What is happening in our minds when we understand sentences?

When we read and understand sentences, what is happening in our minds? This is the central question in the study of sentence processing. We process sentences with remarkable speed and accuracy, but what allows us to do this so effortlessly? At first glance, it might seem straightforward: we identify the meaning of individual words, combine them, and arrive at the meaning of the sentence. However, formal linguistics studies have revealed that a sentence is much more than a simple string of words. Sentences have intricate, abstract, hierarchical structures that form the foundation of their meaning. To comprehend a sentence, our minds must construct this hidden structure in real-time.Researchers believe that understanding a sentence relies on recognizing grammatical relations, such as the subject, verb, and object. Analyzing words in a sentence is considered central to this process. But sentences with omitted/silent parts, known as ellipsis constructions, challenge this view. For example, consider the sentence: “John ate something, but I don’t know what.” Here, the part of the sentence after “what” is omitted. Thus there are no overt words that can signal the meaning and the structure of the sentence. Despite this missing information, we can easily and quickly understand the meaning of ellipsis sentences.How do we manage this? Some researchers have suggested that our minds bypass the need to build a detailed hierarchical structure. Instead, we rely on a simpler mechanism that allows us to “fill in the blanks” without recourse to underlying structures.Our recent study challenges this idea. We’ve found evidence that readers do, in fact, construct abstract hierarchical structures even when parts of a sentence are missing. When encountering the omitted portion, readers immediately refer to the non-omitted part of the sentence for clues about the missing structure. In other words, when we read sentences, our minds are not just recognizing words—they are rapidly constructing and analyzing the abstract structures behind them. Even when part of a sentence is missing, our mental “grammar engine” works behind the scenes to ensure we fully understand its meaning.