What makes birdsong pleasing to the human ear? New study offers clues

Courtesy of Dr. Randler

When birds are chirping, humans may feel a little more at ease. But some bird vocalizations seem to strike a particularly pleasing chord with human ears — and scientists are beginning to understand why.

For much of our evolutionary history, the sounds of birds going about their business may have been a reassuring signal that the surrounding environment was free of danger.

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Now, a small new study has revealed that certain acoustic qualities may help explain why humans find some birdsongs more pleasant than others. People tended to prefer softer bird sounds with a narrower frequency range, while also rating more complex vocalizations as more pleasant, according to researchers at the University of Tübingen in Germany.

And the preference didn’t appear to depend on whether listeners knew much about birds, the scientists found.

“This suggests that enjoyment of birdsong is connected to something more fundamental than just knowing what you are listening to,” said Dr. Nadine Kalb, lead author of the study published September 1 in the journal Frontiers , in a statement .

“Our results show that the combination of various acoustic features is important for how much we like a bird song, and that different combinations of these acoustic characteristics can result in very pleasant sounds,” added Kalb, a biologist at the University of Tübingen, in an email.

The researchers said the findings could provide a better understanding of how birds shape our environment — and eventually help inform the design of parks, urban green spaces and other places where people go to unwind.

“Perhaps the most important takeaway is that paying attention to birds can change the way we experience the natural world,” senior study author Dr. Christoph Randler said. “Even when we do not understand what a bird is communicating, its song can attract our attention, evoke positive feelings and make us more aware of the biodiversity around us.”

The research team asked 84 people to listen to recordings of 123 wild bird species and rate how pleasant they found each bird’s vocalizations.

The star of the survey, with an average rating of 4.52 out of 5, was the common blackbird (or the Eurasian blackbird). Typically spotted in gardens, parks and woodlands, Turdus merula is a familiar sight across Europe, with a song that’s rich, mellow and flutelike .

At the other end of the spectrum was the barn owl, whose vocalizations received an average rating of 1.32. The barn owl’s call is an eerie, raspy screech. Among other surveyed birds, the European goldfinch received a pleasantness score of 4.26 out of 5, followed by the European robin at 4.04 and the blue tit at 3.92.

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What makes one bird sound pleasant and another less so? That question was at the heart of what Kalb and Randler, a professor of biology at the University of Tübingen, wanted to understand.

“Our interest developed from a broader question: why do some encounters with birds feel particularly positive to people? In our previous research , we had already found that birds and birdwatching can contribute to psychological restoration and well-being,” Randler said in an email.

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This time, the researchers wanted to look more closely at the sounds themselves — bringing together “the biology of the bird’s vocalization and the psychology of human perception,” Randler said. After asking people to rate the birdsongs, the researchers then cross-referenced the ratings with the songs’ acoustic characteristics to determine which features made them sound more melodic.

One of the most surprising findings, Randler said, was that people tended to prefer more intricate birdsongs. “We might intuitively expect simple, repetitive sounds to be easier and therefore more pleasant, but the opposite pattern emerged: more complex sounds tended to receive higher pleasantness ratings,” he noted.

The findings could eventually help city planners and park designers think differently about noisy places, according to the researchers. Instead of focusing only on reducing noise, officials could also pay more attention to the kinds of sounds people hear, including natural ones such as birdsong.

But Randler stressed that the research is still in early days — simply adding more birdsong to spaces may not be the answer. Playing extra birdsong through loudspeakers did not provide greater well-being benefits than naturally occurring birdsong, his team found in previous research .

“It reminds us that bird vocalizations have an important dimension beyond communication between birds: they also form a major part of the soundscape experienced by humans,” Randler said.

Dr. Olga Feher, an associate professor of psychology at the University of Warwick in England who studies birdsong, said, “The findings suggest that there are at least some biological factors in human birdsong preference.” Feher was not involved with the new study.

Feher pointed to other research that suggests some of our responses to sound may have deep evolutionary roots. A March study found that humans and other animals tend to share preferences for certain vocal sounds, while a 2020 study uncovered that human music and birdsong share certain rhythmic patterns.

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But personal experience can also shape those preferences, Feher said. She studies zebra finches, whose fast, robotic songs are often considered unpleasant, “but I really like them myself, no doubt due to the pleasant associations,” she said in an email.

She added that while the new paper suggests we can use the information to improve the design of acoustic environments for humans, a focus on charismatic species with melodious songs can have a harmful effect on conservation efforts for those with less pleasant songs.

“To me, the most interesting thing about this research is that it tells us something about the evolution of our perception of beauty, and that this is something we share with certain songbirds who sing to entertain and impress their conspecifics,” Feher said, referring to members of the same species.

