The prevalence and the weakness of an early name mapping preference.

An empirical puzzle regarding toddlers' fast mapping motivated the current investigation. Whereas children between 1;10 and 2;1 have shown only a modest rate of mapping novel nouns onto unfamiliar rather than familiar objects, a very high rate has been observed in those between 1;4 and 1;8 (Mervis & Bertrand, 1991). Study 1 examined whether young two-year-olds (N = 40, mean age = 2;1) might map at a higher rate when tested with procedures unique to Mervis & Bertrand's assessment--strong corrective feedback rather than mild positive non-contingent feedback; large sets of test objects rather than pairs; presentation of easier tests first. Only the first variable affected performance in a manner that could solve the puzzle. Unfamiliar kinds were selected at a much higher rate under corrective (0.86) than non-contingent (0.57) feedback. Although nearly every child in the non-contingent group chose correctly on the first trial, many failed to do so thereafter. In Study 2, rather than presenting a test word to the children (N = 16, mean age = 2;2), the experimenter merely asked for 'the one I want'. Unfamiliar kinds were selected much less often than in Study 1, suggesting that at least one lexical principle proposed in the literature underlies the noun mapping preference. Changes over trials in the two studies indicated that the noun mapping preference is quite prevalent, but unless initial choices are strongly reinforced, an increase in the salience of familiar kinds after the first trial lures some children into error. Consistent with this analysis, toddlers in Study 3 (N = 24, mean age = 2:1) who received non-contingent strong acceptance for their noun mapping decisions, selected unfamiliar kinds more often than those who had received non-contingent mild acceptance in Study 1.

Restricting a familiar name in response to learning a new one: evidence for the mutual exclusivity bias in young two-year-olds.

Children under 2 1/2 years old tend to interpret novel words in accordance with the Mutual Exclusivity Principle, but tend not to reinterpret familiar words this way. Because alternative principles have been proposed that only predict the novel word effects, and because tests of the familiar word effects may have been flawed, a new test was administered. In Experiment 1 (N = 32), 24- to 25-month-olds heard stories in which a novel noun was used for an atypical exemplar of a familiar noun. When asked to select exemplars of the familiar noun, they showed a small but reliable tendency to avoid the object from the story. In Experiment 2 (N = 16), the novel nouns in the stories were replaced by pronouns and proper names, and the children did not avoid the story object in the test of the familiar noun. Thus, the aversion to this object that was observed in Experiment 1 was not due to its greater exposure or its being referenced immediately before testing, but to toddlers' Mutual Exclusivity bias. Their bias is hypothesized to be a form of implicit probabilistic knowledge that derives from the competitive nature of category retrieval.

Young two-year-olds' tendency to map novel verbs onto novel actions.

Children tend to select novel objects over familiar ones as the likely referents of novel nouns. This finding is of central importance to several accounts of early word learning. In the current studies, 2-year-olds were shown pairs of videotaped actions, one familiar and one novel, and were asked to select the referents of novel verbs. For actions that did not involve objects, children tended to select the novel action over the familiar one in each of four experiments. For example, they chose the woman who was turning in circles while leaning backwards as "the one who is glarving" more often than the woman who was running. For actions involving objects, novel actions (e.g., shuffling balls) were chosen more often than familiar ones (e.g., kicking balls) in only two of the four experiments. An object-name-blocking mechanism was proposed to account for this last result. The preference for novel actions was also found to be strengthened by preexposing both actions from a test pair, but to be unaffected by preexposing just the novel actions.

What can be learned from something's not being named.

