Seven-month-olds detect ordinal numerical relationships within temporal sequences

Previous evidence has shown that 11-month-olds represent ordinal relations between purely numerical values, whereas younger infants require a confluence of numerical and non-numerical cues. In this study, we show that when multiple featural cues (i.e., color and shape) are provided, 7-month-olds detect reversals in the ordinal direction of numerical sequences relying solely on number when non-numerical quantitative cues are controlled. These results provide evidence for the influence of featural information and multiple cue integration on infants’ proneness to detect ordinal numerical information.     

Fear,attachment and affiliation: The interaction of functional systems in 8- and 12-month-old infants

In this research fear of strangers has been analysed as it interacts with attachment and affiliation, and in relation to developmental level, in conditions most similar to the natural situations where encounters with unfamiliar persons take place. A total of 30 infants and their mothers participated. The children were divided into two groups (8-9 and 11-12 months). Each infant was approached by two females, who, in turn, produced either of two natural sequences. Our results allowed us to confirm the universality of fear and its coexistence and interaction with attachment and affiliation. As far as the role that developmental level plays, it was noted that in the 12-month-old infants fear reactions were more intense than in the younger ones. Furthermore, the attachment system was more activated in the older group in the intrusive episodes, but when the threatening nature of the situation decreased, attachment was activated less in the 12-month-old group. Another difference was related to control resources. While in the younger infants we observed a tendency to control their own emotional state, the 12-month-old infants tried to gain control over the stranger. These results were interpreted by considering the adaptative value of an increase with age of the capacity to evaluate a situation's threat value, of attachment security, and of behavioural resources permitting some control over the stranger's behaviour.     

The development of area discrimination and its implications for number representation in infancy

This paper investigates the ability of infants to attend to continuous stimulus variables and how this capacity relates to the representation of number. We examined the change in area needed by 6-month-old infants to detect a difference in the size of a single element (Elmo face). Infants successfully discriminated a 1:4, 1:3 and 1:2 change in the area of the Elmo face but failed to discriminate a 2:3 change. In addition, the novelty preference was linearly related to the ratio difference between the novel and familiar area. Results suggest that Weber's Law holds for area discriminations in infancy and also reveal that at 6 months of age infants are equally sensitive to number, time and area.     

Rapid development of feature binding in visual short-term memory

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.     

Ordinal judgments of numerical symbols by macaques (Macaca mulatta)

Two rhesus monkeys (Macaca mulatta) learned that the arabic numerals 0 through 9 represented corresponding quantities of food pellets. By manipulating a joystick, the monkeys were able to make a selection of paired numerals presented on a computer screen. Although the monkeys received a corresponding number of pellets even if the lesser of the two numerals was selected, they learned generally to choose the numeral of greatest value even when pellet delivery was made arrhythmic. In subsequent tests, they chose the numerals of greater value when presented in novel combinations or in random arrays of up to five numerals. Thus, the monkeys made ordinal judgments of numerical symbols in accordance with their absolute or relative values.     

Working memory deficits in developmental dyscalculia: The importance of serial order

Although a number of studies suggests a link between working memory (WM) storage capacity of short-term memory and calculation abilities, the nature of verbal WM deficits in children with developmental dyscalculia (DD) remains poorly understood. We explored verbal WM capacity in DD by focusing on the distinction between memory for item information (the items to be retained) and memory for order information (the order of the items within a list). We hypothesized that WM for order could be specifically related to impaired numerical abilities given that recent studies suggest close interactions between the representation of order information in WM and ordinal numerical processing. We investigated item and order WM abilities as well as basic numerical processing abilities in 16 children with DD (age: 8–11 years) and 16 typically developing children matched on age, IQ, and reading abilities. The DD group performed significantly poorer than controls in the order WM condition but not in the item WM condition. In addition, the DD group performed significantly slower than the control group on a numerical order judgment task. The present results show significantly reduced serial order WM abilities in DD coupled with less efficient numerical ordinal processing abilities, reflecting more general difficulties in explicit processing of ordinal information.     