Dr. Robert Lachlan, an animal communication researcher and associate professor of psychology at Royal Holloway, University of London, said the study opens the door to a new area of research, but more work is needed to understand exactly what makes some birdsongs appealing to humans.

He questioned whether higher-frequency songs are necessarily more attractive, noting that birds known for beautiful songs, such as blackbirds and nightingales, often use relatively low-pitched, flutelike notes.

“I’d not be surprised if there are regions of the frequency scale, for example, that we tend to find more attractive,” Lachlan said. This preference might not have been detected by looking only at the highest and lowest frequencies in the songs, he added.

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He noted that biology and personal experience are also likely to shape how people perceive birdsong. “I think that it was interesting that birding experience had no effect on which songs were found to be attractive in this study,” Lachlan said in an email. “I think there are other dimensions here — I know I feel differently when returning home from traveling and hear familiar birds in my neighbourhood.”

Kalb, lead study author, said the findings suggest there is no single formula for a pleasant bird sound. “The blackbird, willow warbler and blackcap sound quite different from one another, yet all received very high pleasantness ratings,” she said. “Our findings are not about one acoustic feature in isolation, but rather that the combination of frequency, amplitude and bandwidth is important for how pleasant a bird sound is perceived.”

Randler agrees that there is more work to be done. “The study establishes which acoustic characteristics are associated with pleasantness; it does not yet tell us exactly why our brains prefer those characteristics,” Randler said, adding that the next step is to understand why people prefer certain birdsongs and whether those preferences hold across different cultures and environments.

承蒙兰德勒博士惠允

鸟儿鸣叫时，人们可能会感到更加放松。但有些鸟类的叫声似乎特别悦耳动听——科学家们也开始了解其中的原因。

在我们的进化史的大部分时间里，鸟儿们忙碌的鸣叫声可能是一种令人安心的信号，表明周围的环境是安全的。

景迈·奥康纳/菲尔德博物馆

有些鸟类在导致恐龙灭绝的小行星撞击中幸存了下来。化石化的鸟粪可以帮助解释原因。

一项新的小型研究表明，某些声学特性或许可以解释为什么人类觉得某些鸟鸣声比其他鸟鸣声更悦耳。德国图宾根大学的研究人员发现，人们往往更喜欢频率范围较窄、音调较柔和的鸟鸣声，同时也认为更复杂的鸣叫声更悦耳。

科学家发现，这种偏好似乎与听众是否了解鸟类无关。

“这表明，欣赏鸟鸣与一些比仅仅知道你在听什么更根本的东西有关，”该研究的主要作者纳丁·卡尔布博士在一份声明中说。该研究于 9 月 1 日发表在《前沿》杂志上。

“我们的研究结果表明，各种声学特征的组合对于我们有多喜欢鸟鸣声非常重要，而且这些声学特征的不同组合可以产生非常悦耳的声音，”蒂宾根大学的生物学家卡尔布在一封电子邮件中补充道。

研究人员表示，这些发现可以让我们更好地了解鸟类如何塑造我们的环境，并最终有助于指导公园、城市绿地和其他人们放松身心的场所的设计。

“或许最重要的结论是，关注鸟类可以改变我们体验自然世界的方式，”该研究的资深作者克里斯托夫·兰德勒博士说。“即使我们不明白鸟儿在表达什么，它们的鸣叫也能吸引我们的注意力，唤起积极的情感，并让我们更加意识到周围的生物多样性。”

研究团队请 84 人聆听 123 种野生鸟类的录音，并评价他们对每种鸟类鸣叫声的愉悦程度。

本次调查的明星物种是普通黑鹂（或称欧亚黑鹂），平均评分高达 4.52 分（满分 5 分）。这种鸟常见于花园、公园和林地，学名 Turdus merula，在欧洲各地都很常见，其鸣叫声悠扬、柔和，宛如长笛。

与之形成鲜明对比的是仓鸮，它的鸣叫声平均得分仅为1.32分。仓鸮的叫声是一种怪异而沙哑的尖叫声。在其他受调查的鸟类中，欧洲金翅雀的悦耳度得分最高，为4.26分（满分5分），其次是欧洲知更鸟（4.04分）和蓝山雀（3.92分）。

教育图片/环球图片集团/盖蒂图片社

猫头鹰“醒目”的羽毛颜色应该会阻碍捕猎。科学家们或许已经找到了其中的奥秘。

为什么有些鸟的叫声悦耳动听，而有些鸟的叫声却不那么悦耳？这个问题正是卡尔布和图宾根大学生物学教授兰德勒想要了解的核心问题。

兰德勒在一封电子邮件中说：“我们的兴趣源于一个更广泛的问题：为什么有些人与鸟类的接触会给人带来特别积极的感受？在我们之前的研究中，我们已经发现鸟类和观鸟可以促进心理健康和幸福感。”

