Exogenous attention influences visual short-term memory in infants

Two experiments examined the hypothesis that developing visual attentional mechanisms influence infants' Visual Short-Term Memory (VSTM) in the context of multiple items. Five- and 10-month-old infants (N = 76) received a change detection task in which arrays of three differently colored squares appeared and disappeared. On each trial one square changed color and one square was cued; sometimes the cued item was the changing item, and sometimes the changing item was not the cued item. Ten-month-old infants exhibited enhanced memory for the cued item when the cue was a spatial pre-cue (Experiment 1) and 5-month-old infants exhibited enhanced memory for the cued item when the cue was relative motion (Experiment 2). These results demonstrate for the first time that infants younger than 6 months can encode information in VSTM about individual items in multiple-object arrays, and that attention-directing cues influence both perceptual and VSTM encoding of stimuli in infants as in adults.     

Discrimination between solid forms in early infancy

This paper describes three experiments concerned with the ability of 3-month-old infants to discriminate between stationary solid forms. Experiment 1 confirmed, using a habituation/recovery technique, the finding of Cook, Field, and Griffiths (1978) that the infants do not distinguish between a cube and a truncated pyramid (and a range of other solid forms). Experiment 2 showed that infants can distinguish the square face of the cube from a trapezoidal face of the truncated pyramid when these shapes are presented in isolation. Experiment 3 showed that this discrimination is not made when the corresponding faces (square and trapezoid) of the solid cube and trapezoid are colored distinctively. These results are discussed in terms of limitations in the infants' capacity to resolve solid form.     

Infants' sensitivity to differential luminance as information about depth

To what degree are young infants able to perceive differential shadowing and to what degree are they able to utilize this stimulus parameter as information about depth? Two habituation experiments were performed. In Experiment 1, a group of 5-month-old infants were habituated to a low frequency, vertical, and approximately sinusoidal luminance grating superimposed on a flat colored surface. This display induced stable 3-D perception in adult subjects. After habituation, the infants viewed two test displays at alternating trials. One was made up of real half cylinders matching the light distribution of the habituation display and the other was made up of a square wave grating of the same spatial frequency as in the habituation one. Adults perceived the latter display as flat. Results showed that both test displays were treated as new ones by the infants habituated to the sinusoidal grating. Experiment 2 was identical to Experiment 1, except that the subjects were 3 1/2-month-old. These infants treated the half cylinders as familiar and the square wave grating as new. The results indicate that infants at both age levels (3 1/2 and 5 months of age) were sensitive to the difference between sharp and gradual change in luminance which is a prerequisite for perceiving form from luminance. However, neither age group seemed to utilize gradual change in luminance as information about space.     

Memory for multiple visual ensembles in infancy

The number of individual items that can be maintained in working memory is limited. One solution to this problem is to store representations of ensembles that contain summary information about large numbers of items (e.g., the approximate number or cumulative area of a group of many items). Here we explored the developmental origins of ensemble representations by asking whether infants represent ensembles and, if so, how many at one time. We habituated 9-month-old infants to arrays containing 2, 3, or 4 spatially intermixed colored subsets of dots, then asked whether they detected a numerical change to one of the subsets or to the superset of all dots. Experiment Series 1 showed that infants detected a numerical change to 1 of the subsets when the array contained 2 subsets but not 3 or 4 subsets. Experiment Series 2 showed that infants detected a change to the superset of all dots no matter how many subsets were presented. Experiment 3 showed that infants represented both the approximate number and the cumulative surface area of these ensembles. Our results suggest that infants, like adults (Halberda, Sires, & Feigenson, 2006), can store quantitative information about 2 subsets plus the superset: a total of 3 ensembles. This converges with the known limit on the number of individual objects infants and adults can store and suggests that, throughout development, an ensemble functions much like an individual object for working memory.     

Perception of internal elements of compound figures by one-month-old infants

Previous research has shown that infants younger than 2 months frequently concentrate their attention on peripheral or external features of visual stimuli and that they do not appear to process the internal elements of a compound visual stimulus composed of a simple geometric figure enclosed in a larger figure. A visual habituation-dishabituation paradigm was used to determine whether 1-month-old infants would process internal information if the internal elements of the stimulus were patterns often found to be preferred by young infants. Four groups of eight infants each were habituated to a compound stimulus consisting of a square or triangle surrounding a checkerboard or bull's-eye. Following habituation each group was presented with one of four types of stimulus: the identical stimulus (control group), a stimulus differing only in the internal component, a stimulus differing only in the external component, or a stimulus differing in both components. The results of the present study suggest that when the internal element of a compound stimulus is a highly preferred or salient stimulus, the young infant will process information about its characteristics.     

