Open source low-cost device to register dog’s heart rate and tail movement

In dogs, the perception of an important stimulus can be related to physiological changes such as the heart rate (e.g., in socioemotional situations with humans or dogs) and the movement of their tail (for example, tail-wagging has a bias that depends on the nature of the stimulus, a bias to the left is related to a withdrawal tendency and a bias to the right is related to an approach tendency ).<br>Although heart rate and the tail movement are important gateways to understanding dog cognition, just a few studies report these variables. Perhaps this is related to the difficulty of obtaining records of these variables in natural environments (e.g., parks), the elevated cost of commercial data acquisition hardware (around 5,000 USD) or by nonexistence of a tail-movement registering device. For these reasons, the goal of this brainhack project is to design and build a low cost device able to register the heart rate and changes in the tail movement in dogs, both in laboratory and in free movement conditions.<br>We decided to base our design in Arduino hardware for its accessibility and broad use. <br>In order to assess if the device could reliably get readings from a dog, we tested it in three phases: baseline, stimulation/no-stimulation and free movement. All phases lasted two minutes and were repeated twice on two dogs. In both, baseline and stimulation/no-stimulation, the dog stayed in sphinx position without movement restrictions but under the command stay. The stimulation/no-stimulation phase consisted in three interleaved repetitions of two types of conditions, stimulation and no-stimulation, each repetition lasted 20s. In the stimulation condition the dog owner showed the dog a treat and mentioned the dogs name. In the free movement condition, the dog walked down a street without any specific command.<br> The results showed that the device could be used to distinguish between two different stimulation conditions. In the stimulation/no-stimulation phase a Wilcoxon Signed Rank Test revealed statistically significant differences (p &lt; 0.05) between the beats per minute, beat amplitude and the tail movement amplitude.<br> By matching the data collected with observations of the movement of the tail, we notice that the data reflects the position of the tail but its resolution depended on the position of the electrode. The data acquired from the free movement condition was affected by the movement and did not seem reliable for testing.<br>We were able to build and test a non-invasive low cost device with the capacity to register the heart rate and the tail movement of dogs. We consider that the addition of a movement sensor could provide additional data to reduce the change on the signal due to movement.<br>This device can be integrated in future research on dog cognition. It can also be used in shelters and homes to easily measure the responses that dogs present to different sets of stimuli; for example, when a dog is left alone in its house and shows stress (i.e. increased heart rate, preferential tail movement to the left) the dogs care giver could make changes in the environment to increase the well-being of the dog.<br>The low cost and the easy access to the materials needed to build the device make it a feasible option to study dog cognition.在犬类中，对重要刺激的感知可与多种生理变化相关联，例如心率变化（如在与人类或其他犬只的社会情感互动场景中）以及尾部运动特征：具体而言，犬类摇尾存在方向偏向性，该偏向性由刺激性质决定——向左偏的摇尾对应退缩倾向，向右偏的摇尾则对应趋近倾向。 尽管心率与尾部运动是解析犬类认知的重要切入点，但目前仅有少量研究对这两类变量进行记录与报道。这一现状可能源于：在自然环境（如公园）中获取此类变量的记录存在难度，商用数据采集硬件成本高昂（约5000美元），且目前尚无专用的犬类尾部运动记录设备。基于上述原因，本次brainhack项目的目标为设计并构建一款低成本设备，使其可在实验室环境与自由活动场景下，同步记录犬类的心率与尾部运动变化。 鉴于Arduino硬件具备易用性与广泛的应用基础，本项目选择以其作为设计核心。 为评估该设备能否可靠采集犬类生理数据，本项目设置了三阶段测试流程：基线期、刺激/非刺激期与自由活动期。所有阶段均持续2分钟，且在两只犬只上各重复测试两次。在基线期与刺激/非刺激期内，犬只需保持斯芬克斯姿势（sphinx position），无运动束缚，但需服从“静止”指令。刺激/非刺激期包含两类条件的三次交替重复：刺激条件与非刺激条件，单次重复时长为20秒。刺激条件下，犬主会向犬只展示零食并呼唤其名字。自由活动期内，犬只可在无特定指令的情况下沿街道行走。 测试结果表明，本设备可有效区分两类不同的刺激条件。在刺激/非刺激期内，通过威尔科克森符号秩检验（Wilcoxon Signed Rank Test）分析可知，每分钟心跳数、心跳振幅与尾部运动振幅均存在统计学意义上的显著差异（p < 0.05）。 将采集到的数据与尾部运动观测结果进行比对后发现，设备采集的数据可反映尾部位置，但数据分辨率取决于电极的安放位置。自由活动期采集到的数据受运动干扰较大，暂不适合用于测试分析。 本项目成功构建并测试了一款非侵入式低成本设备，可实现犬类心率与尾部运动的记录。我们认为，若添加运动传感器，可采集额外数据以抵消运动对信号带来的干扰。 该设备可应用于未来的犬类认知研究中，同时也可在动物收容所与家庭场景中，便捷地测量犬只对不同刺激集的反应。例如，当犬只独自在家并表现出应激状态（即心率升高、尾部向左偏的运动偏好）时，饲养者可通过调整环境来提升犬只的福祉水平。 该设备构建所需的材料成本低廉且易于获取，使其成为犬类认知研究的可行方案。