ABSTRACT Introduction: Human newborn and animal studies provide support for the intersensory redundancy hypothesis, which posits that learning is more effective when information is presented simultaneously in two modalities than one alone. Whether the same is true in the human fetus is unknown and was examined in this study. Methods: 63 low-risk fetuses (≥36 weeks gestation) were randomly assigned to one of 6 experimental groups: each group included one of 3 stimulus conditions [unimodal (music), unimodal (maternal sway) or bimodal (music and maternal sway)], and one of 2 pieces of music (music A, 4/4 time; music B, 3/4 time) composed for the study. Laboratory pre-testing included a 2 min no-music, 2 min music (A or B), 2 min no-music observation while fetal heart rate (FHR) and body movements were recorded. Subsequently, mothers carried out the assigned intervention at home, twice a day for 5 days. On day 6, laboratory testing was repeated first with the familiar (A or B) and then the novel music. Results: The initial testing showed a difference between Music A and Music B, F (1, 61) = 8.203, p <.01, where FHR decreased to Music A and increased to Music B. The same FHR response was found when fetuses were exposed to the opposite music for the first time in the novelty testing, F (1, 44) = 4.543, p <.05, following intervention. Music A elicited a response in both the unimodal music only and sway only groups, F (29, 203) = 1.871, p < .01, and F (29, 174) = 1.818, p < .01, respectively. In music B only the multimodal group showed an effect of intervention, F = (29, 203) = 1.914, p < .005. Conclusions: Fetal response to music A and B was qualitatively different. During pretesting, FHR decreased to music A and increased to music B. When the stimulus elicited an attention response (FHR decrease) learning was observed in both the unimodal or multimodal conditions. This is seen with music A (4/4 time) music where the fetus learns the stimulus. When the stimulus did not elicit a FHR decrease (Music B, 3/4 time), there was evidence that a multimodal stimulus was more effective providing some support for the intersensory redundancy hypothesis. / Thesis (Master, Nursing) -- Queen's University, 2007-10-18 16:52:55.68

Recent findings indicate that bimodal-redundant stimulation promotes perceptual learning and recruits attention to amodal properties in non-human as well as human infants. However it is not clear if bimodal-redundant stimulation can also facilitate memory during the postnatal period. Moreover, most animal and human studies have employed an operant paradigm to study memory, but have not compared the effectiveness of contingent versus passive presentation of information on memory. The current study investigated the role of unimodal versus bimodal presentation and, the role of a contingent versus passive exposure in memory retention in the bobwhite quail (Colinus virginianus). Results revealed that contingently trained chicks demonstrated a preference for the familiarized call under both unimodal and bimodal conditions. Between-group analyses revealed that the contingent-bimodal group preferred the familiarized call as compared to the passive-bimodal group. These results indicate that the contingency paradigm accompanied with the bimodal stimulus type facilitated memory during early development.

Predictions of the Intersensory Redundancy Hypothesis (IRH) state that early in development information presented to a single sense modality (unimodal) selectively recruits attention to and enhances perceptual learning of modality-specific properties of stimulation at the expense of amodal properties, while information presented redundantly across two or more modalities (bimodal) results in enhanced perceptual learning of amodal properties. The present study explored these predictions during prenatal development by assessing bobwhite quail embryos’ detection of pitch, a modality-specific property, under conditions of unimodal and redundant bimodal stimulation. Chicks’ postnatal auditory preferences between the familiarized call and the same call with altered pitch were assessed following hatching. Unimodally-exposed chicks significantly preferred the familiarized call over the pitch-modified call, whereas bimodally-exposed chicks did not prefer the familiar call over the pitch-modified call. Results confirm IRH predictions, demonstrating unimodal exposure facilitates learning of modality-specific properties, whereas redundant bimodal stimulation interferes with learning of modality-specific properties.