The importance of "what": Infants use featural information to index events

Dynamic spatial indexing is the ability to encode, remember, and track the location of complex events. For example, in a previous study, 6-month-old infants were familiarized to a toy making a particular sound in a particular location, and later they fixated that empty location when they heard the sound presented alone (Journal of Experimental Psychology: General, 2004, Vol. 133, pp. 46-62). The basis and developmental trajectory of this ability are currently unclear. We investigated dynamic spatial indexing across the first year after birth and tested the hypothesis that the structure of visual cues supports infants' learning of sound and location associations. In our study, 3-, 6-, and 10-month-olds were tested in a dynamic spatial indexing eye movement paradigm that paired two sounds with two locations. In one condition, these were reliably paired with two sets of visual features (two toys condition), replicating the original studies. We also presented a single set of visual cues in both locations (one toy condition) and multiple sets of visual features in both locations (six toys condition). Infants from 3months of age onward showed evidence of dynamic spatial indexing in the two toys condition, but only the 10-month-olds succeeded in the one toy and six toys conditions. We argue that this may reflect a broader developmental trajectory, whereby infants first make use of multiple cue integration but with age are able to learn from a narrow set of cues.     

Infants’ discrimination of crossed and uncrossed horizontal disparity

In a series of preferential-looking experiments, infants 5 to 6 months of age were tested for their responsiveness to crossed and uncrossed horizontal disparity. In Experiments 1 and 2, infants were presented with dynamic random dot stereograms displaying a square target defined by either a 0.5° crossed or a 0.5° uncrossed horizontal disparity and a square control target defined by a 0.5° vertical disparity. In Experiment 3, infants were presented with the crossed and the uncrossed horizontal disparity targets used in Experiments 1 and 2. According to the results, the participants looked more often at the crossed (Experiment 1), as well as the uncrossed (Experiment 2), horizontal disparity targets than at the vertical disparity target. These results suggest that the infants were sensitive to both crossed and uncrossed horizontal disparity information. Moreover, the participants exhibited a natural visual preference for the crossed over the uncrossed horizontal disparity (Experiment 3). Since prior research established natural looking and reaching preferences for the (apparently) nearer of two objects, this finding is consistent with the hypothesis that the infants were able to extract the depth relations specified by crossed (near) and uncrossed (far) horizontal disparity.     

Combinatorics and probability: six- to ten-year-olds reliably predict whether a relation will occur

Young children are able to judge which of two possibilities is more likely to occur when these possibilities are characterized by a simple property, like color (“Is it more likely to draw a red chip or a blue chip?”). Here we ask whether they can do so when the possibilities concern a relation between simple properties (“Is it more likely to draw two chips of the same color or two different colored chips?”). Three studies show that from the age of six children are able to predict the occurrence of a relation on the basis of its probability, and that from the age of nine their performance reaches adult levels. These results corroborate the theory of naive extensional reasoning, and are inconsistent with the hypothesis that children need the help of instruction to reason correctly about relations.     

Rapid eye movement (REM) in premature neonates and developmental outcome at 6 months

Different aspects of early sleep organization have been associated with subsequent development in premature infants. The aim of the present study was to assess the relations between rapid eye movement (REM) activity in premature neonates and infants' developmental outcomes at 6 months. Participants were 81 premature infants (47 males). Sleep-wake states and REM were observed across 4 consecutive evening hours (7-11 PM) in 10-s frames when infants were between 32 and 36 weeks post-menstrual age. Developmental outcome was assessed at 6 months with the mental development index (MDI) of the Bayley II. Infants with low-REM activity spent more time in less growth-promoting states, including crying and unfocused alert states in the neonatal period and had lower MDI scores at 6 months corrected age compared to infants with high-REM. Differences between the high- and low-REM groups were independent of neonatal medical risk. Low-REM activity may serve as an indicator of developmental risk among premature neonates.     

Perceiving an object and its context in different cultures: a cultural look at new look

Abstract - In two studies, a newly devised test (framed-line test) was used to examine the hypothesis that individuals engaging in Asian cultures are more capable of incorporating contextual information and those engaging in North American cultures are more capable of ignoring contextual information. On each trial, participants were presented with a square frame, within which was printed a vertical line. Participants were then shown another square frame of the same or different size and asked to draw a line that was identical to the first line in either absolute length ( absolute task ) or proportion to the height of the surrounding frame ( relative task ). The results supported the hypothesis: Whereas Japanese were more accurate in the relative task, Americans were more accurate in the absolute task. Moreover, when engaging in another culture, individuals tended to show the cognitive characteristic common in the host culture.     

