How what you consider 'old age' changes when you turn 30, 40, 50, and 60

• As people get older, the way they think about age changes dramatically.
• Research points to the fact that we're naturally biased against age, but as we get older, that bias starts going away.
• "People also often feel younger than their actual age," UCLA psychologist Alan Castel told Business Insider. "At certain 'landmark' birthdays (30, 40, 50) research has shown that people will re-evaluate their age and take on/change habits."
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Aging is, of course, a constant in life, but as of late, it's also been a trending topic.

Earlier this month, FaceApp's old age filter went viral with snaps from celebrities like Gordon Ramsay and Drake. The controversial photo editing app has since been criticized for collecting and storing users' data, but apart from privacy concerns, the app has the uncanny ability to show how you'll look decades from now using artificial intelligence - throwing a surreal new light on old age.

The reporter writing this, for example, tried FaceApp's old age filter, and found it frightening, uncanny, and probably accurate. And, clearly, he's not the only one.

"People tend not to think about old age until they notice physical changes," says Alan Castel, psychology professor at UCLA and author of "Better With Age." Or, as the app's virality has attested, they see simulated changes.

"People also often feel younger than their actual age," he tells Business Insider. "At certain 'landmark' birthdays (30, 40, 50) research has shown that people will re-evaluate their age and take on/change habits." Their ideal age, or how old they wish they could be again, also tends to go up.

"Landmark" birthdays shift age perceptions.

For example, a 2018 study (with over 500,000 respondents!) found that landmark birthdays lead to all sorts of shifts, as in:

• By age 30, people's ideal age was their mid-20s. 30-year-olds felt their own age, and hoped to live to 89, on average.
• By age 40, the ideal age rose to 30. The age they felt like hovered around their late 30s, and they hoped to live to 88.
• By age 50, people's ideal age had gone up to their late 30s. 50-year-olds felt like they were 40. The age people hoped to live to dramatically increased after age 40, so 50-year-olds hoped to live to 89, just like the 30-year-olds.

The study, published in Frontiers in Psychology, noted that when adults were asked about their ideal age, older adults chose older ideal ages. For example, 30-year-olds, on average, chose their mid-20s as their ideal age range, while 60-year-olds chose their early 40s. 90-year-olds went further still by choosing 60 as their age of choice.

The way the U.S. prizes youth shifts these perceptions.

"Especially in American culture, there is a fascination with being and being perceived as young." William Chopik, a social-personality psychologist and Michigan State professor who worked on the study, told Business Insider. "We associate youth with good things." (So did the Ancient Greeks.)

Other research points to the negatives attitudes associated with aging. According to one 2016 study, people who are frowning looker older than people who aren't. "This only gets worse as people age - when you ask people how old they feel, they say they are younger and younger than they are in an effort to appear younger," Chopik said.

While it's unclear whether people actually feel younger than their age, or just say they do, Chopik thinks we're naturally biased to favor youth. In his study, the one with half a million respondents, Chopik asked participants when older age starts. The older the participant, the older the supposed start of old age usually was.

Chopik says people delay old age in an effort to appear younger. "It's possible that their attitudes become more negative (because they are confronted by their own aging), but at least we know that people push off older age into the future when this realization (that they're getting old) starts to creep in," he says.