Babies hear rhythm at birth, ghrelin loss in snakes explains hunger, sleep fuels puzzle solving | NPR Shortwave

Three science stories anchor this episode of Shortwave: researchers show newborns can track rhythm from Bach even before melodies are learned, a cross-species genomic study finds some snakes and chameleons have lost the hunger hormone ghrelin, and a sleep study shows people are more likely to solve puzzles they dream about after REM sleep. Host Regina Barber and guest Juana Summers guide listeners through the methods and implications, including how rhythm perception might be rooted in biological rhythms and movement, and how dreaming may support problem solving and creativity. The stories illustrate how the brain, hormones, and sleep shape cognition from birth onward.

Overview

This Shortwave science episode from NPR threads together three investigations that illuminate how biology, sleep, and cognition intersect with everyday life. Regina Barber hosts with Rachel Carlson, and Juana Summers joins for a biweekly science roundup that blends neurobiology, evolution, and sleep research to show the brain’s surprising continuity from birth to adulthood.

Newborn rhythm perception

In a study published in PLOS Biology, scientists played Bach piano music to sleepy newborns while the infants wore EEG sensors to monitor brain activity. The goal was to identify brain signals indicating that the infant brain could predict the next note in a sequence. The researchers found that babies reliably track rhythmic structure even when rhythms become complex, suggesting an innate or early-developing sensitivity to rhythm. In contrast, melody tracking appeared not to engage the same neural circuits in the newborns, implying that melody perception may mature later or require more experience. Laurel Traynor, a developmental neuroscientist at McMaster University, explains that rhythm is deeply embedded in biology—heartbeat, movement, speech—and may be an ancient predictive trait for the human brain. The study used Western classical music to keep the stimulus consistent while exploring these foundational perceptual capabilities.

"Rhythm is everywhere." - Laurel Traynor

Ghrelin loss in snakes and reptiles

The second topic examines how some reptiles, including certain snakes and chameleons, have lost the gene that produces ghrelin, the hunger hormone. This genetic shift helps explain why these species can fast for extended periods and then consume a large meal, a feeding pattern that contrasts with typical human appetite regulation involving ghrelin and GLP-1 signaling. The work, reported in the Royal Society journals, links metabolic pathways in reptiles to broader questions about human energy balance and disease risk. Evolutionary biologist Alex Pyrin, interviewed for the piece, notes that studying these metabolic pathways in reptiles could illuminate human physiology and potential therapeutic avenues. A trivia note connects this line of inquiry to medicine: GLP-1–targeting drugs such as Ozempic were inspired in part by research on venomous creatures like the Gila monster, illustrating how cross-species biology can inform human health.

"studying these kinds of metabolic pathways in reptiles could tell us more about humans." - Alex Pyrin

Sleep, dreams, and problem solving

The final segment centers on a Northwestern University study led by cognitive neuroscientists investigating whether dreams can help solve problems. Twenty lucid dreamers were tasked with puzzles and given a three-minute window to solve them while awake; they then slept while researchers monitored REM sleep and played a unique soundtrack to cue dreaming about the unsolved puzzle. After waking, participants were more than twice as likely to solve puzzles they remembered dreaming about than those they did not remember dreaming about, suggesting dreaming can facilitate memory processing and creative insights. The study, published in Neuroscience of Consciousness, reinforces the idea that sleep not only consolidates day-to-day learning but may actively promote problem solving through dream content. Dream researcher Robert Stickgold is quoted as saying that dreams are not just entertainment, but a catalyst for processing information and boosting creativity.

"Dreams aren't just entertainment. They're a catalyst for processing information and inducing creativity." - Robert Stickgold

Closing thoughts and where to find more

As with other Shortwave episodes, the hosts point listeners toward additional NPR science coverage and invite further exploration of how sleep, rhythm, and metabolism shape human cognition. The piece also underscores how cross-disciplinary approaches—from neuroscience to evolutionary biology to sleep science—can yield practical insights about everyday experiences, from infant development to diet and dream-driven problem solving.

Listen to the full episode for more details, methods, and expert perspectives, and follow along with the linked studies to dive deeper into rhythm perception, ghrelin biology, and dream-based cognition.

"Rhythm is everywhere." - Laurel Traynor

"studying these kinds of metabolic pathways in reptiles could tell us more about humans." - Alex Pyrin

"Dreams aren't just entertainment. They're a catalyst for processing information and inducing creativity." - Robert Stickgold