Word learning biases are certain biases or assumptions that allow children to quickly rule out unlikely alternatives in order to effectively process and learn word meanings. They begin to manifest themselves around 18 months, when children begin to rapidly expand their vocabulary. These biases are important for children with limited processing abilities if they are to be successful in word learning. The guiding lexical principles have been defined as implicit and explicit strategies towards language acquisition. When a child learns a new word they must decide whether the word refers to the whole object, part of the object, its substance, color or texture. The following sources are used to solve this indeterminacy problem.
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Whole-object bias
Whole object bias, in developmental psychology, For example, if a child is shown and given the label "truck", the child will assume truck refers to the whole object instead of the tires, doors, colors or other parts. If a researcher points to an object while simultaneously saying a new name, children will assume that the new label refers to the whole object. Ellen Markman pioneered work in this field. Her studies suggest that even in cases where color or a dynamic activity are made salient to children, they will still interpret the new word as a label for whole objects. Furthermore, infants hold a primitive theory of the physical world that is guided by three constraints on the behavior of physical bodies: objects must move as wholes, objects move independently of each other, and objects move on connected paths. It is suggested that these three constraints help guide children’s interpretations of scenes, and, in turn, explains how the whole object bias reflects the nonlinguistic status of objects. Criticisms of the whole object bias highlight that evidence is only provided for children 18 months and older, a restricted set of stimuli has been used that possibly favors a “whole” interpretation, and finally, the whole object bias serves more as an explanation rather than a description. A more current study strengthened the breadth of ages and stimuli conditions under which this bias occurs. As early as 12 months of age infants can associate words with whole objects when the objects can be viewed as two separate objects and even when one of the parts is made salient. The whole object bias findings have been replicated with adults as well. Even when participants, 18–36 years of age, were instructed that they would be tested more frequently for parts, they were better able to recognize the whole objects rather than parts. These findings support the hypothesis that there is a bias to encode the overall shape of the stimuli in working memory rather than individual details. The whole object constraint can be overcome in order for children to learn the labels of parts, substances and other properties of objects. This is done through the mutual exclusivity bias, which makes the assumption that each object has only one label.
Mutual exclusivity bias
Children may be able to narrow the hypotheses down, but the mutual exclusivity (psychology) assumption cannot provide which alternative is correct. The advantage of this bias is that it helps children avoid making redundant guesses about the meanings of category terms. Children resist assigning a label to an object for which they already have a name or at least will not learn the new name as easily. Children are then able to start considering other possibilities for the new label, for instance, a part of the object. Markman and Wachtel’s 1988 studies demonstrated the learning process through the whole-object and mutual exclusivity assumption. The experimenter told three-year-old children a word and then showed them a picture. She asked whether the label referred to the whole object or a part and outlined each option with her finger. When the whole object was unfamiliar they pointed to the part in only 20% of the trials, but pointed to the part in 57% of the trials when the object was familiar. A more recent study attempted to replicate and extend these results. Hansen and Markman taught children a new word for a part of a real object by saying the word and tracing the object’s contours. (These gestures were meant to remain as naturalistic as possible). They then asked children to point to the new part in order to identify if they have linked the new name to the intended part. The main manipulation was whether the object was familiar or not. Upholding the mutual exclusivity bias children pointed to the intended part more often in the familiar object condition. Furthermore, the gesture of pointing/outlining the part itself was insufficient for children to learn the part name. Mutual exclusivity and a gesture were necessary for children to select the novel part. Other researchers have come up with similar principles. Clark’s contrast theory holds that “every two forms contrast in meaning”. When a new word is presented the child assumes it refers to something that does not yet have a label, but contrast does not take into account the overlap words may have in meaning. Golinkoff’s novel name-nameless category (N3C) also states that a child will map a new name to the unnamed object when a named object is present. Unlike contrast, N3C does not require children to understand synonymy, and unlike mutual exclusivity it does not hold that objects have only one name. Furthermore, this principle is not one of the first assumptions child learn mainly because, at this point, children are not dependent on an explicit link between the new word and the object (i.e. by pointing). By acquiring this principle the indirect link of seeing an unnamed object while hearing a new word is enough for the child to map the new label to the unnamed object.
Taxonomic constraint
Ordinarily, children focus on thematic relations between objects when categorizing. If given milk, a spoon, or a car, children will group each item with a cow, soup, or a stop sign, respectively. However, when children hear a new label they shift their attention to taxonomic relationships, even though they consider thematic relations to be a good way of organizing the objects themselves. Instead of cow being linked to milk it would be linked to pig or horse. The new word is assumed to refer to other objects within the same taxonomic category. Ellen Markman’s early work showed this constraint at work. When two- and three-year-olds were presented with two basic-level objects, two different kinds of dogs, and a third thematically related object, dog food, they showed a tendency to select a dog and dog food; however, if one of the dogs was labeled with an unfamiliar word, the children were more likely to select the two dogs. Another study conducted by Backscheider & Markman attempted to clarify whether this assumption was powerful enough to overcome the preference for thematic relations when objects are engaged in dynamic thematic relations at the time of labeling. A doll was repeatedly seated in a chair when the child either heard "see the bif" or "see this". The label, "bif", caused children to pick objects of the same kind, whereas, the absence of the label caused them to organize objects to the thematic event they had witnessed. Children use this assumption as early as 18 months of age. Similar to the taxonomic constraint researchers have looked into the principle of categorical scope, which also follows the assumption that children will believe new object labels refer to objects within taxonomic categories. An example of categorical scope and perceptual similarity can be illustrated when children learn animal names. Studies show that children think the identity of an animal only changes if its internal properties change. Children extended labels to two perceptually similar animals more often than when they were dissimilar. Furthermore, they were able to overcome mutual exclusivity in the process. In contrast to this assumption, research has sought to find out whether children hold an antithematic bias. The theory is such that children begin word learning by believing that new words do not label thematic categories, and simply choose taxonomic categories by default. One study gave children three items: a taxonomic, thematic, and neutral object, in order to test if the child avoided the thematic choice and preferred the taxonomic one to the neutral item. While four-year-olds did show this bias in new word extension, more research must be conducted to determine when the bias is established and how strongly it is held.