A new word-learning phenomenon is demonstrated and a new word-learning principle is proposed to account for it. In Study 1, 60 3-year-olds were shown a pair of objects and heard a novel label used repeatedly for one, but not for the other. In a forced-choice test of generalization of the label, the latter object was selected less often by the children than one that had not been present during training. This so-called Nominal Passover Effect was the same whether the speaker had completely ignored the comparison object during training or had referred to it with pronouns. The performance of a no-word control group (N = 24) indicated that the effect was not due to a preference for the less exposed of the two choice objects. The effect is consistent with the Exhaustive Reference Principle, which stipulates that whenever a new generic word is used to name something, expect it to be extended to all entities in a situation that the speaker perceives and believes to be exemplars of the name. In Study 2 (N = 48), the Nominal Passover Effect was replicated with 3 new sets of objects and with training language that contained only indefinite forms of reference. The passover experience was often sufficient to counteract children's tendency to generalize a novel label on the basis of perceptual similarity. The passover effect was not evident in free-choice name generalization tests in either study.

How shall a deceptive thing be called?

Thirty-six three-, four- and five-year-olds were asked to select labels for deceptive stimuli (e.g. for an eraser that looked like a pencil). Three types of labelling were investigated--simple (e.g. 'is an eraser'); appearance-predicated (e.g. 'looks like an eraser'); and reality-predicated (e.g. 'is really and truly an eraser'). An age-related appearance--reality shift was observed in simple labelling (e.g. older children were more likely than younger ones to accept eraser and reject pencil as simple names for the pencil-eraser). This trend was robust over method and semantic domain, though weaker with object than with colour labels. As in previous research, older children were more likely than younger ones to map different appearance- than reality-predicated labels onto an item (e.g. to accept that the pencil-eraser looks like a pencil, but is really and truly an eraser); however, all age groups were reluctant to extend more than one name to a stimulus via a common predicate (e.g. to accept two reality-predicated labels for the same object). This one-label-perpredicate pattern was observed more frequently within reality than within appearance predicates; more frequently with colour than with object names, and with questions blocked by predicate than by name. It is argued that younger children maintained this pattern because of inflexible encoding, but that older ones did so because of better understanding of the appearance-reality distinction, greater reality dominance, and a Mutual Exclusivity bias.

Four-year-olds' disambiguation of action and object word reference.

Preschool-age children show a very strong tendency to map a novel noun onto an unfamiliar rather than a familiar object. This so-called disambiguation effect has been interpreted as evidence that youngers expect object labels to be mutually exclusive. In Experiment 1, 4-year-olds were observed to map a novel verb onto an unfamiliar action about twice as often as they mapped it onto a familiar one. When the unfamiliar action had been preexposed, but the familiar one had not, the mapping preference was eliminated. In Experiment 2, 4-year-olds mapped a novel noun onto an unfamiliar object about five times as often as they mapped it onto a familiar object, and this tendency was not affected by preexposure. Even when action embedding and question complexity were controlled, the disambiguation effect was stronger for object than for action words. An account is presented in which two lexical principles, Mutual Exclusivity and Feeling of Novelty, are hypothesized to apply differently to action than to object words.

An appearance-function shift in children's object naming.

The relative importance of appearance and potential function in children's object naming was examined. Potential function is an object capability that may not be currently realized (e.g. an empty mug has the potential to hold coffee). In Study 1, sixteen children from each of three age groups (3;8, 4;8, and 6;1) were taught novel names for unfamiliar objects; they then had to decide whether these applied to items that resembled the training objects in either appearance or potential function. The youngsters were also shown deceptive objects (e.g., an eraser that looked like a pencil) and had to choose between familiar appearance and function names for them (e.g., pencil or eraser). The frequency of function-based responding in both tasks increased with age. In Study 2, the name training procedure was revised so that equal emphasis was given to both apparent and functional features. The main results of the first study were replicated. Neither study obtained evidence of a strong relation between the appearance-function shift and increased understanding of the appearance-reality distinction.

Young children's disambiguation of object name reference.

