Susan J. Hespos

Do infants understand simple arithmetic? A replication of Wynn (1992) ☆

Abstract Numerical competence in 5-month-old infants is investigated using a violation-of-expectation paradigm. An experiment is reported which replicates the findings of Wynn (1992). In additional conditions, 5-month-olds are shown to be sensitive to impossible outcomes following addition or subtraction operations on small sets of objects, regardless of identity changes. Results support Wynns interpretation that infants responses are based on arithmetical ability. An alternative explanation, that infants responses are based on their knowledge of the principles of physical object behavior, is also discussed.

Conceptual precursors to language

Because human languages vary in sound and meaning, children must learn which distinctions their language uses. For speech perception, this learning is selective: initially infants are sensitive to most acoustic distinctions used in any language, and this sensitivity reflects basic properties of the auditory system rather than mechanisms specific to language; however, infants sensitivity to non-native sound distinctions declines over the course of the first year. Here we ask whether a similar process governs learning of word meanings. We investigated the sensitivity of 5-month-old infants in an English-speaking environment to a conceptual distinction that is marked in Korean but not English; that is, the distinction between ‘tight’ and ‘loose’ fit of one object to another. Like adult Korean speakers but unlike adult English speakers, these infants detected this distinction and divided a continuum of motion-into-contact actions into tight- and loose-fit categories. Infants sensitivity to this distinction is linked to representations of object mechanics that are shared by non-human animals. Language learning therefore seems to develop by linking linguistic forms to universal, pre-existing representations of sound and meaning.

Infants' Knowledge About Occlusion and Containment Events: A Surprising Discrepancy

The present research examined whether infants acquire general principles or more specific rules when learning about physical events. Experiments 1 and 2 investigated 4.5-month-old infants ability to judge how much of a tall object should be hidden when lowered behind an occluder versus inside a container. The results indicated that at this age infants are able to reason about height in occlusion but not containment events. Experiment 3 showed that this latter ability does not emerge until about 7.5 months of age. The marked discrepancy in infants reasoning about height in occlusion and containment events suggests that infants sort events into distinct categories, and acquire separate rules for each category.

Differential rooting response by neonates: Evidence for an early sense of self

It is proposed that from birth, and long before mirror self-recognition, infants manifest a sense of self as a differentiated and situated entity in the environment. In support of this view, observations are reported suggesting that neonates discriminate between external and self-stimulation. Five newborns and 11 4-week-old infants were observed when they spontaneously brought one hand to their face, touching one of their cheeks (self-stimulation), or when the index finger of the experimenter touched one of the infants cheeks (external stimulation). Microanalysis revealed that infants responded differentially to the two types of stimulation. Newborns tended to display significantly more rooting responses (i.e., head turn towards the stimulation with mouth open and tonguing) following external compared to self-stimulation. Four-week-old infants demonstrated an opposite pattern. These data are discussed as evidence of an innate ability to discriminate between self versus externally caused stimulation. The differential expression of this ability at birth and at 4 weeks is considered in relation to learning opportunities and the emergence of new functional goals guiding infant behaviour. ©1997 John Wiley & Sons, Ltd.

Categorization in 3- and 4-Month-Old Infants: An Advantage of Words Over Tones

Neonates prefer human speech to other nonlinguistic auditory stimuli. However, it remains an open question whether there are any conceptual consequences of words on object categorization in infants younger than 6 months. The current study examined the influence of words and tones on object categorization in forty-six 3- to 4-month-old infants. Infants were familiarized to different exemplars of a category accompanied by either a labeling phrase or a tone sequence. In test, infants viewed novel category and new within-category exemplars. Infants who heard labeling phrases provided evidence of categorization at test while infants who heard tone sequences did not, suggesting that infants as young as 3 months of age treat words and tones differently vis-à-vis object categorization.

