What phenomenon describes our tendency to fill in gaps in incomplete words?

The phenomenon that describes our tendency to fill in gaps in incomplete words is known as the phonemic restoration effect. This cognitive process occurs when listeners perceive missing sounds in speech and automatically fill in these gaps based on contextual information, memory, and their understanding of language. For instance, if a part of a word is obscured or missing due to noise or other interference, the brain uses context and linguistic cues to "restore" the missing segments, allowing for coherent understanding. This ability demonstrates how our perceptual system works to maintain communication even when the auditory input is not complete.

In contrast, the other concepts mentioned don't pertain to this specific aspect of speech perception. Speech rate normalization relates to how hearing can adapt to different speaking rates, categorical perception refers to the way we perceive speech sounds distinctly categorized rather than on a continuum, and vocal tract normalization involves adjusting for differences in how sounds are produced by different speakers. None of these concepts directly explain the cognitive process of completing words with missing sounds.