Infant number perception is a topic that has been studied for many years, but many questions remain regarding what cues infants use to make these discriminations, when and how these abilities develop, and what systems are responsible for infants’ number processing. In the domain of small number perception (quantities less than four), researchers have studied the effects of continuous extent on infants’ number discrimination (Clearfield & Mix, 1999; 2001). While evidence exists that infants can use continuous extent to make discriminations, it is not clear how much influence continuous extent has on infants’ behavior in these tasks. Another issue that has not been thoroughly addressed is the role of featural information in number discrimination. Few studies exist in which featural information is manipulated so that this issue can be addressed. The current study was designed to address these issues as well as to study infant number discrimination from a developmental perspective across several ages. Infants, aged 9-, 11-, and 13-months, completed a categorization task in which they were habituated to pictures of objects (e.g. bowl, tree, shoe) in either groups of two or groups of three. They saw four different sets of objects throughout habituation. In the test phase, infants saw both new and old objects in both groups of two and three. The 9-month-olds discriminated number independent of whether the object was familiar or novel. In contrast, the 11- month-olds appeared to discriminate between the familiar and novel objects. And, the 13-month-olds exhibited a combination of these two patterns; they discriminated between the familiar and novel object when the number of objects was familiar, but not when the number of objects was novel. These data suggest that number is an easily abstracted construct and that early number representations do not contain any featural information. As infants get older, they begin to incorporate featural information into their representations, but they do so in a step-wise fashion, as demonstrated by the 13-month-olds. Therefore, featural information does not appear to be important for small number discrimination at early ages, but infants do begin to integrate featural information as they develop. / text

The present study was designed to investigate the development of infants' recognition of their fathers, specifically examining the role of multisensory information (visual and auditory cues). All infants were 4-months-old and were tested in a visual-fixation preference procedure. The two measures of interest were attention and affective responsiveness. Preference was measured by the amount of time the infants watched a visual stimulus. In Experiments 1 and 2 this stimulus was the paternal face. In Experiment 2 the paternal face was also accompanied by the paternal voice. In Experiment 3, the stimulus was the maternal face plus voice. Affective responsiveness was coded for hedonic tone, interest and excitement. It was found that infants showed more positive affect towards their fathers' faces (Experiment 1) and faces plus voices (Experiment 2), p < .05. In Experiment 3, results showed that infants preferred their mothers' faces plus voices over an unfamiliar female face plus voice when the first trial was excluded from the analysis, p < .05. These findings not only support the literature on infants' recognition of their mothers, but they also contribute to the increasing body of information on infants and their fathers. The findings are interpreted as supporting the hypothesis that the developmental pattern of father recognition is qualitatively and quantitatively different from that of mother recognition. / Ph. D.

The present research addressed the development of specialization in face processing in infancy by examining the roles of race and emotion. An other-race face among own-race faces draws adults’ attention to a greater degree than an own-race face among other-race faces due to the “other-race” feature in other-race faces. This feature underlies race-based differences in adults’ face processing. The current studies investigated the development of this mechanism as well as the influence that this mechanism has on emotion processing in infancy. In Experiment 1, Caucasian 3.5- and 9- month-olds exhibited a preference for a pattern containing an Asian face among seven Caucasian faces over a pattern containing a Caucasian face among seven Asian faces. This preference was not driven by the majority of elements in the images, because a control group of infants failed to exhibit a preference between homogeneous patterns containing eight Caucasian versus eight Asian faces. The asymmetrical attentional engagement by other-race faces indicates that the other-race feature is developed by 3.5 months of age. Like race, emotions elicit asymmetrical attention in adults: an emotional face among neutral faces is more rapidly detected than vice versa. In Experiment 2a, 9-month-olds’ preference for a pattern containing a fearful face among neutral faces over a pattern containing a neutral face among fearful faces was greater than their preference for all neutral over all fearful faces. Thus, 9-month-olds exhibited an asymmetry in the processing of emotions. Moreover, this asymmetry was not affected by the race of the faces depicting the emotion. In Experiment 2B, 3.5-month-olds failed to exhibit a preference when tested with the same procedure. Overall, the data suggest that other-race information is processed as a feature by 3.5- and 9-month-olds, which indicates that infants process other-race information in a different, perhaps categorical, manner than own-race information. Also, other-race information does not disrupt emotion processing by 9-month-olds, which suggests that emotion and race information are processed separately in infancy. Finally, the current results indicate that adult-like asymmetrical attention to emotion develops between 3.5 and 9 months of age.

