Birthday-card quips about the supposed horrors of getting older. “If ever there were a time to laugh and celebrate and dance the night away, it was about 20 years ago!”

Flashes of forgetfulness laughed off as “senior moments.”

Intended compliments like “You look great for your age!”

Products, advertising and magazine articles that promise to “erase signs of aging.”

Are these familiar clichés nothing more than harmless teasing, good-natured joking, genuine flattery and helpful advice?

Not necessarily. To academics and advocates who study negative stereotypes surrounding old age, they're examples of ageism.

Of course, casual remarks are not illegal, unlike age-based employment discrimination. Labor statistics show that older job-seekers have more difficulty getting hired — which is why they are frequently advised to color their hair, update their wardrobes and lop the earliest jobs off their résumés.

Casual ageism, on the other hand, isn't even especially frowned upon. It's so common it may seem routine, trivial, well-intentioned. But it's not necessarily harmless. Researchers have found numerous links between cultural ageism and health problems — physical, cognitive and emotional — among older people.

“There can be no movement unless the public clearly understands many of the powerful aspects of ageism,” said Margaret Gullette, a resident scholar in women's studies at Brandeis University and author of the just-published “Ending Ageism, or How Not to Shoot Old People.”

“People don't even know how to deal with ageism, so they don't recognize it when it happens to them. They don't know how to complain about it.”

Challenging ageism means getting people to pay closer attention to messages they've been hearing all their lives.

NEGATIVE IMAGES

Those messages are found in jokes and insults and compliments and offhand remarks. They're in the TV programs and commercials we watch (one study found that people who watched more TV held more anti-age biases). They're posted on Facebook, which officially bans hate speech based on categories including race, nationality, religion and gender — but not age. They're in the advertising claims that have built a $200 billion “anti-aging” industry of skin creams, Botox injections, hair coloring, hair restoration and cosmetic surgery.

From childhood on, Americans receive messages that old age means “you're unhealthy, your mind is shot, you're boring, you're depressed and sad and lonely,” said Sally Brown of St. Paul, who teaches a course called “Aging With Gusto” through the St. Paul-based Vital Aging Network.

True, some older people are unhealthy or lonely — as are some young people. But similar characteristics are interpreted differently by age. A physically fit young person is healthy; a fit old person seems “younger.” A teenager losing the car keys is momentarily careless, an older person is developing dementia.

Brown, who is 71, has been alert to cultural ageism for decades. She joined the anti-ageist Gray Panthers at age 36; after meeting some local members of the activist group, she decided they were “really cool people who were living their values.” (She eventually served as the chairman of the Panthers' national board and as volunteer executive director.)

“You see this 'other' category of people,” Brown said. “It happens when you're younger and people are telling you about what old means and you're incorporating it. Assuming you live a while and become old, you turn it against yourself and it gets internalized.”

Statements that denigrate older people's functioning, thinking and appearance, advocates say, can lead to old people being stigmatized, isolated, ignored, politically disadvantaged and treated as “others.”

Yet despite — or because of — the ubiquity of these messages, people rarely consider that they might be damaging. Compared with other common prejudices, ageism is rarely discussed.

“Ageism is a thing, just like racism and sexism, and it's been under the radar for, well, forever,” said Todd Nelson, a psychologist at California State University. While researching the psychology of prejudice in general, Nelson noticed the scarcity of information about ageism. So he published a book: “Ageism: Stereotyping and Prejudice Against Older Persons.”

“In my writing, I ask the very simple question: Why are we hiding that we're getting older?” Nelson said. “It implies we're ashamed of getting older, that it's bad to get older. It's so deeply embedded in our culture.”

Biases take different forms with different targets, so comparisons aren't always valid, but sometimes swapping groups in a statement can highlight offensiveness.

A birthday card that says “'Ha ha ha, too bad you're Jewish,'” Nelson said, “wouldn't go over so well.”