揭示潜在因子不可确定性,解释为何高维数据表征仍存根本性不确定性。
Perspectives on Latent Factor Indeterminacy and its Implications for Data Representation
- 从生成模型视角分析潜在因子投影的不可确定性问题
- 当特征维度无限增大时,潜在因子才具备完全可确定性
- 对心理测量、统计与人工智能领域有深远影响,适合高维数据建模
因子分析模型与赫姆霍兹机、玻尔兹曼机相关,可视为线性自编码器或单隐层生成神经网络,因此可作为研究深度生成模型基础特性的最小模型。本文聚焦潜在因子投影的固有不确定问题:即使已知潜在向量的内在维度、满足正则条件且旋转不变性已被解决,因果潜在源的恢复仍存在本质不确定性——结果将不确定、分布偏离且不唯一。这一现象对数据表征具有重大影响,却仍被从业者和理论家忽视。该经典心理测量问题与变分自编码器中的潜在变量坍缩现象密切相关。我们从多个角度评估此不确定性的数学与概念关联,并讨论其对心理测量学、统计学和人工智能领域的启示。研究表明,当特征维度趋于无穷时,潜在因子在所有方面都具备可确定性,这使得在样本情况下特征数极大时可采用本质上无需分布假设的估计方法。结论是,这些性质在规模下涌现,表明因子模型适用于超高维数据的表示学习。
原文摘要 · Abstract (English)
The common factor analytic model is related to Helmholtz and Boltzmann machines, can be conceived as a linear autoencoder, or can be thought of as a single-hidden-layer generative neural network. We thus consider it a basal generative representation learner that can be used as a minimal model for studying the foundational characteristics of (deep) generative model architectures. We focus on the fundamental problem of indeterminacy in latent factor projections. This indeterminacy implies that, even when the intrinsic dimension of the latent vector is known, regularity conditions are met, and rotational indeterminacy is resolved, an inherent indefiniteness in the retrieval of causative latent sources remains: they will be uncertain, distributionally deviant, and non-unique. This can have major implications for data representation but remains an elusive issue, even to practitioners and theorists well-versed in the factor model. Moreover, this classic psychometric problem is intricately related to the modern issue of latent variable collapse in the variational autoencoder framework for deep generative modeling. Here, we assess this indeterminacy from various perspectives and show how these are mathematically and conceptually related and we discuss subsequent implications for the Psychometrics, Statistics, and Artificial Intelligence communities. We show that one has latent factor determinacy across all its facets when the feature-dimension grows to infinity. This feeds into an essentially distribution-free estimation approach in the sample case when the number of features grows very large. We conclude, as these are emergent properties at scale, that the factor model is suited for representation learning of very-high-dimensional data.
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