Development of orientation discrimination in infancy

It has previously been found by us, with a visual evoked potential (VEP) measure, that orientation discrimination of dynamic patterns in infants can be demonstrated from around 6 weeks after birth. Experiments are reported in which orientation discrimination was measured behaviourally, in two infant control habituation procedures, with both dynamic and static patterns. When dynamic patterns identical to those in our previous VEP studies were used, the first positive evidence of orientation discrimination was found at around 6 weeks postnatally. The time course of both the VEP and the behavioural measures was similar. However, with static patterns, evidence of orientation discrimination by newborns was found if the infants were allowed to compare the habituated and novel orientations in a paired simultaneous comparison after habituation, but was not found when the habituated and novel stimulus were presented sequentially. The positive evidence of orientation discrimination in newborns supports the hypothesis that some form of orientationally tuned detectors can be used for discrimination of static patterns at birth. However, some developmental change over several weeks seems to be required before a positive electrophysiological VEP response can be measured for dynamic patterns changing in orientation.     

Young infants'' sensitivity to movement information specifying social causality

Adults and 3- to 6-month-old infants were tested for their visual preference for two different dynamic displays presented simultaneously on two side-by-side computer monitors. Each display consisted of a pair of colored discs moving either independently (the independent display) or in systematic interaction (the “chase” display), never actually contacting one another. Except for the relative spatio-temporal dependence of the discs' movements, all dynamic parameters on the two displays were controlled and maintained equal. Analysis of looking behavior showed that adults as well as infants looked differentially at the displays. Patterns of preference depended on age. For the infants who completed the experiment, there was a significant transition from more looking at the chase to more looking at the independent display as a function of age. Adults as well as the older, attentive infants, showed enhanced visual attention to the independent display. These results provide first evidence of young infants' sensitivity to movement information specifying social causality for adult observers.     

Recognition of color-form compounds by 4-month-old infants

In two studies, a paired-comparison procedure was used to investigate whether 4-month-old infants can perceive and remember correlations of color and form. In Study 1, infants were shown simultaneous presentations of two different colored shapes until two criteria for familiarization had been met. They were then offered a simultaneous choice between a colored form that they had already seen and one that was a new combination of a familiar color and a familiar shape. The infants looked significantly longer at the new combination than at the familiar combination on the test trial. In Study 2, the same procedure was used, except that the familiarization criteria were less stringent and additional analyses of the infants' test trial behavior were conducted. Infants again exhibited a significant preference for the new combination, both when looking time accumulated during the entire test-trial was analyzed and when looking just up to the “first look away” was considered. These findings that 4-months-olds can perceive and remember compounds of visual attributes conflict with the results of several studies in which the habituation and test stimuli were presented sequentially rather than simultaneously. Differences in the nature of the information processing that may be evoked by the two methods are discussed.     

The nature of infant color categorization: evidence from eye movements on a target detection task

Infants respond categorically to color. However, the nature of infants' categorical responding to color is unclear. The current study investigated two issues. First, is infants' categorical responding more absolute than adults' categorical responding? That is, can infants discriminate two stimuli from the same color category? Second, is color categorization in infants truly perceptual? Color categorization was tested by recording adults' and infants' eye movements on a target detection task. In Experiment 1, adults were faster at fixating a colored target when it was presented on a colored background from a different color category (between-category) than when it was presented on a colored background from the same color category (within-category), even when within- and between-category chromatic differences were equated in CIE (Committee International d'Eclairage) color space. This category effect was found for two chromatic separation sizes. In Experiment 2, 4-month-olds also responded categorically on the task. Infants were able to fixate the target when the background color was from the same category. However, as with adults, infants were faster at fixating the target when the target background chromatic difference was between-category than when it was within-category. This implies that infant color categorization, like adult color categorization, is truly perceptual.     

The development of depth perception from motion parallax in infancy

North Dakota State University, Fargo, North Dakota Little is known about infants' perception of depth from motion parallax, even though it is known that infants are sensitive both to motion and to depth-from-motion cues at an early age. The present experiment assesses whether infants are sensitive to the unambiguous depth specified by motion parallax and, if so, when this sensitivity first develops. Eleven infants were followed longitudinally from 8 to 29 weeks. Infants monocularly viewed a translating Rogers and Graham (1979) random-dot stimulus, which appears as a corrugated surface to adult observers. Using the infant-control habituation paradigm, looking time was recorded for each 10-sec trial until habituation, followed by two test trials: one using a depth-reversed and one using a flat stimulus. Dishabituation results indicate that infants may be sensitive to unambiguous depth from motion parallax by 16 weeks of age. Implications for the developmental sequence of depth from motion, stereopsis, and eye movements are discussed.     

Object individuation: infants' use of shape, size, pattern, and color.

