Department of Biology, University of Pittsburgh at Johnstown, Johnstown, PA 15904, USA.
Anim Cogn. 2012 Jul;15(4):647-56. doi: 10.1007/s10071-012-0493-y. Epub 2012 Apr 10.
Complex acoustic signals in many animal species are characterized by a syntax that governs how different notes are combined, but the importance of syntax to the communicative function of signals is not well understood. Mated pairs of yellow-naped amazons, Amazona auropalliata, produce coordinated vocal duets that are used for territory maintenance and defense. These duets follow rules that specify the ordering of notes within duets, such as a strict alternation of sex-specific notes and a defined progression of note types through each duet. These syntactical rules may function to define sex-specific roles, improve coordination, and allow individuals to combine calls into meaningful sequences. As a first step toward understanding the functional significance of syntax, we conducted two separate audio playback experiments in which we presented nesting pairs with normal duets and duets with broken syntax (i.e., one of the syntactic rules was broken). In Experiment One, we reversed the order of female and male notes within note pairs while retaining the typical progression of note types through a duet. In Experiment Two we reversed the order of note types across a whole duet while retaining the typical female-male ordering within note pairs. We hypothesized that duets with broken syntax would be less-effective signals than duets with normal syntax and predicted that pairs would respond less to broken syntax than to normal duets. Contrary to predictions, we did not observe differences in response between treatments for any variables except latency to approach the speaker. After we combined data across experiments post hoc, we observed longer latencies to approach the speakers after playbacks of broken syntax duets, suggesting that pairs could differentiate between playbacks. These responses suggest that breaking one rule of duet syntax at a time does not result in detectable loss of signal efficacy in the context of territorial intrusions.
在许多动物物种中，复杂的声音信号的特点是有一种语法，它控制着不同音符的组合方式，但语法对信号的交际功能的重要性还没有得到很好的理解。黄颈亚马逊鹦鹉的交配对会产生协调的声乐二重奏，用于维持和防御领地。这些二重奏遵循规定了二重奏中音符顺序的规则，例如严格交替特定性别的音符和在每个二重奏中定义的音符类型的递进。这些句法规则可能有助于定义特定性别的角色、提高协调性，并允许个体将叫声组合成有意义的序列。作为理解语法功能意义的第一步，我们进行了两个独立的音频播放实验，在实验中，我们向筑巢对播放正常的二重奏和语法错误的二重奏（即打破了一个语法规则）。在实验一，我们在保留每个二重奏中典型的音符类型递进的情况下，改变了音符对中雌雄音符的顺序。在实验二，我们保留了音符对中典型的雌雄排序，改变了整个二重奏中音符类型的顺序。我们假设语法错误的二重奏会比正常语法的二重奏更无效，并预测对配对的反应会比正常二重奏更差。与预测相反，除了接近扬声器的潜伏期外，我们没有观察到处理之间任何变量的反应差异。在我们对实验进行事后组合数据后，我们观察到在播放语法错误的二重奏后，接近扬声器的潜伏期更长，这表明配对可以区分播放。这些反应表明，在领土入侵的情况下，一次打破一个二重奏语法规则不会导致信号功效的明显损失。