Children show a disambiguation effect--a tendency to select unfamiliar rather than familiar things as the referents of new names. In previous studies, this effect has been reversed in young 2-year-olds, but not older children, by preexposing the unfamiliar objects, suggesting that attraction to novelty controls 2-years-olds' choices of referents for new names, but a mutual exclusivity and/or lexical gap-filling principle determines preschoolers' selections. Both the disambiguation effect and its reversal by preexposure were replicated in the present study; however, 24-month-olds' rate of selecting unfamiliar over familiar kinds was less when they were simply asked to choose between the items than when they were asked to identify the referents of unfamiliar names. Thus, some young children may have both an attraction to novel tokens and a tendency to honor an abstract lexical principle. Referent selections were also affected by object typicality and word similarity. Correlations between the tendency to acknowledge a new name's unfamiliarity and to treat it like a similar-sounding familiar name suggested that youngsters' phonological matching skills affect their interpretation of new names. Also, 4-year-olds who most often mapped distinctive-sounding new names to unfamiliar kinds tended to admit their unfamiliarity with these names most frequently, suggesting that children's increasing awareness of their own knowledge begins to affect their lexical processing during the preschool years.

Are names ever mapped onto preexisting categories?

Support for Mervis's (1987) proposal that youngsters map new common nouns onto attribute cluster categories was obtained. In 3 studies, preschoolers interpreted a novel noun as if it designated a preexposed category. Experiment 3 included a group of adults who behaved similarly. Mapping was independent of the tendency to generalize according to shape. Neither age group mapped onto preexisting categories when making object similarity judgments, but preexposure did bias their naming of the objects' colors. Those who had examined sets containing 2 colors, both of which covaried with other bivalent dimensions, used more distinctive names for these hues than those preexposed to sets containing 6 colors, none of which covaried with bivalent dimensions.

The mutual exclusivity bias in children's word learning.

Nearly every recent account of children's word learning has addressed the claim that children are biased to construct mutually exclusive extensions, that is, that they are disposed to keep the set of referents of one word from overlapping with those of others. Three basic positions have been taken--that children have the bias when they first start to learn words, that they never have it, and that they acquire it during early childhood. A review of diary and test evidence as well as the results of four experiments provide strong support for this last view and indicate that the bias develops in the months following the second birthday but does not gain full strength or become accessible to consciousness until sometime after the third birthday. Several studies also show that, after this point, it can still be counteracted by information in input or by a strong belief that something belongs to the extension of a particular word. The full body of evidence is compatible with the view that mutual exclusivity is the default option in children's and adults' procedures for integrating the extensions of new and old words. We present several arguments for the adaptive value of this kind of bias.

A life-span study of the interaction of selectivity and knowledge in memory.

Preschool children, young adults, and old adults viewed a series of familiar scenes and were asked to remember 1 item from each. The incidental memory of both children and old adults was less accurate than that of young adults. The result for children contrasts with the typical result of selective memorization research. Memory for high-expectancy items exceeded that for low-expectancy items by a greater margin when items were incidental, suggesting that even preschool children activate scene schemas during encoding. Only the young adults, however, showed the predicted tendency to recognize low-expectancy items better than high-expectancy items when items were intentional. These results may be reconcilable if some, but not all, schema-mediated encoding effects on memory depend on strategic encoding.

Differences in memory retrieval: a construct validity investigation.

Long-term memory retrieval efficiency was investigated as a potential underlying source of individual and developmental differences in cognitive functioning. Fourth-grade, eighth-grade, and college-aged subjects participated in a task using the Posner letter-matching paradigm. Letter pairs were presented simultaneously under physical-match and name-match instruction conditions. Reaction times were used to estimate parameters of long-term memory retrieval efficiency, basic encoding, decision, and response time, and name and physical output interference. Psychometric tests of verbal and spatial ability were included to assess convergent and discriminant validity of hypothesized relationships between aptitude test performance and basic cognitive processes. Developmental differences were observed in most but not all of the processing variables. Individual difference analyses indicated that less confounded estimates of processing parameters were not systematically related to verbal ability at any age level. Basic encoding and response speed was the most consistent correlate of spatial ability. The results suggest difficulties in previous interpretations of NIPI-verbal ability relationships. The study of cognitive processes in interaction and embedded in meaningful tasks is discussed.