Bumblebees have a way of looking both adorable and slightly overserved, wobbling from flower to flower like fuzzy little potatoes. They seem simple, almost carefree. But a new study suggests there’s far more happening beneath those tiny wings than meets the eye – and something that few people ever associate with bees.
In a groundbreaking new study, scientists at Southern Medical University in Guangzhou took a closer look at how bumblebees respond to positive experiences inside the nest. Rather than focusing on individual behavior, they wanted to understand the atmosphere of a colony and how the mood of a single bee might shift the rhythm of the group.
To examine how one bee’s mood might influence another, the researchers looked at colonies of buff-tailed bumblebee (Bombus terrestris) and designed a task that could capture the slightest changes in how the insects respond to uncertain cues. The setup began with training: Individual bees learned that one color signaled a sugar reward while another signaled none. Once they formed that association, the team introduced intermediate, ambiguous colors that fell between the two learned cues.
This approach, known as a judgment-bias test, reveals how optimistically or cautiously an animal interprets uncertainty. Bees in a positive state tend to approach ambiguous colors quickly, as though expecting good news, while less positive individuals approach slowly or avoid them altogether. This made the task ideal for detecting a subtle internal shift in the observer bees.
Once the bees were trained and their baseline responses were clear, the researchers introduced the key manipulation. They gave one bee a small droplet of sucrose and allowed her a brief, 30-second encounter with a companion, an “observer” bee that had received no reward. The interaction took place without scents, colored cues, or training signals of any kind, so the observer had nothing to imitate or learn directly. All she could do was register the rewarded bee’s behavior.
When tested afterward, the observer bees showed something striking. They approached the ambiguous colors with the same quick, confident responses as bees that had tasted the sugar themselves, suggesting an internal shift rather than simple excitement or social mimicry.
“These behaviours are hallmarks of an affective shift, not arousal or social copying,” explained corresponding author Fei Peng, in an email to New Atlas.
A separate control condition helped reveal what made this shift possible. When the same interaction took place in complete darkness, where bees could touch but not see each other, the effect disappeared. Without the visual cues of the rewarded bee’s lively movements, the observers showed no change in optimism at all. The comparison made it clear that sight, not scent or touch, was carrying the contagion.
Fei said the speed of the effect was one of the biggest surprises.
“The moment that surprised us most was when we first saw evidence of contagion after just a brief, 30-second social interaction," Peng noted. "The observer bees hadn’t received any reward themselves, yet their later judgments shifted in the same direction as the rewarded demonstrators. Realizing that bees could be indirectly influenced by another bee’s positive state, without any shared food or explicit cues, was both unexpected and very exciting for the team.”
This rapid shift adds weight to the broader conclusion that internal states in bumblebees are not confined to individuals. Earlier work had shown that bees can enter positive or negative modes on their own, but this study shows that those states can be socially transmitted.
Rather than acting solely as independent foragers, bumblebees appear to be shaped by the emotional tone of their companions, offering new insight into how this species interacts and adapts.
The findings also raise deeper questions about what shifts inside an observer bee during those brief moments of contact. Peng noted that the behavioral pattern they documented closely resembles what is known about reward pathways in insects.
“In our study we did not measure neurotransmitters directly, but the behavioural pattern we observed in the observers, such as greater ‘optimism’ toward ambiguous cues, resembles the effects seen when dopamine levels are experimentally elevated," Peng said. "It is therefore reasonable to hypothesize that the observer’s internal state may have shifted through a dopaminergic mechanism after interacting with the rewarded demonstrator.”
While still speculative, this mechanistic angle offers a promising direction for understanding how internal states arise and how swiftly they might travel between individuals. It also raises the equally important question of whether negative states could spread just as easily. As the researcher explained, “If we assume positive affective states can spread, then negative ones such as stress from disturbance may also spread among bees.”
This perspective suggests that welfare in managed or agricultural settings involves more than nutrition and disease control. A calmer, low-stress atmosphere might matter just as much, especially if the mood of a few bees can subtly nudge the whole group.
Taken together, the results show that a positive state can pass between bees through nothing more than a moment of visual contact, adding nuance to what we know about insect social life. As researchers look deeper into how these changes form and spread, this work highlights how even small animals can shape each other in ways we’re only beginning to appreciate.
The team’s next steps will focus on what drives these shifts beneath the surface. While the current study centered on behavior, Peng hopes to explore how internal states arise and move between individuals, including the neural pathways that might support contagion. Understanding those circuits could help explain why such brief interactions leave lasting traces.
“We are very interested in the neural basis of contagion, and we do have some ideas for how to move forward, though these plans are still at an early stage," he suggested.
The researchers remain cautious about calling the effect “happiness,” but the finding still leaves an impression. If one bee’s internal state can influence another in just 30 seconds, it suggests that their moment-to-moment experience may be richer than the simple foraging routines we usually imagine.
The study makes no claim about emotion in the human sense, yet it hints that there is more unfolding behind a bee’s behavior than pure instinct. Even tiny animals may carry traces of internal life. Quiet, fleeting, but noticeable enough to shape those around them.
This study was published in the journal Science.
Source: Science