Recent research indicates that when an event-monitoring paradigm is used, infants as young as 4.5 months of age demonstrate the ability to use featural information to individuate objects involved in occlusion events (Wilcox & Baillargeon, 1998a, Object individuation in infancy: The use of featural information in reasoning about occlusion events. Cognitive Psychology 37, 97-155; Wilcox & Baillargeon, 1998b, Object individuation in young infants: Further evidence with an event monitoring task. Developmental Science 1, 127-142). For example, in one experiment (Wilcox & Baillargeon, 1998b, Object individuation in young infants: Further evidence with an event monitoring task. Developmental Science 1, 127-142) 4.5-month-old infants saw a test event in which a green ball with colored dots disappeared behind one edge of a narrow or wide screen, and a red box with silver thumbtacks appeared at the other edge; the narrow screen was too narrow to hide both objects simultaneously, whereas the wide screen was sufficiently wide to hide both objects at the same time. The infants looked reliably longer at the narrow- than at the wide-screen test event. These and control results suggested that the infants had: (a) used the featural differences between the ball and box to conclude that two objects were involved in the event; (b) judged that both objects could fit simultaneously behind the wide but not the narrow screen; and hence (c) were surprised by the narrow-screen event. The present experiments build on these initial findings by investigating the features to which infants are most sensitive. Four experiments were conducted with infants 4.5-11.5 months of age using the same procedure, except that only one feature was manipulated at a time: shape, size, pattern, or color. The results indicated that 4.5-month-olds use both shape and size features to individuate objects involved in occlusion events. However, it is not until 7.5 months that infants use pattern, and 11.5 months that infants use color, to reason about object identity. It is suggested that these results reflect biases in the kind of information that infants attend to when reasoning about occlusion events. Possible sources of bias are discussed.     

A demonstration of direct access to colored stimuli following cueing by color

To test whether cueing by color can affect orienting without first computing the location of the cued color, the impact of reorienting on the validity effect was examined. In Experiment 1 subjects were asked to detect a black dot target presented at random on either of two colored forms. The forms started being presented 750 ms before the onset of a central cue (either an arrow or a colored square). In some proportion of the trials the colors switched locations 150 ms after cue onset, simultaneously with target onset. The color switch was not found to retard responses following a color cue more than following a location cue. Furthermore, it did not reduce the validity effect of the color cue: Though the validity effect of the location cue was quite larger than the validity effect of the color cue, both effects were additive with the presence/absence of a color switch. In Experiment 2, subjects were rather asked to detect a change in shape of one of the colored forms. In this case, color switch was found to affect performance even less following a color cue. The fact that across experiments, color switch did not retard neither responding nor orienting selectively in the color cue condition, indicates that when attention is set to a certain color, reorienting to a new object following color switch does not require re-computing the address of the cued color. That finding is argued to embarrass a strong space-based view of visual attention.     

Adult age differences in memory in relation to availability and accessibility of knowledge-based schemas

Three experiments investigated whether, over adulthood, the use of schemas to process and remember new information increases (developmental shift hypothesis), decreases (production deficiency hypothesis) or remains constant (age-invariance hypothesis). Effects of schema access were studied by having young, middle-aged, and old music experts and nonexperts recall information that was relevant or irrelevant to music (Experiment 1) and by comparing young and old participants' memory for prose passages when they knew or did not know the subject of the passage (Experiments 2 and 3). In each case, schema access facilitated memory equally across age levels, supporting the age-invariance hypothesis and implying that the basic structures and operations of memory do not necessarily change with age. Possible limits on the independence of age and schema utilization were considered in relation to the conditions under which each of the two alternative hypotheses might hold.     

Perceptual selectivity and information processing by fast and slow learners in paired-associate learning

Utilizing a design requiring perceptual rather than verbal discrimination in a compound-stimulus, P-A learning task, two hypotheses related to individual differences in perceptual selection of a functional stimulus cue and the processing of information were explored. The hypothesis that fast learners (determined by pretest) would “process” more information than slow learners in P-A learning was supported. Slow learners consistently ignored the random shape to which instructions specifically directed them and selected instead the context color as the functional cue. A second hypothesis that negative transfer due to proactive inhibition would be greater for slow learners was also supported.     

A developmental study of semantic elaboration and interpretation in recognition memory

Two experiments examined semantic elaboration and interpretation in recognition memory of 4-year-olds and college students. Subjects were presented pictures of color-specific and non-color-specific items, and then tested for their recognition of the chroma of the items. In Experiment 1, one-half of the presentation items were black and white and one-half colored, and testing always involved one black and white and one colored choice. In Experiment 2, all of the presentation items were colored, and testing always involved two colored choices. In both studies, the pattern of results of the two age groups was similar. Experiments 1 and 2 indicated that recognition judgments were based on representations that were elaborated with preexperimentally acquired semantic color information, and Experiment 2 also indicated that recognition judgments were based on representations that contained interpretive information about the appropriateness of the colors of the items. The results were considered to support and extend the view that when young children and adults share a common knowledge base, they are likely to engage in similar and extensive semantic processing.