Asssessing preferences and abilities
To reach this conclusion, the researchers measured two things. First, they assessed the females' preferences by observing which males they spent the most time with. This part of the study yielded a new insight: male zebra finch courtship displays are differentiated by two key traits, duration and complexity.
Next, the researchers assessed the males’ cognitive abilities using standardized tests. For example, the birds had to learn to associate a colour with a food reward, a skill that, in nature, is essential for finding food and avoiding danger. The speed with which the birds learned and their final performance on the test were used to gauge their cognitive abilities.
The researchers found that the males with more complex dances were more attractive to females, were in better physical condition—demonstrating better endurance, coordination and energy—and, to a lesser extent, exhibited stronger motor learning performance. However, there was no evidence that they were more intelligent.
“A female will choose such a partner because he is likely to pass on better genes to her offspring, feed them better and be more involved in caring for them, thus maximizing their chances of survival,” Dubois explained.
Not a conscious decision
Observations indicate that females have consistent and repeated preferences. Does it mean they are making a conscious decision? Probably not.
“This is a somewhat anthropomorphic question,” Barou-Dagues said. “We can’t get inside an animal’s head and probe their thinking. However, we do know that preferences for specific male traits are partly innate and partly learned, largely by observing older, more experienced females.”
In all likelihood, these preferences are mainly an evolutionary legacy. “Traits linked to reproductive advantages—such as good physical condition—naturally become attractive over time,” said Barou-Dagues. “Females don’t need to ‘understand’ why; they are simply predisposed to prefer certain signals.”
However, choosing a partner is still a decision. Distinguishing between two males with similar performances may demand closer scrutiny and more finer discrimination. How the female makes these distinctions isn’t always obvious to humans. While the duration of the dance is visible, its complexity—the variety and sequence of movements—is harder to discern.
The human angle
The researchers believe the study’s findings may have implications for humans as well. They note that some human studies suggest dance can reveal information about body symmetry, which is associated with health and genetic qualities. And intelligence is also a selection criterion for human partners.
How do birds and humans assess intelligence in a partner?
“In animals, it isn’t clear how a female determines which male is smarter,” Barou-Dagues said. “Humans can also use dance as a criterion for assessing intelligence, since symmetrical dances may indicate favourable environmental conditions for healthy development. But unlike birds, humans have other ways to evaluate a partner’s intelligence, such as humour and creativity.”
Dubois believes this study challenges the theory that intersexual selection based on dance displays influences the evolution of general cognitive abilities. It also foregrounds modular cognitive traits, such as motor learning.
“Future research should explore the relationships between multisensory mating signals—such as song, dance and plumage colouration—and cognitive abilities in order to understand how intersexual selection shapes cognitive evolution in both animals and humans,” Dubois said.
