The Effect of Gender on One-Day-Old Infants' Behavior and Heart Rate Responses to Music Decibel Level

Article excerpt

The purpose of this study was to examine gender differences among full term infants' responses to music played at a range of decibel levels. These responses were measured by physiological data (heart rate) and behavioral data (behavior state score). All subjects (N = 36) were healthy, 24-48 hours old, and had passed a hearing screening at the time of testing. Heart rate and behavior state were recorded as male (n = 18) and female (n = 18) subjects listened to alternating 3-minute periods of silence and music for 21 minutes. The music-an excerpt of an instrumental lullaby-was presented via small speakers placed on either side of each subject's head and played at three different loudness levels: 55-60 dB, 65-70 dB, and 75-80 dB. Heart rate was measured using a pulse oximeter with a Y-sensor attached to each subject's great toe, and behavior state was measured using a scale adapted from the Neonatal Behavioral Assessment Scale (Brazelton & Nugent, 1995). A two-way analysis of variance with repeated measures computed for both order and gender found no significant difference in heart rate or behavior state during the three loudness levels. Possible reasons for this lack of difference include enjoyment of the music regardless of intensity or physical inability to discriminate between the different levels.

Over the past several years, the rate of preterm births (infants born before the 37th week of pregnancy) has increased gradually in the United States. The percentage of children born preterm in the U.S. has risen between 1991 and 2000 from 10.8% to 11.6% (March of Dimes Birth Defects Foundation, 2003). In spite of this trend, the infant mortality rate decreased more than 22% in the same 10-year span. A rise in the percentage of pregnant women receiving adequate prenatal care and improvements in patient care are correlated with this statistic.

The popularity and credibility of alternative treatment modalities such as music therapy also has increased over the past decade. A recent review of music therapy medical techniques (Standley, 200Ob) cites the use of music listening with infants as a means of improving general health, decreasing the length of hospitalization, increasing tolerance for stimulation and reinforcing or structuring the achievement of developmental goals. Specifically, three basic music therapy procedures have been documented as beneficial: playing recorded, carefully selected lullabies; singing lullabies to sustain homeostasis during multimodal stimulation; and using music as reinforcement for nonnutritive sucking (Standley, 2002).

Support for the use of music with infants is not limited to music therapy literature; in fact, authors in several other fields of study have written about the benefits of using music to create a nurturing environment for infants. Such articles have been published in journals intended for nurses (Hicks, 1995; Olson, 1998; Standley, 2002), physicians (Jones & Kassity, 2001; Marwick, 2000), pédiatrie nurse practitioners (Klein & Winkelstein, 1996), and music educators (Fox, 2000). In this growing field of interest, current research has provided health care professionals with many reasons to use music in their repertoire of treatment options for newborns.

Review of Literature

Auditory sensitivity of infants. While newborn human infants are immature beings in many ways, their sense of hearing is actually quite well developed at birth; they are able to detect changes in loudness of only 3 dB and to perceive timbre and pitch much like adults do (Fassbender, 1996). With regard to the structural properties governing neonates' ability to hear, Atkinson and Braddick (1982) write the following:

The external ear is still a long way short of its adult dimensions but this is of little acoustic importance. The middle ear cavity also continues to grow during early childhood but the chain of ossicles whose properties principally determine transmission to the inner ear have reached adult dimensions and rigidity by birth. …