Increasing magnitude counts more: asymmetrical processing of ordinality in 4-month-old infants

While infants' ability to discriminate quantities has been extensively studied, showing that this competence is present even in neonates, the ability to compute ordinal relations between magnitudes has received much less attention. Here we show that the ability to represent ordinal information embedded in size-based sequences is apparent at 4months of age, provided that magnitude changes involve increasing relations. Infants in Experiments 1A and 1B discriminated changes in ordinal relations after habituation to ascending sequences, but did not show evidence of discrimination after habituation to descending sequences. In Experiment 2 we replicated this asymmetry in magnitude discrimination even when additional cues known to boost ordinal competence were provided. The presence of an asymmetry between ascending vs. descending order during infancy suggests a developmental continuity in the underlying code used to represent magnitude, whereby the reported addition advantage in children and adults' arithmetic performance emerges.     

The other-race effect develops during infancy: evidence of perceptual narrowing

Experience plays a crucial role in the development of face processing. In the study reported here, we investigated how faces observed within the visual environment affect the development of the face-processing system during the 1st year of life. We assessed 3-, 6-, and 9-month-old Caucasian infants' ability to discriminate faces within their own racial group and within three other-race groups (African, Middle Eastern, and Chinese). The 3-month-old infants demonstrated recognition in all conditions, the 6-month-old infants were able to recognize Caucasian and Chinese faces only, and the 9-month-old infants' recognition was restricted to own-race faces. The pattern of preferences indicates that the other-race effect is emerging by 6 months of age and is present at 9 months of age. The findings suggest that facial input from the infant's visual environment is crucial for shaping the face-processing system early in infancy, resulting in differential recognition accuracy for faces of different races in adulthood.     

The development of ordinal numerical competence in young children

Two experiments assessed ordinal numerical knowledge in 2- and 3-year-old children and investigated the relationship between ordinal and verbal numerical knowledge. Children were trained on a 1 vs 2 comparison and then tested with novel numerosities. Stimuli consisted of two trays, each containing a different number of boxes. In Experiment 1, box size was held constant. In Experiment 2, box size was varied such that cumulative surface area was unrelated to number. Results show children as young as 2 years of age make purely numerical discriminations and represent ordinal relations between numerosities as large as 6. Children who lacked any verbal numerical knowledge could not make ordinal judgments. However, once children possessed minimal verbal numerical competence, further knowledge was entirely unrelated to ordinal competence. Number may become a salient dimension as children begin to learn to count. An analog magnitude representation of number may underlie success on the ordinal task.     

Beyond quantity: Individual differences in working memory and the ordinal understanding of numerical symbols

In two different contexts, we examined the hypothesis that individual differences in working memory (WM) capacity are related to the tendency to infer complex, ordinal relationships between numerical symbols. In Experiment 1, we assessed whether this tendency arises in a learning context that involves mapping novel symbols to quantities by training adult participants to associate dot-quantities with novel symbols, the overall relative order of which had to be inferred. Performance was best for participants who were higher in WM capacity (HWMs). HWMs also learned ordinal information about the symbols that lower WM individuals (LWMs) did not. In Experiment 2, we examined whether WM relates to performance when participants are explicitly instructed to make numerical order judgments about highly enculturated numerical symbols by having participants indicate whether sets of three Arabic numerals were in increasing order. All participants responded faster when sequential sets (3-4-5) were in order than when they were not. However, only HWMs responded faster when non-sequential, patterned sets (1-3-5) were in order, suggesting they were accessing ordinal associations that LWMs were not. Taken together, these experiments indicate that WM capacity plays a key role in extending symbolic number representations beyond their quantity referents to include symbol-symbol ordinal associations, both in a learning context and in terms of explicitly accessing ordinal relationships in highly enculturated stimuli.     

