Learning Words Over Time: The Role of Stimulus Repetition in Mutual Exclusivity

Abstract

During the second year of life, infants develop a preference to attach novel labels to novel objects. This behavior is commonly known as “mutual exclusivity” (Markman, 1989). In an intermodal preferential looking experiment with 19.5- and 22.5-month-olds, stimulus repetition was critical for observing mutual exclusivity. On the first occasion that a novel label was presented with 1 familiar object and 1 novel object, looking behavior was unsystematic. However, on reexposure to the same stimuli, 22.5-month-olds looked preferentially at the novel object prior to the re-presentation of the novel label. These findings suggest a powerful memory mechanism for novel labels and objects, enabling mutual exclusivity to emerge across repeated exposures to potential referents.

Notes

¹For convenience the term mutual exclusivity will be used to refer to this behavior, although other explanations include the novel-name-nameless-category (N3C) principle (Mervis & Bertrand, 1994), feeling of novelty principle (Merriman, Marazita, & Jarvis, 1995), principle of contrast (Clark, 1993), and general forms of socio-pragmatic inference (e.g., Diesendruck & Markson, 2001).

²It is unclear whether infants in Halberda (2003) displayed a preference for the familiar object during the prenaming phase of a trial, because only difference scores between the pre- and postnaming phases of a trial are reported.

³Although the analyses reported include these 2 infants, the exclusion of the 2 infants from the analysis resulted in a similar pattern of findings.

⁴Further analyses with exclusionary criteria did not significantly alter the pattern of reported findings. The exclusion of trials for which infants were not reported as knowing the name of the familiar object resulted in a very similar pattern of effects at both ages. When the two 22.5-month-olds from homes with a second minority language were excluded, there remained a significant interaction between trial repetition, trial type, and trial phase (p < .015), a significant difference between the novel label and control repeat trials for the 1.5–3 sec (p < .005) and 3–4.5 sec (p < .05) trial phases, and attention to the novel object for the 1.5–3 sec trial phase of novel label repeat trials was significantly below chance (p < 05).

⁵We did not, however, find a familiar object preference on the control condition at 19.5 months of age. The robustness of the effect at this age might account for this discrepancy with Schafer et al. (1999) and White and Morgan (2008). For example, in White and Morgan, data were averaged over a longer sampling period and for a larger number of trials than for the individual trial phases in the control condition of this study.