2 . Parents and kids today dress alike, listen to the same music, and are friends. Is this a good thing? Sometimes, when Mr Ballmer and his 16-year-old daughter, Elizabeth, listen to rock music together and talk about interests both enjoy, such as pop culture, he remembers his more distant relationship with his parents when he was a teenager.

“I would never have said to my mum, ‘Hey, the new Weezer album is really great.     1    ’” says Ballmer. “There was just a complete gap in taste.”

Music was not the only gulf. From clothing and hairstyles to activities and expectations, earlier generations of parents and children often appeared to move in separate orbits (轨道).

Today, the generation gap has not disappeared, but it is getting narrow in many families. Conversations on subjects such as sex and drugs would not have taken place a generation ago.     2     And parent-child activities, from shopping to sports, involve a feeling of trust and friendship that can continue into adulthood.

No wonder greetings cards today carry the message, “To my mother, my best friend.”

But family experts warn that the new equality can also result in less respect for parents. “There’s still a lot of strictness and authority on the part of parents out there.     3     In the middle of that change, there is a lot of confusion among parents,” says Kerrie, a psychology professor at Lebanon Valley College.

Family researchers offer a variety of reasons for these evolving roles and attitudes.     4     Great cultural changes led to more open communication and a more democratic process that encourages everyone to have a say.

“My parents were on the ‘before’ side of that change, but today’s parents were on the ‘after’ side,” explains Mr Ballmer. “It’s not something easily accomplished by parents these days, because life is more difficult to understand or deal with, but sharing interests does make it more fun to be a parent now.”

4 . AI could help us deconstruct the magic of music

We all know that music is a powerful influencer.     1     Fitness without a warm-blooded song would be boring. But is there a way to quantify these reactions? And if so, could they be reverse-engineered and put to use?

In a new paper, researchers at the University of Southern California mapped out how things like tone, rhythm, and harmony cause different types of brain activity, physiological reactions (heat, sweat, and changes in electrical response), and emotions(happiness or sadness), and how machine learning could use those relationships to predict how people might respond to a new piece of music. The results, presented at a conference on the intersections of computer science and art, show how we may one day be able to engineer targeted musical experiences for purposes ranging from therapy to movies.

    2     “Once we understand how media can affect our various emotions, then we can try to productively use it for actually supporting or enhancing human experiences,” says Shrikanth Narayanan, a professor at USC and the principal investigator in the lab.

The researchers first searched music streaming sites for songs with very few plays, tagged either “happy” or “sad.”     3     Two reliably caused sadness and one reliably caused happiness. One hundred participants who hadn’t heard the songs before split into two groups, listened to all three pieces, and either took a special scan or wore pulse, heat, and electricity sensors on their skin and rated the intensity of their emotions on a scale of 0 to 10. The researchers then fed the data, along with 74 features for each song, into several machine-learning mathematical steps and examined which features were the strongest predictors of responses. They found, for example, that the brightness of a song (the level of its medium and high frequencies) and the strength of its beat were both among the best predictors of how a song would affect a listener’s heart rate and brain activity.

The research is still in very early stages, and it will be a while before more powerful machine-learning models will be able to predict your mental and physical reactions to a song with any precision. But the researchers are excited about how such models could be applied: to design music for specific individuals, to create movie soundtracks easily arousing sympathy, or to help patients with mental health problems stimulate specific parts of their brain.     4     They want to start trying music-based therapies as well.