The findings add to a growing body of work suggesting that ape minds can imagine scenarios beyond the “here-and-now,” a skill once thought to be unique to humans. Human children begin playing pretend as early as 12 months old and master the ability to build imaginary worlds by age 3. Many high-level thinking tasks are possible only because we can imagine things that aren’t really there.

The study centered on Kanzi, a remarkable bonobo who could communicate using word-linked symbols called lexigrams. Amalia Bastos, a comparative psychologist at the University of St Andrews in Scotland, first met him in 2023. “We were starstruck by Kanzi,” she says.

During their first meeting, the bonobo used his lexigram-studded board to ask Bastos and a colleague to chase each other. Bastos noticed that even though they only pretended to play, Kanzi still enjoyed watching them. This kick-started a series of make-believe tests that Bastos and Christopher Krupenye, a psychologist at Johns Hopkins University, designed for Kanzi.

In the first of these tests, Kanzi sat at a table with two glasses. An experimenter pretended to pour a glass of “juice” — Kanzi’s tipple of choice — into both cups from a see-through empty jug. The experimenter then poured the nonexistent contents of one cup back into the jug, before asking Kanzi which cup still held the “juice.” Kanzi guessed correctly 68 percent of the time, significantly above chance, the researchers report.

The guesses, Bastos says, may not have been definitive evidence of Kanzi’s internal imagination. “Kanzi is an old bonobo. Maybe his vision isn’t very good. Maybe he thinks that there’s real juice in these things,” she says.

The researchers retested Kanzi to see if he could identify real from fake juice. They presented him with two cups: one containing orange juice and an empty one that they filled with pretend juice. When asked which cup he wanted, Kanzi picked the real juice nearly 80 percent of the time, suggesting he had little issue identifying his reward. A third test that mimicked the first, but with pretend grapes rather than juice, again suggested Kanzi understood where pretend food was located.

More than a century ago, Pavlov trained his dog to associate the sound of a bell with food. Ever since, scientists have assumed the dog learned this through repetition. The more times the dog heard the bell and then got fed, the better it learned that the sound meant food would soon follow.

Now, scientists at UC San Francisco are upending this 100-year-old assumption about associative learning. The new theory asserts that it depends less on how many times something happens and more on how much time passes between rewards.

“It turns out that the time between these cue-reward pairings helps the brain determine how much to learn from that experience,” said Vijay Mohan K. Namboobidiri, Ph.D., an associate professor of Neurology and senior author of the study, published in Nature Neuroscience.

Scientists have discovered a brain signaling pathway that eliminates body fat without reducing food intake by targeting stubborn bone marrow fat cells.

Li et al. present a spatial transcriptomic atlas of the mouse paraventricular hypothalamus (PVH) and provide molecular markers for parabrachial-and spinal cord-projecting PVH populations. They further show that Brs3-expressing PVH neurons regulate satiety, as they co-express Mc4r, cause weight gain when silenced, and reduce food intake via parabrachial projections.