To answer these questions, she took short excerpts from the top two Billboard hits from each year, from 1955 to 2009. She recruited a group of 20-year-olds, and had them respond to each song on several scales: Did they recognize the song? Did they like it? Did they have personal memories associated with the song? If so, was this memory from growing up and listening with parents? From listening alone? With others? Finally, what emotions did they associate with each song? Did they feel energized, or nostalgic? Sad, happy, angry? Krumhansl also gathered demographic information, including parents’ age, and information on listening habits, both growing up and current.

For analysis, Krumhansl grouped these song samples into five-year periods, so that each of 11 periods contained excerpts from ten songs. As she describes in a forthcoming article in the journal Psychological Science, she found that personal memories associated with songs increased steadily from birth to present day. This was not surprising: These music-evoked memories would presumably be part of the reminiscence bumps that these 20-year-olds would experience later in life.

What was surprising was this: There was a spike in personal memories associated with the music of the early 1980s, and also a sustained spike in personal memories linked to music of the ’60s — the entire decade. Remember that these young listeners were born around 1990, which means that they’re experiencing reminiscence bumps for music of previous generations. What do we make of these rich personal memories for music from before they were born?