This study examined whether 12-month-olds will accept words that differ phonologically and phonetically from their native language as object labels in an associative learning task. Sixty infants were presented with sets of English word-object (N = 30), Japanese word-object (N = 15), or Czech word-object (N = 15) pairings until they habituated. Infants associated CVCV English, CCVC English, and CVCV Japanese words, but not CCVC Czech words, with novel objects. These results demonstrate that by 12 months of age, infants are beginning to apply their language-specific knowledge to their acceptance of word forms. That is, they will not map words that violate the phonotactics of their native language to objects.

We examined whether 12-month-old infants privilege words over other linguistic stimuli in an associative learning task. Sixty-four infants were presented with sets of either word–object, communicative sound–object, or consonantal sound–object pairings until they habituated. They were then tested on a ‘switch’ in the sound to determine whether they were able to associate the word and/or sound with the novel objects. Infants associated words, but not communicative sounds or consonantal sounds, with novel objects. The results demonstrate that infants exhibit a preference for words over other linguistic stimuli in an associative word learning task. This suggests that by 12 months of age, infants have developed knowledge about the nature of an appropriate sound form for an object label and will privilege this form as an object label.

A fundamental step in learning words is the development of an association between a sound pattern and an element in the environment. Here we explore the nature of this associative ability in 12-month-olds, examining whether it is constrained to privilege particular word forms over others. Forty-eight infants were presented with sets of novel English content-like word-object pairings (e.g. fep) or novel English function-like word-object (e.g. iv) pairings until they habituated. Results indicated that infants associated novel content-like words, but not the novel function-like words, with novel objects. These results demonstrate that the mechanism with which basic word-object associations are formed is remarkably sophisticated by the onset of productive language. That is, mere associative pairings are not sufficient to form mappings. Rather the system requires well-formed noun-like words to co-occur with objects in order for the linkages to arise.

We explored 12-month-olds' flexibility in accepting phonotactically illegal or ill-formed word forms in a modified associative-learning task. Sixty-four English-learning infants were presented with a training phase that either clarified the purpose of a sound-object association task or left the task ambiguous. Infants were then habituated to sets of Czech words with onsets that are illegal in English (e.g., ptak), consonantal sounds (e.g., /l/), or novel functionlike words (e.g., iv). When infants were provided with a training phase that highlighted the purpose of the task, they associated the phonotactically illegal Czech words, but not the consonantal sounds or novel functionlike words, with objects. Thus, English-learning 12-month-old infants' flexibility in associating various sound forms with novel objects is limited to labels that share the structural shape of well-formed nounlike words.

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This empirically derived difficulty-level system created for storybooks read aloud to preschoolers represents a step toward filling a gap in the read-aloud literature.

One way to minimize excitation acquired by the conditioned stimulus (CS) is to introduce intertrial presentations of the unconditioned stimulus (US). However, even in the presence of frequent intertrial USs, Experiments 1a and 1b found that rats anticipated the customary arrival time of a food pellet US when it occurred before (embedded)-versus coincident with (delay)-the termination of a white noise CS. Delay conditioning emerged in Experiment 2 in the absence of intertrial USs; hence, the detrimental effects of intertrial USs depended on the CS-US relationship, delay versus embedded, and not the duration of CS-US interval. Experiments 3a, 3b, and 4 found that random USs located in the early portion of the intertrial interval increased the control acquired by contextual stimuli at the expense of temporal stimuli occasioned near CS termination. Our results suggest that delay relationships leave the CS especially vulnerable to the deleterious effects of intertrial USs.

We examined if and when English-learning 17-month-olds would accommodate Japanese forms as labels for novel objects. In Experiment 1, infants (n = 22) who were habituated to Japanese word–object pairs looked longer at switched test pairs than familiar test pairs, suggesting that they had mapped Japanese word forms to objects. In Experiments 2 (n = 44) and 3 (n = 22), infants were presented with a spoken passage prior to habituation to assess whether experience with a different language would shift their perception of Japanese word forms. Here, infants did not demonstrate learning of Japanese word–object pairs. These findings offer insight into the flexibility of the developing perceptual system. That is, when there is no evidence to the contrary, 17-month-olds will accommodate forms that vary from their typical input but will efficiently constrain their perception when cued to the fact that they are not listening to their native language.