Caroline Casey and her team study the seals on Año Nuevo Island off the coast of California, and they have observed male elephant seals engaging in dominance displays year after year. This led them to wonder if the seals remembered their past bouts. To test this, the team would find a male seal returning to the island and play recorded calls from his old rivals. When males heard their most familiar dominant rival from the previous year, they reacted faster than they did to unfamiliar calls.

Automakers are required to design their vehicles so they emit sounds at low speeds to alert pedestrians to their presence, and researchers can design custom sounds to maximize their effectiveness. Mei Suzuki and her team’s efforts created a library of sounds and played them to volunteers, both in a studio and in real road conditions. They then asked the volunteers to rate each and found the best performer was a version of pink noise — a type of noise dominated by lower-frequency notes.