Choice overload is the paradoxical phenomenon where decision making is harder when you’re presented with more options. In humans, it can be seen in choices such as which film to watch, which dish to order from a menu, and even when it comes to online dating.
But this isn’t unique to humans, as researchers suggest that when female treefrogs receive too many male mating calls, they’re less successful in choosing a mate.
From May to August, male Cope’s gray treefrogs gather in large, noisy choruses to attract a mate. Sustained noise levels in these choruses average between 70–80 decibels; the equivalent of a busy road with traffic, or the sound of a hairdryer.
The resulting wall of sound can make it difficult for female frogs to identify a suitable mate. Previous studies have focused on the factor of ‘energetic masking’ (where overlapping calls make individuals difficult to hear) across mammals, birds and frogs. But researchers from the Smithsonian Tropical Research Institute and the University of Tennessee specifically wanted to study choice overload.
“We were really interested in disentangling why female treefrogs have trouble finding a mate – whether it’s because they have trouble hearing males against a noisy backdrop, or if the females simply become overwhelmed by the number of options,” explains Claire Hemingway, a research associate at the Smithsonian Tropical Research Institute and an assistant professor at the University of Tennessee, as well as the paper’s lead author.
“In human terms, is it like entering a crowded bar and not being able to hear anyone talk, or is it like using a dating app and not being able to choose among the many options?”
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The mating game
To specifically investigate choice overload, the researchers played recorded mating calls through speakers in a laboratory at the Smithsonian Tropical Research Institute, presenting female treefrogs with one long ‘target’ call and one, three or seven shorter ‘distractor’ calls.
The difference in call duration between the target and distractor calls was deliberately significant and based on previous studies of sexual selection in Cope’s gray treefrogs.
These were also tested in two conditions, one with no chorus noise and one with chorus noise.
As the number of mating calls increased, the frogs’ ability to make decisions declined. When presented with two calls, females ‘pursued’ their mate 97% of the time. When this increased to eight, the percentage dropped to 82%.
Another significant finding was that when females did make a choice, it took them far longer and they were less likely to select the target mating call. When two calls were played, females selected the target 76% of the time in an average of 114 seconds. With eight calls, target selection dropped to 25% and average decision time increased to 183 seconds.
“We were shocked by how straightforward the results were,” says Jessie Tanner, an assistant professor at the University of Tennessee and the paper’s senior author.
“With or without noise, when we presented more calls to the females at once, their performance declined in several ways.”
While male treefrog calls often overlap in the wild, allowing both energetic masking and choice overload to impair cognitive choice, the controlled settings of this study allowed the calls to be played sequentially.
As there were significant declines in performance, this suggests that treefrogs are also susceptible to choice overload. These cognitive constraints may influence sexual selection across more animals than previously thought – not just in humans.
Read the full paper here: Choice overload constrains mate choice independent of energetic masking
