Four experiments assessed visual short-term memory capacity in 4- to 13-month-old infants by comparing their looking to changing and nonchanging stimulus streams presented side by side. In each stream, 1 to 6 colored squares repeatedly appeared and disappeared. In changing streams, the color of a different randomly chosen square changed each time the display reappeared; the colors remained the same in nonchanging streams. Infants should look longer at changing streams, but only if they can remember the colors of the squares. The youngest infants preferred changing streams only when the displays contained one object, whereas older infants preferred changing streams when the displays contained up to 4 objects. Thus, visual short-term memory capacity increases significantly across the first year of life.

No abstract

No abstract

The binding of object identity (color) and location in visual short-term memory (VSTM) was examined in 6.5- to 12.5-month-old infants (N= 144). Although we previously found that by age 6.5 months, infants can represent both color and location in VSTM, in the present study we observed that 6.5-month-old infants could not remember trivially simple color-location combinations across a 300-ms delay. However, 7.5-month-old infants could bind color and location as effectively as 12.5-month-old infants. Control conditions confirmed that the failure of 6.5-month-old infants was not a result of perceptual or attentional limitations. This rapid development of VSTM binding between 6.5 and 7.5 months occurs during a period of rapid increase in VSTM storage capacity and just after a period of dramatic neuroanatomical changes in parietal cortex. Thus, the ability to bind features and the ability to store multiple objects may both depend on a process that is mediated by posterior parietal cortex and is perhaps related to focused attention.

Three experiments directly compared infants' categorization in variations of the visual familiarization task. In each experiment, 4‐ or 6‐month‐old infants were familiarized with a collection of dogs or cats and then their response to novel dogs and cats was assessed. In Experiment 1, 4‐month‐old infants responded to the exclusive distinction of dogs or cats when tested in a paired‐comparison task. In Experiments 2 and 3, 6‐month‐old infants, but not 4‐month‐old infants, responded to this same distinction in a successive presentation task, even when the amount of familiarization was equated to that of the paired comparison task. Therefore, familiarization with a particular set of stimuli does not induce infants to respond to a single category but rather they respond to different categories depending on features of the task.

Habituation of looking time has become the standard method for studying cognitive processes in infancy. This method has a long history and derives from the study of memory and habituation itself. Often, however, it is not clear how researchers make decisions about how to implement habituation as a tool to study processes such as categorization, object representation, and memory. This article describes the challenges for implementing this tool, and describes a set of best practices for its use to study perception and cognition in infancy.

Infant research is hard. It is difficult, expensive, and time consuming to identify, recruit and test infants. As a result, ours is a field of small sample sizes. Many studies using infant looking time as a measure have samples of 8 to 12 infants per cell, and studies with more than 24 infants per cell are uncommon. This paper examines the effect of such sample sizes on statistical power and the conclusions drawn from infant looking time research. An examination of the state of the current literature suggests that most published looking time studies have low power, which leads in the long run to an increase in both false positive and false negative results. Three data sets with large samples (>30 infants) were used to simulate experiments with smaller sample sizes; 1000 random subsamples of 8, 12, 16, 20, and 24 infants from the overall samples were selected, making it possible to examine the systematic effect of sample size on the results. This approach revealed that despite clear results with the original large samples, the results with smaller subsamples were highly variable, yielding both false positive and false negative outcomes. Finally, a number of emerging possible solutions are discussed.

Two experiments investigated the role of continuity cues in infants' perception of launching events as causal. Experiment 1 showed that 7-month-old infants can use spatial and temporal contiguity to perceive causality: Infants who were habituated to a causal event dishabituated to novel noncausal events, in which either spatial or temporal contiguity was violated, and those who were habituated to a noncausal event dishabituated to a novel causal but not a novel noncausal event. Experiment 2 showed that 10-month-olds, but not 7-month-olds, perceived the causality of launching events in which the objects moved along dissimilar paths. Thus, younger infants do not appear to attend to causality when the objects move along different paths. Results are discussed in terms of the development of the use of continuity cues in causal judgments.