"The children now love luxury; they have bad manners, contempt for authority; they show disrespect for elders and love chatter in place of exercise," Greek philosopher Socrates onced bitched (it's not recorded whether he was standing on his lawn shaking his fist).

Despite the passing of more than 2,000 years his complaint sounds exactly like some modern oldster opining about the many faults of Millennials (including here on Inc.com).  

In short, older folks have always lamented the sorry state of 'kids these days,' leaving behind a shockingly long and repetitive record of complaints. Which is kind of hilarious, but also perplexing. What is it exactly about middle age that seems to make people suddenly think the next generation is horrible compared to their own youthful foibles? 

You might suspect it's just that getting old makes you grumpy. And science shows it's true that the grind of midlife does tend to cause a dip in happiness. But according to a fascinating new study out of the University of California, Santa Barbara highlighted in Discover Magazine, there's another, more surprising reason we so often fall into complaining about 'kids these days.'

You're terrible at remembering yourself at 18. 

The researchers kicked off their research the way you'd expect. They asked a random selection of adults to rate the intelligence, respect, and reading habits of today's youth. It's no surprise that respondents had about as positive things to say as Socrates. The kids are snotty and ill informed, the cantankerous adults claimed. 

So far, so expected. But then the researchers did something clever. They also asked participants to rate themselves in these same traits. Were they big readers? Clever? Respectful of authority? When the researchers put the two sets of responses side by side a fascinating pattern emerged. The higher a person rated themselves on a particular measure, the lower they rated today's youth. 

"People that aren't very intelligent or aren't very well read or don't respect authority, they tend not to think kids are so bad," noted study co-author John Protzko. 

Why? "First, we tend to judge others more harshly in areas where we excel. An ardent reader, then, will be more likely to deride someone else's reading habits," explains Discover's Nathaniel Scharping. But second and more interestingly "our memories of what we were like as children can't always be trusted."

If you're a dedicated bookworm now, it's easy to forget that you barely cracked the assigned reading back in college. If you've learned over the decades to trust leaders, you might forget how rebellious you were back in the day.  People, in other words, tend to use their current level of ability as a yardstick, forgetting exactly how much development it took them to reach their adult form. 

"We are imposing our current self on the past," says Protzko. 

How not to become a grumpy old cliche

This subtle form of moving the goal posts, which causes us to judge young people by the same standards we judge far more experienced adults, is the root cause of our several thousand year history of bemoaning the horrible state of the youth.  

That's good news for young people who intuitively know their grumpy elders are amnesiac about the missteps and shortcomings of their own early years. You can now tell any adult who slags off your generation that they're suffering from memory problems, and science proves it. 

But the findings are also a useful reminder for those of us watching youth retreat in the rearview mirror. Our assessments of young people are almost certainly marred by our own faulty assessment of our own past character and abilities. Being aware of the bias might help us correct for it and avoid becoming the cliche of the grumpy oldster shaking her fist at "kids these days," and missing out on benefiting from the talent and insights of the young.