Nonhuman Infants Research Articles

Positive Valence Contributes to Hyperarticulation in Maternal Speech to Infants and Puppies.

Infant-directed speech often has hyperarticulated features, such as point vowels whose formants are further apart than in adult-directed speech. This increased "vowel space" may reflect the caretaker's effort to speak more clearly to infants, thus benefiting language processing. However, hyperarticulation may also result from more positive valence (e.g., speaking with positive vocal emotion) often found in mothers' speech to infants. This study was designed to replicate others who have found hyperarticulation in maternal speech to their 6-month-olds, but also to examine their speech to a non-human infant (i.e., a puppy). We rated both kinds of maternal speech for their emotional valence and recorded mothers' speech to a human adult. We found that mothers produced more positively valenced utterances and some hyperarticulation in both their infant- and puppy-directed speech, compared to their adult-directed speech. This finding promotes looking at maternal speech from a multi-faceted perspective that includes emotional state.

Inter-human and animal-directed empathy: A test for evolutionary biases in empathetic responding

Empathy is facilitated by the perceived similarity between the object and subject. Conversely, nurturance has been suggested to influence empathy, in that humans have an ability to empathise with non-kin in a similar way as with their own offspring when certain characteristics (e.g., childlikeness) are present. To examine the combined effects of similarity and nurturance, participants (n=69) were presented with images of infant and adult human and wild non-human animals (non-human primates, quadruped wild mammals, and wild birds) depicted in negative, victimising situations. Stronger phasic skin conductance responses and subjective ratings of empathy and arousal were observed for phylogenetically similar species. Subjective empathy and arousal ratings were greater for human infants but this did not extend to the non-human infants. Heart rate was lower during infant than adult stimuli presentations, however, the magnitude of change resembled that previously reported for neutral stimuli presentations. Although a similarity effect is widely acknowledged in the literature, the present findings point to the importance of taking into account both the age and the level of similarity with the target to gain a fuller understanding of empathy towards others of our own and different species.

Inhibition of the Alternative Pathway of Nonhuman Infant Complement by Porin B2 Contributes to Virulence of Neisseria meningitidis in the Infant Rat Model

Neisseria meningitidis utilizes capsular polysaccharide, lipooligosaccharide (LOS) sialic acid, factor H binding protein (fHbp), and neisserial surface protein A (NspA) to regulate the alternative pathway (AP) of complement. Using meningococcal mutants that lacked all four of the above-mentioned molecules (quadruple mutants), we recently identified a role for PorB2 in attenuating the human AP; inhibition was mediated by human fH, a key downregulatory protein of the AP. Previous studies showed that fH downregulation of the AP via fHbp or NspA is specific for human fH. Here, we report that PorB2-expressing quadruple mutants also regulate the AP of baby rabbit and infant rat complement. Blocking a human fH binding region on PorB2 of the quadruple mutant of strain 4243 with a chimeric protein that comprised human fH domains 6 and 7 fused to murine IgG Fc enhanced AP-mediated baby rabbit C3 deposition, which provided evidence for an fH-dependent mechanism of nonhuman AP regulation by PorB2. Using isogenic mutants of strain H44/76 that differed only in their PorB molecules, we confirmed a role for PorB2 in resistance to killing by infant rat serum. The PorB2-expressing strain also caused higher levels of bacteremia in infant rats than its isogenic PorB3-expressing counterpart, thus providing a molecular basis for increased survival of PorB2 isolates in this model. These studies link PorB2 expression with infection of infant rats, which could inform the choice of meningococcal strains for use in animal models, and reveals, for the first time, that PorB2-expressing strains of N. meningitidis regulate the AP of baby rabbits and rats.

What makes a cry a cry? A review of infant distress vocalizations

Abstract In contrast to the cries of human infants, sounds made by non-human infants in different stressful behavioral contexts (hunger or physical discomfort, isolation, capture by humans or predators) are usually treated as distinct types of vocalizations. However, if distress vocalizations produced by different species and in different contexts share a common motivational state and associated neurochemical pathways, we can expect them to share a common acoustic structure and adaptive function, showing only limited variation that corresponds to the infant’s level of arousal. Based on this premise, we review the acoustic structure and adaptive function of two types of distress calls, those given when infants were isolated from their mothers (isolation calls) or captured by humans (capture calls). We conducted a within-context comparison examining the two call types across a diverse selection of mammalian species and other vertebrate groups, followed by a comparison of how acoustic structure and function differs between these contexts. In addition, we assessed acoustic traits that are critical to the response of caregivers. Across vertebrate species, distress vocalizations produced in these two behavioral contexts tend to be tonal with a simple chevron, flat or descending pattern of frequency modulation. Reports that both isolation and capture calls of vertebrate infants serve to attract care-givers are universal, and the fundamental frequency of infant vocalizations is often critical to this response. The results of our review are consistent with the hypothesis that differences in the acoustic structure of isolation and capture distress vocalizations reflect differences in arousal, and not discrete functions. The similarity in acoustic structure and caregiver response observed across vertebrates adds support to the hypothesis that the production and processing of distress vocalizations are part of a highly-conserved system of social vocal behaviour in vertebrates. Bioacoustic research may move forward by recognizing the commonality among different forms of infant solicitations that attract caregivers, and the commonality of these solicitations with vocalizations that attract conspecifics in still other behavioral contexts.