Reasoning about containment events in very young infants

The present research examined very young infants expectations about containment events. In Experiment 1, 3.5-month-old infants saw a test event in which an object was lowered inside a container with either a wide opening (open-container condition) or no opening (closed-container condition) in its top surface. The infants looked reliably longer at the closed- than at the open-container test event. These and baseline data suggested that the infants recognized that the object could be lowered inside the container with the open but not the closed top. In Experiment 2, 3.5-month-old infants saw a test event in which an object was lowered either behind (behind-container condition) or inside (inside-container condition) a container; next, the container was moved forward and to the side, revealing the object behind it. The infants looked reliably longer at the inside- than at the behind-container test event. These and baseline results suggested that the infants in the inside-container condition realized that the object could not pass through the back wall of the container and hence should have moved with it to its new location. Experiments 3 and 4 extended the results of Experiments 1 and 2 to 2.5-month-old infants. Together, the present results indicate that even very young infants possess expectations about containment events. The possible origins and development of these expectations are discussed in the context of Baillargeons model (Advances in infancy research 9 (1995) 305. Norwood, NJ: Ablex) of infants acquisition of physical knowledge, and of Spelkes proposal (Cognition 50 (1994) 431) that, from birth, infants interpret physical events in accord with a solidity principle.

Decalage in infants' knowledge about occlusion and containment events: converging evidence from action tasks.

In the present research, 6-month-old infants consistently searched for a tall toy behind a tall as opposed to a short occluder. However, when the same toy was hidden inside a tall or a short container, only older, 7.5-month-old infants searched for the tall toy inside the tall container. These and control results (1) confirm previous violation-of-expectation (VOE) findings of a décalage in infants reasoning about height information in occlusion and containment events; (2) cast doubt on the suggestion that VOE tasks overestimate infants cognitive abilities; and (3) support recent proposals that infants use their physical knowledge to guide their actions when task demands do not overwhelm their limited processing resources.

Dynamic mental representation in infancy

Recent research indicates that 4- to 8-month-old infants can track and anticipate the final orientation of an object following different invisible spatial transformations (Rochat, P., Hespos, S.J. (1996). Cognitive Development, 11, 3-17). Six experiments were designed to specify further the nature and development of early expectation for a set of dynamic events. A violation of expectation method was used to assess infants reactions to probable and improbable outcomes of an objects orientation following an invisible transformation. The availability of orientation cues, the path of motion, and the amount of invisible spatial transformation was systematically varied. The studies indicate that infants as young as 4 months of age detect orientation-specific cues for objects undergoing invisible spatial transformations. Developmental differences in this ability between 4 and 6 months of age lend insight to the nature and limitations of this early representational ability. These findings provide evidence for dynamic mental representation in infancy.

Tracking and anticipation of invisible spatial transformations by 4- to 8-month-old infants

Abstract The ability of 4- to 8-month-old infants to track and anticipate the final orientation of an object following different invisible spatial transformations was tested. A violation-of-expectation method was used to assess infants reaction to possible and impossible outcomes of an objects orientation after it translated or rotated behind an occluder. Results of a first experiment show that at all ages infants tend to look significantly longer at an impossible orientation outcome following invisible transformations. These results suggest that from 4 months of age, infants have the ability to detect orientation-specific information about an object undergoing linear or curvilinear invisible spatial transformations. A second experiment controlling for perceptual cues that infants might have used in the first experiment to track the object orientation replicates the results with a new sample of 4- and 6-month-old infants. Finally, a control experiment involving no motion yielded negative results, providing further support that infants as young as 4 months old use motion information to mentally track invisible spatial transformations. The results obtained in the rotation condition of both experiments are tentatively interpreted as providing first evidence of some rudiments of mental rotation in infancy.

Five-Month-Old Infants Have Different Expectations for Solids and Liquids

Many studies have established that 2-month-old infants have knowledge of solid objects basic physical properties. Evidence about infants understanding of nonsolid substances, however, is relatively sparse and equivocal. We present two experiments demonstrating that 5-month-old infants have distinct expectations for how solids and liquids behave. Experiment 1 showed that infants use the motion cues from the surface of a contained liquid or solid to predict whether it will pour or tumble from a cup if the cup is upended. Experiment 2 extended these findings to show that motion cues lead to distinct expectations about whether a new object will pass through or remain on top of a substance. Together, these experiments demonstrate that 5-month-old infants are able to use movement cues and solidity to discriminate a liquid from an object of similar appearance, providing the earliest evidence that infants can reason about nonsolid substances.