Department of Psychology, Yale University, New Haven, CT 06520.
Department of Psychology, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2022 Oct 25;119(43):e2200257119. doi: 10.1073/pnas.2200257119. Epub 2022 Oct 17.
How infants experience the world is fundamental to understanding their cognition and development. A key principle of adult experience is that, despite receiving continuous sensory input, we perceive this input as discrete events. Here we investigate such event segmentation in infants and how it differs from adults. Research on event cognition in infants often uses simplified tasks in which (adult) experimenters help solve the segmentation problem for infants by defining event boundaries or presenting discrete actions/vignettes. This presupposes which events are experienced by infants and leaves open questions about the principles governing infant segmentation. We take a different, data-driven approach by studying infant event segmentation of continuous input. We collected whole-brain functional MRI (fMRI) data from awake infants (and adults, for comparison) watching a cartoon and used a hidden Markov model to identify event states in the brain. We quantified the existence, timescale, and organization of multiple-event representations across brain regions. The adult brain exhibited a known hierarchical gradient of event timescales, from shorter events in early visual regions to longer events in later visual and associative regions. In contrast, the infant brain represented only longer events, even in early visual regions, with no timescale hierarchy. The boundaries defining these infant events only partially overlapped with boundaries defined from adult brain activity and behavioral judgments. These findings suggest that events are organized differently in infants, with longer timescales and more stable neural patterns, even in sensory regions. This may indicate greater temporal integration and reduced temporal precision during dynamic, naturalistic perception.
婴儿如何体验世界是理解他们认知和发展的基础。成人体验的一个关键原则是，尽管我们持续接收感官输入，但我们将其感知为离散事件。在这里，我们研究了婴儿的这种事件分割，以及它与成人的不同之处。婴儿事件认知研究通常使用简化任务，其中（成人）实验者通过定义事件边界或呈现离散动作/小插曲来帮助婴儿解决分割问题。这预设了婴儿体验到的事件，并留下了关于婴儿分割原则的问题。我们通过研究婴儿对连续输入的事件分割，采用了一种不同的、数据驱动的方法。我们从清醒的婴儿（和成人，用于比较）观看卡通片时收集了全脑功能磁共振成像 (fMRI) 数据，并使用隐马尔可夫模型来识别大脑中的事件状态。我们量化了跨脑区的多个事件表示的存在、时间尺度和组织。成人大脑表现出已知的事件时间尺度层次结构，从早期视觉区域的较短事件到后期视觉和联想区域的较长事件。相比之下，婴儿大脑仅表示较长的事件，即使在早期视觉区域也是如此，没有时间尺度层次结构。定义这些婴儿事件的边界仅部分与从成人大脑活动和行为判断定义的边界重叠。这些发现表明，即使在感觉区域，事件在婴儿中也以不同的方式组织，具有更长的时间尺度和更稳定的神经模式。这可能表明在动态、自然感知期间存在更大的时间整合和降低的时间精度。