Immunogenicity of a meningococcal native outer membrane vesicle vaccine with attenuated endotoxin and over-expressed factor H binding protein in infant rhesus monkeys

We previously investigated immunogenicity of meningococcal native outer membrane vesicle (NOMV) vaccines prepared from recombinant strains with attenuated endotoxin (ΔLpxL1) and over-expressed factor H binding protein (fHbp) in a mouse model. The vaccines elicited broad serum bactericidal antibody responses. While human toll-like receptor 4 (TLR-4) is mainly stimulated by wildtype meningococcal endotoxin, mouse TLR-4 is stimulated by both the wildtype and mutant endotoxin. An adjuvant effect in mice of the mutant endotoxin would be expected to be much less in humans, and may have contributed to the broad mouse bactericidal responses. Here we show that as previously reported for humans, rhesus primate peripheral blood mononuclear cells incubated with a NOMV vaccine from ΔLpxL1 recombinant strains had lower proinflammatory cytokine responses than with a control wildtype NOMV vaccine. The cytokine responses to the mutant vaccine were similar to those elicited by a detergent-treated, wildtype outer membrane vesicle vaccine that had been safely administered to humans. Monkeys (N=4) were immunized beginning at ages 2–3 months with three doses of a NOMV vaccine prepared from ΔLpxL1 recombinant strains with over-expressed fHbp in the variant 1 and 2 groups. The mutant NOMV vaccine elicited serum bactericidal titers ≥1:4 against all 10 genetically diverse strains tested, including 9 with heterologous PorA to those in the vaccine. Negative-control animals had serum bactericidal titers <1:4. Thus, the mutant NOMV vaccine elicited broadly protective serum antibodies in a non-human infant primate model that is more relevant for predicting human antibody responses than mice.

Brief report: Can contingent imitation reinforce truck lifting in a three-month-old infant?

Infant leg lifting is a well-researched operant response and now forms the basis of many childhood activities. Contingent imitation is a process where the trainer often will imitate the activities of the subject and attempt to get an increase in those activities. Gradually in the contingent imitation procedure variation is introduced in an attempt to get the subject to reciprocate the imitation process by incorporating it into the behavioral routine. This study explores the first part of the contingent imitation exercise- can contingent imitation increase trunk lifting in a three-month-old infant. We used an ABA design to explore this phenomenon. In the first phase, the infant was placed on a bed where the number of spontaneous lifts was recorded over a 90 second period. In the next phase the experimenter lay next to the infant and imitated all the infants' motor behavior. Only the number of lifts of the legs raising the trunk was recorded, since it was the easiest behavior to clearly mark occurrence. Contingent on the infants lifting of the legs and trunk, the experimenter would lift their legs and trunk. This was recorded over a 90 second interval. In the final phase, the experimenter left the room for 90 seconds and the number of lifting was recorded. In the baseline phase the infant averaged 3 lifting in a thirty second period, during intervention lifting rate went to approximately an average of 4-lifts/ thirty-minute intervals. In the return to backline phase, the infant averaged 2lifts/ 30-second intervals. These results support the use of contingent imitation to serve as reinforcement for infants trunk lifting. Key words: contingent imitation, leg and trunk lifting, infant operant response ********** Infants are known to respond from birth to primary reinforcers. A variety of primary reinforcers exist to meet infant's basic biological needs. For example, both human and nonhuman infants are poor thermo-regulators, so closeness to parent skin from birth provides reinforcing qualities. Sensory-ecological reinforcers (Novak & Paleaz, 2005) are also apparent at very early age. For example, Harlow (1958) discovered that soft items were reinforcing over hard items for neonatal macaque monkeys. Contingent imitation (Gazdag, & Warren, 2000) is a process in which the trainer will imitate a child's behavior. After repeated episodes, the trainer will then introduce a 5% variation in the cycle in attempt to get the child to imitate the change. For contingent imitation to be effective the response being imitated has to serve as a sensory reinforcer to increase the frequency of responding. This study attempts to determine if imitation of a child's response can reinforce that response in a three-month-old infants. Thus, imitation of a child's trunk and buttocks lift would need to increase the frequency of trunk and buttocks lifting for the child. Previous research has shown that three month old infants' leg movements readily come under control of operant ecological reinforcement (Merriman, Rovee-Collier, & Wilk, 1997). METHODS Subject Subject was born at 9lbs and 15 ounces. She was 22 inches at birth. This placed her in the 99%ile for weight and the 98%ile for height. At the time of the study the subject was 3 months old, 25 inches in length and weighed 17 lbs. The subject was no stranger to leg movements for reinforcement (see Dziewolska & Cautilli, 2005; Cautilli & Dziewolska, 2005). In addition, since approximately 6 weeks old, the subject used a kick and play chair, which presents reinforcement in the form of lights and music when the child kicks. Design Since this infant had a lot of experience with kicking to produce reinforcement, it was decided for this study a more complex and physically difficult response would be chosen: trunk lift. A trunk lift was defined as when the infant was lying in the supine position a complete lifting of the legs and buttocks off of the floor. …

Question From the Clinician

Question From the Clinician