Infant directed speech (IDS) is a speech register characterized by simpler sentences, a slower rate, and more variable prosody. Recent work has implicated it in more subtle aspects of language development. Kuhl et al. (1997) demonstrated that segmental cues for vowels are affected by IDS in a way that may enhance development: the average locations of the extreme “point” vowels (/a/, /i/ and /u/) are further apart in acoustic space. If infants learn speech categories, in part, from the statistical distributions of such cues, these changes may specifically enhance speech category learning. We revisited this by asking (1) if these findings extend to a new cue (Voice Onset Time, a cue for voicing); (2) whether they extend to the interior vowels which are much harder to learn and/or discriminate; and (3) whether these changes may be an unintended phonetic consequence of factors like speaking rate or prosodic changes associated with IDS. Eighteen caregivers were recorded reading a picture book including minimal pairs for voicing (e.g., beach/peach) and a variety of vowels to either an adult or their infant. Acoustic measurements suggested that VOT was different in IDS, but not in a way that necessarily supports better development, and that these changes are almost entirely due to slower rate of speech of IDS. Measurements of the vowel suggested that in addition to changes in the mean, there was also an increase in variance, and statistical modeling suggests that this may counteract the benefit of any expansion of the vowel space. As a whole this suggests that changes in segmental cues associated with IDS may be an unintended by-product of the slower rate of speech and different prosodic structure, and do not necessarily derive from a motivation to enhance development.

We examined the effect of 4‐month‐old infants' previous experience with dogs, cats, or both and their online looking behavior on their learning of the adult‐defined category of cat in a visual familiarization task. Four‐month‐old infants' (N = 123) learning in the laboratory was jointly determined by whether or not they had experience with pets at home and how much they shifted their gaze back and forth between the stimuli during familiarization. Specifically, only infants with pets at home who also exhibited high levels of switching during familiarization remembered the individual cat exemplars or formed a summary representation of those cats. These results are consistent with recent theorizing about the processes of how infants' categorical representations are formed, and provide new understanding into how infants' categorization unfolds over time.

We investigated how exposure to pairs of different items (as compared to pairs of identical items) influences 10-month-old infants' (N = 79) categorization of horses versus dogs in an object-examining task. Infants responded to an exclusive category when familiarized with pairs of different items, but not when familiarized with pairs of identical items (Experiment 1), even when the frequency of exposure to each item was controlled (Experiment 2). When familiarized with pairs of identical items, infants failed to show evidence of memory for the individual exemplars (Experiment 3). Reducing the retention interval between presentations of different items in the identical pairs condition facilitated infants' recognition of an exclusive categorical distinction (Experiment 4). These results are discussed in terms of how exposure to collections of different items, and how opportunities to compare items, influences infants' categorization.Every day people categorize as an efficient and effective way of organizing newly acquired information. Because infants are constantly exposed to new information, the ability to form categories may be especially important for them. Indeed, a large number of studies over the last 25 years has shown impressive categorization abilities in infancy

We examined how infants’ categorization is jointly influenced by previous experience and how much they shift their gaze back-and-forth between stimuli. Extending previous findings reported by Kovack-Lesh, Horst, and Oakes (2008), we found that 4-month-old infants’ (N = 122) learning of the exclusive category of cats was related to whether they had cats at home and how much they shifted attention between two available stimuli during familiarization. Individual differences in attention assessed in an unrelated task were not related to their categorization. Thus, infants’ learning is multiply influenced by past experience and on-line attentional style.

We assessed the eye-movements of 4-month-old infants (N = 38) as they visually inspected pairs of images of cats or dogs. In general, infants who had previous experience with pets exhibited more sophisticated inspection than did infants without pet experience, both directing more visual attention to the informative head regions of the animals, particularly when comparing stimuli, and maintaining their attention to an individual animal, resisting the pull on their attention by the other visible animal. Individual differences in general attentional strategies as assessed during a pretest had similar but weaker relations to visual scanning patterns. There was some evidence that the 2 factors were interactively associated with visual inspection, supporting the findings of Kovack-Lesh and colleagues (Kovack-Lesh, Horst, & Oakes, 2008; Kovack-Lesh, Oakes, & McMurray, 2012) that infants' learning about and memory for this type of stimuli is jointly determined by pet experience and attentional style.

