Bumblebees at work in an emotion-like state
C. M. S. Plowright
Published online: 3 April 2017
Psychonomic Society, Inc. 2017
Summary Pretest sucrose affects a dopamine-modulated re-
sponse of bumblebees to an ambiguous cue to reward as well
as a response to a simulated attack (Perry, Baciadonna, &
Chittka, Science, 353(6307), 1529–1531, 2016). The contribu-
tion of the study lies in opening the door to research on the inner
experience of insects, the learning and motivational mechanisms
of their behavior, and the evolutionary analysis of emotions.
Do ravens have insight into problems? Do dolphins have lan-
guage? Do elephants have a self-concept? Sound familiar? These
questions are too broad and sweeping to tackle, betray an anthro-
pocentric approach to animal behavior, and make headlines
(Shettleworth, 2010). Do bees have emotions? All right, do they
have emotion-like states? According to Perry, Baciadonna, and
Chittka (2016) in a recent paper in Science, they do. The paper is
sure to cause behavioral scientists to take notice, and not only for
its tantalizing title: BUnexpected rewards induce dopamine-
dependent positive emotion-like state changes in bumblebees^.
For the readership from psychology (especially in the areas of
learning, motivation, and cognition), it touches on many ques-
tions that animate our research programs.
The approach, pioneered by Bateson, Desire, Gartside and
Wright (2011), was to adopt specific behavioral, cognitive
and physiological indices of the emotions in humans and other
vertebrates, and apply them to bees. Bumblebees were first
trained on a go/no-go task. A reinforcer of 30% sucrose was
signaled by one color (e.g. blue) on one side of the foraging
arena, while water was signaled by another color (e.g. green) on
the other. The trained bees were then tested for their reaction to
an ambiguous blue-green card in the middle. How did the bees
interpret this ambiguous stimulus? Bees in a group that was fed
a drop of 60% sugar solution prior to entering the arena directed
themselves to the stimulus significantly more quickly than a
control group. The authors took pains to rule out the possibility
that the pretest consumption of sugar simply led to higher ac-
tivity levels or to a higher expectation of subsequent reward.
The conclusion that there was a cognitive bias in judgment was
all but inescapable. If this is part of what is meant by positive
emotion or optimism, then the bees have it.
There was more. Perhaps a little taste of sugar could, well, take
the sting . . . out of a potentially unpleasant experience, such as
being attacked by a predator. Here, a new and ingenious method
was developed. Bees were first trained to forage in the arena.
Then, during testing, two things happened: (1) In a little ante-
chamber at the entrance of the foraging arena, one group of bees
was given a droplet of 60% sugar, while the other one was not; (2)
10 seconds later, an attack on the bees in both groups was simu-
lated: the sponge-covered ceiling in the antechamber literally
came down on a captive worker for 3 seconds, after which it
was released. How long it took the bees to just get over the
experience was measured. The prefed group started foraging sig-
nificantly more quickly than the control group.
The icing on the cake in this series of experiments was a
neuropsychological consideration. Given that dopamine mediates
reward-related processes, a dopamine blocker was expected to
abolish both the effects of pretest sucrose described above. It did.
Theories of learning and motivation The results present new
opportunities for investigating ‘killjoy’ interpretations. Perhaps
what is already known about learning and motivation will go a
long way towards explaining the findings reported here. Below,
* C. M. S. Plowright
School of Psychology, University of Ottawa, Ottawa, ON, Canada
Learn Behav (2017) 45:207–208