  This study investigates how learners organize perceptual space in early
phonetic acquisition by advancing previous studies in two key aspects. Firstly,
it examines the shape of the learned hidden representation as well as its
ability to categorize phonetic categories. Secondly, it explores the impact of
training models on context-free acoustic information, without involving
contextual cues, on phonetic acquisition, closely mimicking the early language
learning stage. Using a cross-linguistic modeling approach, autoencoder models
are trained on English and Mandarin and evaluated in both native and non-native
conditions, following experimental conditions used in infant language
perception studies. The results demonstrate that unsupervised bottom-up
training on context-free acoustic information leads to comparable learned
representations of perceptual space between native and non-native conditions
for both English and Mandarin, resembling the early stage of universal
listening in infants. These findings provide insights into the organization of
perceptual space during early phonetic acquisition and contribute to our
understanding of the formation and representation of phonetic categories.