Stress changes the representational landscape: evidence from word segmentation

Over the past couple of decades, research has established that infants are sensitive to the predominant stress pattern of their native language. However, the degree to which the stress pattern shapes infants' language development has yet to be fully determined. Whether stress is merely a cue to help organize the patterns of speech or whether it is an important part of the representation of speech sound sequences has still to be explored. Building on research in the areas of infant speech perception and segmentation, we asked how several months of exposure to the target language shapes infants' speech processing biases with respect to lexical stress. We hypothesize that infants represent stressed and unstressed syllables differently, and employed analyses of child-directed speech to show how this change to the representational landscape results in better distribution-based word segmentation as well as an advantage for stress-initial syllable sequences. A series of experiments then tested 9- and 7-month-old infants on their ability to use lexical stress without any other cues present to parse sequences from an artificial language. We found that infants adopted a stress-initial syllable strategy and that they appear to encode stress information as part of their proto-lexical representations. Together, the results of these studies suggest that stress information in the ambient language not only shapes how statistics are calculated over the speech input, but that it is also encoded in the representations of parsed speech sequences.     

The developmental roots of the speed-accuracy trade-off

The speed of adult reaching movements is lawfully related to the distance of the reach and the size of the target. The authors had 7-, 9-, and 11-month-old infants reach for small and large targets to investigate a possible relation between the emergence of this speed-accuracy trade-off and the improvements in infants' ability to pick up tiny objects. By 7 months of age, infants slowed down their reaches for smaller objects. The authors concluded that it was not the ability to use a precision grip that facilitated the speed-accuracy trade-off but rather the other way around. The slowing down toward the end of the movement might set the conditions for the development of fine distal control of the hand.     

Stable individual differences in number discrimination in infancy

Previous studies have shown that as a group 6-month-old infants successfully discriminate numerical changes when the values differ by at least a 1:2 ratio but fail at a 2:3 ratio (e.g. 8 vs. 16 but not 8 vs. 12). However, no studies have yet examined individual differences in number discrimination in infancy. Using a novel numerical change detection paradigm, we present more direct evidence that infants' numerical perception is ratio-dependent even within the range of discriminable ratios and thus adheres to Weber's Law. Furthermore, we show that infants' numerical discrimination at 6 months reliably predicts their numerical discrimination abilities but not visual short-term memory at 9 months. Thus, individual differences in numerical discrimination acuity may be stable within the first year of life and provide important avenues for future longitudinal research exploring the relationship between infant numerical discrimination and later developing math achievement.     

Changes in interhemispheric transfer rate and the development of bimanual coordination during childhood

Based on recent models of the ontogeny of memory (Nelson, 1995), we hypothesize that 6-month-old infants should show evidence of repetition priming. Event-related potentials were recorded from 11 scalp sites to novel and primed upright and inverted faces. In Experiment 1 (n = 24), 6-month-old infants viewed faces that were repeated after 6 to 12 images. Overall, repeated faces demonstrated greater negativity than novel faces and upright faces demonstrated greater negativity than inverted faces. In order to ground these results in an adult model, a group of adults (n = 30) was tested in a similar experiment. Here we observed effects of repetition at an early positive component labeled the P150 as well as at the P300, with repeated images being more positive than novel images. These data support the idea that infants at 6 months are capable of revealing electrophysiological evidence of perceptual priming.     

Neural and behavioral correlates of visual recognition memory in 4- and 8-month-old infants.

The neural and behavioral correlates of the 4- and 8-month-old infant's ability to distinguish between frequently and infrequently presented familiar and novel events was examined. Cortical event-related potentials (ERPs) were recorded as infants were familiarized to two faces. During the test trials that followed, one of these faces was presented frequently, and the other infrequently; on each of the remaining 20% of the trials, a previously unseen, novel face was presented. Following the ERP phase, infants' looking times were recorded to pairs of faces, some of which had been seen during the ERP testing, and some of which had not. At 4 months the ERP activity invoked by the three classes of events was similar, suggesting that infants were unable to distinguish among them. At 8 months the ERP activity differed only between the Infrequent Novel events and the two classes of familiar events, but did not differ between the frequently and infrequently presented familiar events. The ERP findings complement previously reported data from 6-month-old infants in describing a trend whereby infants become increasingly able to respond to stimuli on the basis of whether they have been seen before, and not on the basis of how often they had been seen. The behavioral data at both 4 and 8 months were less clear cut than the ERP data. These findings are discussed in the context of the neural and cognitive processes involved in dissociating probability information from novelty detection.     

