What makes a sentence hard to process ? Apart from the meanings of the words it contains , their number , and the way these words combine into constituents , words also contribute to processing difficulty on the basis of their accessibility in lexical retrieval . Apart from their frequency of use or their complexity in form , accessibility is also influenced by the number and roles of the related forms in the paradigms in which they are stored . This is a factor that so far has not been sufficiently taken into account . As is experimentally shown in this dissertation , a measure for this is the inflectional entropy , an information - theoretic measure that quantifies the support that a word receives from its inflectional paradigm , during activation . This study investigates how the speed of sentence processing is modulated by the interaction of the linguistic - imposed constraints and the processing resources , as quantified by the inflectional entropy , within - and between - sentences and within - and between - languages . The experimental data indicate that the processing speed of a reflexive object , like the Dutch zichzelf , unlike a definite NP like Maria , depends on how the main verb is processed , providing evidence that the reflexiveâs interpretation requires an operation on the verb . Moreover , it is demonstrated that processing speed benefits from rich morphology . In fact , morphologically rich languages , like Greek , despite having longer words and more complicated paradigms , also have verbs with higher inflectional entropy than morphologically poor languages , like Dutch . As such , they require fewer processing resources during first activation , boosting computations that are costly .