Sentence processing research examines how the parser — the cognitive system responsible for syntactic analysis — operates in real time. Since sentences unfold word by word, the parser must build structural interpretations incrementally, often before disambiguating information is available. How it handles this ambiguity, and what happens when its initial analysis proves wrong, are central questions in psycholinguistics.
Key Structures
- Broca's area (left inferior frontal gyrus) — The left inferior frontal region critical for speech production, syntactic processing, and verbal working memory, particularly in relation to left inferior frontal gyrus.
- Superior temporal gyrus — The upper temporal lobe gyrus containing auditory cortex and regions critical for speech perception and social cognition.
- Angular gyrus — A parietal region at the junction of temporal and parietal lobes, involved in semantic processing, reading, and number cognition.
- Eye — The sensory organ for vision, whose optical components focus light onto the retina for neural transduction.
Key Functions
Parse the grammatical structure of sentences in real time to assign syntactic roles and compute sentence meaning.
Garden-Path Sentences
Garden-path sentences (e.g., "The horse raced past the barn fell") initially lead the parser down an incorrect analysis that must be revised when contradicting information arrives. The difficulty readers experience at the disambiguating word ("fell") reveals the parser's initial commitment to a particular structure. Frazier's garden-path model proposed that the parser initially pursues the simplest structure (minimal attachment, late closure) and reanalyzes only when this fails.
Constraint-Based Models
Constraint-based models (MacDonald, Pearlmutter, Seidenberg) propose that the parser simultaneously considers multiple analyses weighted by all available constraints: word frequency, semantic plausibility, discourse context, and subcategorization preferences. Rather than committing to a single analysis, the system maintains a ranked set of alternatives. Ambiguity resolution involves the convergence of multiple probabilistic constraints rather than serial commitment and reanalysis.
Eye tracking has become the primary method for studying real-time sentence processing. Readers fixate longer on words that are syntactically ambiguous, semantically unexpected, or structurally complex. Regression eye movements (looking back to earlier words) indicate processing difficulty and reanalysis. The millisecond resolution of eye tracking reveals that syntactic, semantic, and discourse information all influence processing within the first fixation on a word.
Disorders
- Agrammatic aphasia — An aphasia subtype characterized by simplified sentence structure, omission of function words, and impaired syntactic processing.
- Specific language impairment — Significant language learning difficulties in children with normal hearing, intelligence, and no neurological damage.
- Syntactic deficits in Parkinson's disease