We examined how experience at home with pets is related to infants' processing of animal stimuli in a standard laboratory procedure. We presented 6-month-old infants with photographs of cats or dogs and found that infants with pets at home (N = 40) responded differently to the pictures than infants without pets (N = 40). These results suggest that infants' experience in one context (at home) contributes to their processing of similar stimuli in a different context (the lab), and have implications for how infants' early experience shapes basic cognitive processing.

Despite a large literature on infants' memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-old infants (N = 60) examined the effects of providing opportunities for comparison of items on infants' memory for those items. Experiment 1 revealed that 4-month-old infants failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants' memory for the distinctive features of individual items was enhanced when they could compare items.Infants can form memories for visual scenes and, with development, encode them faster and retain information for longer (see Fagan, 1990, for a review). Following 10-to 60-s of exposure to an item, 6-month-old infants consistently look longer at a novel stimulus than at the nowfamiliar stimulus (i.e., exhibiting a novelty preference) (Fagan, 1990). Younger infants, however, are less consistent, exhibiting novelty preferences (e.g., Pascalis, de Haan, Nelson, & de Schonen, 1998;Slater, Morison, & Rose, 1982), familiarity preferences (e.g., Richards, 1997;Rose, Gottfried, Mello-Carmina, & Bridger, 1982), or no clear preference (e.g., Wetherford & Cohen, 1973). Whether or not young infants exhibit a novelty preference depends on factors such as the amount of familiarization (Courage & Howe, 2001;Rose et al., 1982) and the particular stimuli (Fagan, 1974). Further, over repeated testing, infants exhibit familiarity preferences early in learning, and exhibit null or novelty preferences with more study time (e.g., Roder, Bushnell, & Sasseville, 2000). Indeed, Fagan (1990) concluded that the question "Can young infants demonstrate recognition memory?" can only be answered with "What are they being asked to recognize?" Because much or our knowledge about infants' visual memory comes from this task, it is critical to understand the processes that underlie novelty preferences. Rose and her colleagues (Rose, Feldman, & Jankowski, 2004) have shown not only developmental differences in infants' memory in this task (e.g., how much encoding time is necessary for infants to remember an item), but also similarities between infants' and adults' memory. Two seminal studies identified one potentially important factor that contributes to young infants' novelty preference (Fagan, 1978;Rose et al., 1982). Although each involved several manipulations, both studies reported the counter-intuitive finding that infants familiarized with two different items showed stronger memory than did infants familiarized with only one item. This finding is counter-intuitive (Gentner & Gunn, 2001). In addition, older children and adults have better memory for distinctive items (e.g., Arndt & Reder, 2003;Healy, Shea, Kole, & Cunningham, 2008). Thus, the same processes seem to operate at very different points in development.Befor...

We examined the interactions between visual recognition memory, working memory, and categorization by examining 6-month-old infants’ (N = 168) memory for individual items in a categorized list (e.g., images of dogs or cats). In Experiments 1 and 2, infants were familiarized with 6 different cats or dogs, presented one at a time on a series of 15-s familiarization trials. When the test occurred immediately after the sixth familiarization trial (Experiment 1), infants showed strong novelty preference for items presented on the fourth or fifth familiarization trial, but not for the items presented on the first three trials or on the sixth trial. When a brief (15-s) retention delay occurred between the end of the sixth trial and the test trials (Experiment 2), memory for the sixth item was enhanced, memory for the fourth item was impaired, and memory for the fifth was unchanged relative to when no retention delay was included. Experiment 3 confirmed that infants can form a memory for the first item presented. These results reveal how factors such as interference and time to consolidate influence infants’ visual recognition memory as they categorize a series of items.