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这一次，研究人员希望更仔细地研究鸟鸣声本身——兰德勒说，这需要将“鸟类发声的生物学原理与人类感知的心理学原理结合起来”。在请人们对鸟鸣声进行评分后，研究人员将评分与鸟鸣声的声学特征进行交叉比对，以确定哪些特征使鸟鸣声听起来更悦耳动听。

兰德勒表示，最令人惊讶的发现之一是，人们往往更喜欢复杂的鸟鸣声。“我们可能凭直觉认为简单重复的声音更容易接受，因此也更悦耳，但结果却恰恰相反：更复杂的声音往往获得更高的愉悦度评分。”他指出。

研究人员表示，这些发现最终可能有助于城市规划者和公园设计师以不同的视角看待嘈杂场所。除了关注降低噪音之外，相关部门还可以更加关注人们听到的声音类型，包括鸟鸣等自然声​​音。

但兰德勒强调，这项研究仍处于早期阶段——简单地在空间中增加鸟鸣声可能并非解决之道。他的团队此前的研究发现，通过扬声器播放额外的鸟鸣声并不能比自然发生的鸟鸣声带来更大的幸福感。

兰德勒说：“这提醒我们，鸟类的鸣叫声除了鸟类之间的交流之外，还有一个重要的维度：它们也是人类所体验到的声音环境的重要组成部分。”

英国华威大学心理学副教授奥尔加·费赫尔博士专门研究鸟鸣，她说：“研究结果表明，人类对鸟鸣的偏好至少存在一些生物学因素。”费赫尔博士并未参与这项新研究。

费赫尔指出，其他研究表明，我们对声音的某些反应可能具有深远的进化根源。三月份的一项研究发现，人类和其他动物往往对某些声音有共同的偏好，而2020年的一项研究则揭示了人类音乐和鸟鸣声具有某些共同的节奏模式。

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研究人员称，一只蓝松鸦和一只绿松鸦交配了。它们的后代堪称科学奇迹。

但费赫尔表示，个人经历也会影响这些偏好。她研究斑胸草雀，这种鸟的鸣叫声快速而机械，通常被认为不悦耳，“但我自己却很喜欢，毫无疑问是因为这些鸣叫声能唤起美好的联想，”她在电子邮件中写道。

她补充说，虽然这篇新论文表明我们可以利用这些信息来改进人类声学环境的设计，但专注于歌声悦耳动听的魅力物种可能会对那些歌声不太悦耳的物种的保护工作产生有害影响。

“对我来说，这项研究最有趣的地方在于，它告诉我们一些关于我们对美的感知演变的信息，而且这是我们与某些鸣禽所共有的，它们唱歌是为了娱乐和打动同类，”费赫尔说，他指的是同一物种的成员。

伦敦大学皇家霍洛威学院心理学副教授、动物交流研究员罗伯特·拉克兰博士表示，这项研究开启了一个新的研究领域，但还需要更多的工作来了解究竟是什么让某些鸟鸣声对人类有吸引力。

他质疑高频鸣叫是否一定更具吸引力，并指出以优美鸣叫著称的鸟类，如黑鸟和夜莺，经常使用相对低沉、类似笛子的音调。

“如果频率范围内存在一些我们更偏爱的频率区域，我不会感到惊讶，”拉赫兰说道。他还补充说，这种偏好可能无法通过仅仅观察歌曲中的最高频率和最低频率来发现。

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他指出，生物学因素和个人经历也可能影响人们对鸟鸣的感知。“我认为这项研究很有意思，观鸟经验对人们认为哪些鸟鸣动听并没有影响，”拉克兰在一封电子邮件中写道。“我认为这里还有其他因素——我知道，旅行回家后听到熟悉的鸟鸣声，我的感受会不一样。”

该研究的主要作者卡尔布表示，研究结果表明，悦耳的鸟鸣声并非只有一个固定的模式。“乌鸫、柳莺和黑顶莺的叫声截然不同，但它们的悦耳度评分都非常高，”她说。“我们的研究结果并非孤立地看待某个声学特征，而是强调频率、振幅和带宽的组合对于鸟鸣声的悦耳程度至关重要。”

兰德勒也认为还有更多工作要做。“这项研究确定了哪些声学特征与悦耳感相关；但它尚未告诉我们大脑为何偏爱这些特征，”兰德勒说，并补充道，下一步是了解人们为何偏爱某些鸟鸣声，以及这种偏好是否在不同的文化和环境中都成立。