Attentional SNARC: there's something special about numbers (let us count the ways)

We report a study that examines whether the presentation of irrelevant, ordinal information at central fixation interacts with the allocation of attention beyond fixation. Previous research has demonstrated that number perception influences the allocation of spatial attention, such that the presentation of a spatially nonpredictive number at fixation results in attention being allocated to the left when the central number is low (e.g., 1), and attention being allocated to the right when the central number is high (e.g., 9). Here, we examine whether this attentional SNARC effect (spatial numerical association of response codes) generalizes to other ordinal sequences: letters, days, and months. Though we replicate the attentional SNARC we find that this effect is number-specific, unless participants are required to process the cue in an order-relevant fashion. This discovery of number-specificity has important implications both for the functional separation between SNARC and attention-SNARC effects, as well as lending support to recent theories regarding the specificity of a shared neural architecture between numbers and visuospatial attention.     

Development of ordinal sequence perception in infancy

Perception of the ordinal position of a sequence element is critical to many cognitive and motor functions. Here, the prediction that this ability is based on a domain‐general perceptual mechanism and, thus, that it emerges prior to the emergence of language was tested. Infants were habituated with sequences of moving/sounding objects and then tested for the ability to perceive the invariant ordinal position of a single element (Experiment 1) or the invariant relative ordinal position of two adjacent elements (Experiment 2). Experiment 1 tested 4‐ and 6‐month‐old infants and showed that 4‐month‐old infants focused on conflicting low‐level sequence statistics and, therefore, failed to detect the ordinal position information, but that 6‐month‐old infants ignored the statistics and detected the ordinal position information. Experiment 2 tested 6‐, 8‐, and 10‐month‐old infants and showed that only 10‐month‐old infants detected relative ordinal position information and that they could only accomplish this with the aid of concurrent statistical cues. Together, these results indicate that a domain‐general ability to detect ordinal position information emerges during infancy and that its initial emergence is preceded and facilitated by the earlier emergence of the ability to detect statistical cues.     

婴儿共同注意能力的发展

本研究采用严格的实验室测验法,从年龄趋势、学习能力、性别差异三方面考察了8～11个月婴儿共同注意能力的发展。结果表明：1）婴儿的共同注意力在8～11个月间逐步提高,9个月左右出现显著的发展性变化,但1岁以前,该能力的发展水平都较低;2）就共同注意而言,婴儿具有从练习经验中学习的可能性,且学习能力存在年龄差异,8个月的婴儿基本不能从练习中受益,而8个月以上的其他三组婴儿在练习后共同注意水平都有不同程度的提高;3）总体而言,女婴共同注意能力的发展水平显著地高于男婴。     

Number bias for the discrimination of large visual sets in infancy

This brief report attempts to resolve the claim that infants preferentially attend to continuous variables over number [e.g. Psychol. Sci. 10 (1999) 408; Cognit. Psychol.44 (2002) 33] with the finding that when continuous variables are controlled, infants as young as 6-months of age discriminate large numerical values [e.g. Psychol. Sci. 14 (2003) 396; Cognition 89 (2003) B15; Cognition 74 (2000) B1]. In two parallel experiments, we compare 6-month-old infants' ability to discriminate number and ignore continuous variables with their ability to form a representation of a cumulative surface area and ignore number. We find that infants discriminate a 2-fold change in number but fail to discriminate a 2-fold change in cumulative surface area. The results point to a more complicated relationship between discrete and continuous dimensions than implied by previous literature.     

Temporal discrimination increases in precision over development and parallels the development of numerosity discrimination

Time perception is important for many aspects of human behavior, and a large literature documents that adults represent intervals and that their ability to discriminate temporal intervals is ratio dependent. Here we replicate a recent study by vanMarle and Wynn (2006) that used the visual habituation paradigm and demonstrated that temporal discrimination in 6-month-old infants is also ratio dependent. We further demonstrate that between 6 and 10 months of age temporal discrimination increases in precision such that by 10 months of age infants succeed at discriminating a 2:3 ratio, a ratio that 6-month-old infants were unable to discriminate. We discuss the potential implications of the fact that temporal discrimination follows the same developmental progression that has been previously observed for number discrimination in infancy (Lipton & Spelke, 2003).