The Intersensory Redundancy Hypothesis (IRH; Bahrick & Lickliter, 2000, 2002, 2012) predicts that early in development information presented to a single sense modality will selectively recruit attention to modality-specific properties of stimulation and facilitate learning of those properties at the expense of amodal properties (unimodal facilitation). Vaillant (2010) demonstrated that bobwhite quail chicks prenatally exposed to a maternal call alone (unimodal stimulation) are able to detect a pitch change, a modality-specific property, in subsequent postnatal testing between the familiarized call and the same call with altered pitch. In contrast, chicks prenatally exposed to a maternal call paired with a temporally synchronous light (redundant audiovisual stimulation) were unable to detect a pitch change. According to the IRH (Bahrick & Lickliter, 2012), as development proceeds and the individual’s perceptual abilities increase, the individual should detect modality-specific properties in both nonredundant, unimodal and redundant, bimodal conditions. However, when the perceiver is presented with a difficult task, relative to their level of expertise, unimodal facilitation should become evident. The first experiment of the present study exposed bobwhite quail chicks 24 hr after hatching to unimodal auditory, nonredundant audiovisual, or redundant audiovisual presentations of a maternal call for 10min/hr for 24 hours. All chicks were subsequently tested 24 hr after the completion of the stimulation (72 hr following hatching) between the familiarized maternal call and the same call with altered pitch. Chicks from all experimental groups (unimodal, nonredundant audiovisual, and redundant audiovisual exposure) significantly preferred the familiarized call over the pitch-modified call. The second experiment exposed chicks to the same exposure conditions, but created a more difficult task by narrowing the pitch range between the two maternal calls with which they were tested. Chicks in the unimodal and nonredundant audiovisual conditions demonstrated detection of the pitch change, whereas the redundant audiovisual exposure group did not show detection of the pitch change, providing evidence of unimodal facilitation. These results are consistent with predictions of the IRH and provide further support for the effects of unimodal facilitation and the role of task difficulty across early development.

Research has shown that by 7-months of age infants demonstrate recognition of emotion by successfully matching faces and voices based on affect in an intermodal matching procedure. It is often assumed that once an ability is present the development of that ability has "ceased." Therefore, no research has examined if and how the ability to match faces and voices based on affect develops after the first 7-months. This study examined how the ability to match faces and voices based on affect changes from 7- to 12-months. Looking at infant's proportion of total looking time (PTLT) results showed that, consistent with previous research, 7-month-old infants looked significantly longer at the affectively congruent facial expression. However, 12-month- olds showed no matching of faces and voices. Further analyses showed that 7-month-olds also increased their looking to facial expressions while being presented with the affectively congruent vocal expression. Once again, 12-month-olds failed to show significant matching. That 7-month- olds were able to demonstrate matching while 12-month-olds failed to do so is possibly a result of 12-month-olds attending to other information. More research is needed to better understand how infants' recognition of affect and overall perceptual abilities change as they develop.

The development of species-typical perceptual preferences has been shown to depend on a variety of socially and ecologically derived sensory stimulation during both the pre- and postnatal periods. The prominent mechanism behind the development of these seemingly innate tendencies in young organisms has been hypothesized to be a domain-general pan-sensory selectivity process referred to as perceptual narrowing, whereby regularly experienced sensory stimuli are honed in upon, while simultaneously losing the ability to effectively discriminate between atypical or unfamiliar sensory stimulation. Previous work with precocial birds has been successful in preventing the development of species-typical perceptual preferences by denying the organism typical levels of social and/or self-produced stimulation. The current series of experiments explored the mechanism of perceptual narrowing to assess the malleability of a species-typical auditory preference in avian embryos. By providing a variety of different unimodal and bimodal presentations of a mixed-species vocalizations at the onset of prenatal auditory function, the following project aimed to 1) keep the perceptual window from narrowing, thereby interfering with the development of a species-typical auditory preference, 2) investigate how long differential prenatal stimulation can keep the perceptual window open postnatally, 3) explore how prenatal auditory enrichment effected preferences for novelty, and 4) assess whether prenatal auditory perceptual narrowing is affected by modality specific or amodal stimulus properties during early development. Results indicated that prenatal auditory enrichment significantly interferes with the emergence of a species-typical auditory preference and increases openness to novelty, at least temporarily. After accruing postnatal experience in an environment rich with species-typical auditory and multisensory cues, the effect of prenatal auditory enrichment rapidly was found to rapidly fade. Prenatal auditory enrichment with extraneous non-synchronous light exposure was shown to both keep the perceptual narrowing window open and impede learning in the postnatal environment, following hatching. Results are discussed in light of the role experience plays in perceptual narrowing during the perinatal period.