The current study assessed the importance of infant detection of contingency and head and eye gaze direction in the emergence of social referencing. Five- to six-month-old infants’ detection of affect-object relations and subsequent manual preferences for objects paired with positive expressions were assessed. In particular, the role of contingency between toys’ movements and an actress’s emotional expressions as well as the role of gaze direction toward the toys’ location were examined. Infants were habituated to alternating films of two toys each paired with an actress’s affective expression (happy and fearful) under contingent or noncontingent and gaze congruent or gaze incongruent conditions. Results indicated that gaze congruence and contingency between toys’ movements and a person’s affective expressions were important for infant perception of affect-object relations. Furthermore, infant perception of the relation between affective expressions and toys translated to their manual preferences for the 3-dimensional toys. Infants who received contingent affective responses to the movements of the toys spent more time touching the toy that was previously paired with the positive expression. These findings demonstrate the role of contingency and gaze direction in the emergence of social referencing in the first half year of life.

It has been shown that infants build representations of their visual world by forming relations among its parts. However little is known about how they select the parts to relate. One possibility is that while constructing their visual world part by part they are also decomposing it, using finer and finer parts. One way to test this theory is to simply control the parts infants see. This easiest way to do this is to filter real life objects of their high and low spatial frequencies. High spatial frequencies provide information about the smaller parts where as low spatial frequencies provide information about the larger ones. By removing high or low spatial frequency we can control the coarseness of their representation and ultimately determine the level at which they function best. The present study examined infants’ ability to use high and low spatial frequencies to discriminate between objects. Infants were habituated and tested using a combination of high and low spatial frequency images. Only infants experiencing a consistent spatial frequency across habituation and test were able to discriminate between objects. Infants were also better at discriminating between objects containing high spatial frequencies. In a second study designed to be more true to life, infants were habituated to broadband images and tested using high or low spatial frequencies. This time infants did not discriminate between objects but they did look longer at low spatial frequency information than at the high. From these findings we can conclude that infants use both high and low spatial frequency information when discriminating objects, and that in certain cases one frequency may become more important than the other. The spatial frequency they use may be dependent on the context of the task. Numerous studies have shown that adults prioritize high and low spatial frequency information depending on how fast they want to process the object, the amount of detail they require, and whether they used high or low spatial frequency information during previous experiences. Infants may be similar. At times they may emphasize low spatial frequency information and the big picture. At other times they may emphasize high spatial frequency information and the detail. More studies examining how infants select information for processing are necessary and spatial frequency will likely to be an important tool in the investigation. / text

Young children’s attention to a variety of object features has been studied. However, very few studies have examined young children’s understanding of object weight. In order to investigate developmental changes in perception and categorization of weight, three tasks were given to 59 18-month-old to 3-year-old children. Three age groups (20; 27 and 34 months old) were analyzed for the final results. The first two tasks used a familiarization and novelty preference paradigm in which attention was assessed by measuring each child’s looking time. The first task’s goal was to evaluate young children’s ability to discriminate objects on the basis of weight. Children were familiarized with an object of one weight and then tested with an identical looking object that had a novel weight. Half of the subjects were familiarized to a heavy weight and half to a light weight object. Results showed a decrease in looking time over the familiarization trials (p = .0001) and an increase in attention to the novel weight (p = .0001). Thus, all children in the first task were able to discriminate object weight. Additional analyses for the first task assessed physical discrimination of object weight by examining the amount of arm movement each child exhibited within 250 milliseconds after taking an object. A significant difference in arm movement was found between the last familiarization and novel weight trials of the heavy (p = .0097) and light (p = .0001) conditions. The second task’s goal was to evaluate children’s ability to attend to object weight when appearance varies. Children were familiarized to four objects that had the same weight but differed in appearance. Half of the subjects were familiarized to heavy objects and half to light objects. After familiarization, the children were tested with one object that had the same weight but a different appearance and another object that had the same appearance but a different weight. Results revealed that the children’s looking time decreased over the familiarization trials (p = .0001). Analyses of test trials revealed that only the two older age groups had significant novelty preference scores for both the new weight and new appearance trials. The third task used a balance scale to measure understanding of weight by observing a child’s ability to pick a heavy object to make a balance scale tip. Children were given a light and heavy object with the same appearance and asked to choose which one would tip the balance scale. Results showed that only 34 month olds had significantly more correct trials (p < 0.05). In conclusion, the study’s results indicated that all young children are capable of discriminating object weight when familiarized to one object but that only the two older age groups were significantly capable of doing this when familiarized to more than one object. Results also indicated that only 34 month olds were capable of using weight differences in a more functional way, namely to tip a balance scale.

The present study was designed to investigate whether infants prefer their fathers’ voices over an unfamiliar male voice within the context of normal father-infant interaction, i.e., infant-directed (ID) speech. Twenty Caucasian male and female four-month-olds were tested in a visual-fixation preference procedure. Attentional preference was measured by the amount of time the infants watched a visual stimulus. It was found that infants did not show greater attentional or affective responsiveness to paternal ID over unfamiliar male ID speech samples. However, mothers and fathers appear to be very similar in their perception of father-infant interaction. According to these results, four-month-olds do not prefer their fathers’ voices to that of an unfamiliar male. This finding contrast sharply with the literature on maternal voice preference. The data was interpreted as supporting the hypothesis that multimodal stimulus cues are necessary for paternal voice recognition in infancy. / Master of Science