584 Learning Styles, the Misconception

Learning styles is the idea that people learn best through a preferred mode, and the meshing hypothesis, matching instruction to style, lacks evidence: a questionnaire may label a student a visual learner, but no experiment shows matched teaching helps. Multiple intelligences are not learning styles; Gardner describes abilities, not preferred ways of receiving instruction.

Three entries on measuring intelligence: how scores work, the two ends of the scale, and culture.

How intelligence is measured.

HGD 2585 Measuring Intelligence

Intelligence testing grew from ratio IQ, mental age divided by chronological age, times one hundred, to modern deviation IQ, a score's distance from one's age-group norm. Tests are normed to a mean of one hundred and a standard deviation of fifteen, so about sixty-eight percent of people score between eighty-five and one hundred fifteen. Scores rose about three points per decade in the Flynn effect, and tests serve screening, prediction and diagnosis. The misconception is that modern IQ is still mental age over real age. A score is one piece of the picture, and a good test needs reliability and validity.

The two ends of the scale.

HGD 2586 The Extremes: Disability and Giftedness

Intellectual disability requires limits in both intellectual functioning and adaptive behaviour, and a low score alone does not establish it; about two percent score above one hundred thirty, one marker of giftedness. A gifted nine-year-old may thrive after skipping a grade, and acceleration has not generally shown negative social outcomes.

Culture, and testing.

HGD 2587 Culture and Testing

Intelligence tests are criticized for cultural bias, and cultures differ in what they count as intelligence, from analytical ability to its interpersonal uses. Nonverbal, culture-fair tests such as Raven's matrices still need cultural adaptation. A test measures intelligence as its designers defined it, which is why cultural critiques persist.

Three entries to close the capstone and the course, on intelligence across adulthood. The second half of the opening question is answered at the last of them.

Two abilities across adulthood.

HGD 2588 Fluid and Crystallized Across Adulthood

Cattell's two abilities follow different paths: fluid intelligence peaks in the twenties, while crystallized intelligence keeps rising through midlife and holds past sixty, like a fifty-five-year-old editor who knows more words than ever but learns new software more slowly. The two change together within individuals rather than compensating.

Wisdom, and expertise.

HGD 2589 Wisdom and Expertise

Wisdom, expert knowledge of life's pragmatics, is predicted only marginally by age, and expertise comes from deliberate practice and experience, like an older chess expert who considers fewer moves yet chooses better ones. The misconception is that wisdom comes automatically with age; openness and learning from experience matter more.

The last entry: does intelligence decline with age?

HGD 2590 Does Intelligence Decline With Age?

The last arc ends on a question the exam often asks. Cross-sectional studies once suggested steep intellectual decline with age, but they confused age with cohort. The Seattle Longitudinal Study, following the same people since nineteen fifty-six, found verbal memory, spatial skills, inductive reasoning and vocabulary rising into the seventies, while numerical computation and perceptual speed declined. Fluid intelligence falls in late life and crystallized intelligence holds or rises, the two changing together. Practice and education raise the level a person reaches, some decline may reflect disuse, and training helps trained skills, though whether brain games prevent dementia remains inconclusive. That answers the second half of this part's question. The misconception is that intelligence declines across the board. Some abilities decline, some hold and some grow. Age brings losses and gains together, and the balance differs from person to person.

Look at what you can now do. You can say that touch is the most developed sense at birth and vision the least. You can match late-life symptoms: cloudiness to cataracts, lost central vision to macular degeneration, tunnel vision to glaucoma. You can explain the visual cliff's reinterpretation: avoidance grows with experience of moving, not from an inborn fear. You can name Cattell's, Gardner's and Sternberg's theories, and say that matching teaching to learning styles lacks evidence. And you can explain that intelligence brings losses and gains together: some abilities decline, some hold, and some grow. That closes the capstone, and the course.