Many techniques have been proposed for dealing with the various sorts of semantic ambiguities, ranging from psychologically motivated principles, to knowledge-based methods, heuristics, and statistical approaches. Psychologically motivated principles are exemplified by Quillian's spreading activation model (described earlier) and the use of selectional preferences in word sense disambiguation. For example, in  “The job took five hours,” took might be disambiguated to the sense of taking up time because that sense of the verb prefers a temporal complement, and job might be disambiguated to task (rather than, say, occupation) because of the direct associative link between the concept of a task and its time demands. Examples of knowledge-based disambiguation would be the disambiguation of ice sculpture to a constitutive relation based on the knowledge that sculptures may be carved or constructed from solid materials, or the disambiguation of a man with a hat to a wearing-relation based on the knowledge that a hat is normally worn on the head. (The possible meanings may first be narrowed down using heuristics concerning the limited types of relations typically indicated by nominal compounding or by with-modification.)  Heuristic principles used in scope disambiguation include island constraints (quantifiers such as every and most cannot expand their scope beyond their local clause) and differing wide-scoping tendencies for different quantifiers (e.g., each is apt to assume wider scope than some).  Statistical approaches typically extract various features in the vicinity of an ambiguous word or phrase that are thought to influence the choice to be made, and then make that choice with a classifier that has been trained on an annotated text corpus. The features used might be particular nearby words or their parts of speech or semantic categories, syntactic dependency relations, morphological features, etc..  Such techniques have the advantage of learnability and robustness, but ultimately will require supplementation with knowledge-based techniques. For example, the correct scoping of quantifiers in contrasting sentence pairs such as