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The Development of the Perception of Music
The development of music perception refers to the way in which humans develop an understanding of music and it’s components. The ability to perceive music requires an understanding of many cognitive components including pitch, timbre, melody, rhythm, tempo, and harmonic. The perception of music is not a process which humans have to learn consciously but gradually develops at different rates across infancy and into adulthood.

Stages of Development
During infancy, there are many cognitive processes that contribute towards the development of music perception. These include perceptual grouping, defined as the ability to group sounds together on the basis of information about pitch and tempo. Following this the infant will develop the ability to distinguish the difference between two notes that rapidly alternate between two pitches otherwise known as the   ability to segregate a sequence. Other aspects of music perception that develop during infancy include an ability to detect changes in melodies and discriminate between two rhythmic patterns as well as developing a good understanding of pitch. In childhood, singing behaviour will develop as well as an understanding of absolute pitch. This is defined as the ability to identify notes in music even when they are played alone without any musical context or background, for example, being able to recognize the middle C note on a piano. Furthermore,children will start to be able to associate pieces of music with particular emotional states and will gain knowledge of the timing and rhythmic patterns, especially for music popular within their culture. In Adulthood, an important role in the development of music perception is music experience and memory for music. Much research has been conducted into the role of experience on music perception in comparison to non-musicians and its relation to memory. As the development of music perception is such a vast area of research, this article will focus on the very beginning of the development of music perception by looking at music perception in prenatal infants.

The Biology of the Prenatal Auditory System
It is thought that the auditory system is fully functional at 25 weeks gestation. However there is variability in these findings, and most research conducted on fetal hearing have been conducted within the third trimester of pregnancy, which begins at 28 weeks gestation. The first stage of auditory development begins at 20 weeks,when the fetus develops the structural parts of the ears. After this the neuro-sensory part of auditory development begins. The most important brain areas responsible for auditory development are the auditory cortex and the temporal lobe. Musical features such as pitch and timbre are extracted from the auditory cortex, and this information is then transferred into Auditory Sensory Memory” In order for the auditory system to develop properly it is important that the fetus receives auditory stimulation from the environment in the womb and straight after birth. Although loud frequency background noise can interfere with auditory development and subsequent frequency discrimination.

Prenatal Development of Pitch
As the ability to discriminate between sounds is necessary for successful auditory development, researchers have tested prenatal infants  ability to discriminate between sounds of different frequencies. An early study by Shelter showed that infants could recognize their mothers voice from as early as the second trimester. It has been suggested that this may be due to the infant developing an understanding of the patterns in their mothers voices. In relation to the recognition of sounds of different pitch, a fetus is more likely to respond to sounds of high frequencies. This can be seen in an increase in fetal movements when a sound with a frequency of 200hz is presented to the fetus. This is because the sound is exaggerated at the surface of the abdominal wall and through the abdominal tissues and fluids. Research has also shown the importance of the noise environment for the fetus, as when exposed to background noise greater than 60 decibels,infants cannot tell the difference between sounds.

This has been verfied in newborns, who when presented with a list of words in either Japanese or French are able to extract information about pitch. Research focused on the development of pitch perception has shown that infants develop the ability to discriminate between two Pure tone between 27 to 35 weeks of gestation. When presented with either pure tones, ranging in frequency from 250hz to 500hz or two speech sounds, the fetus was able to tell the difference between the sounds at 35 weeks but was less successful in doing this at 27 weeks.

Prenatal Development of Tone and Tempo
The perception of tone refers to the ability to detect the overall quality of a vocal sound whilst tempo refers to the speed at which a passage of music is played. Evidence of prenatal development of tempo and tone can be demonstrated through the infant showing a preference for one sound over another. When given vocal sounds,fetuses have shown preference for their mother's voice over new sounds.In one experiment,fetuses were read a rhyme in either their mother's voice or a stranger's voice everyday between 33 weeks gestation and 37 weeks gestation. The results showed that infants had increased heart rates when they heard their mother's voice, suggesting that recognition of the mother's voice develops during the third trimester. It has been shown that infants also show varied responses to different types of music. A further study showed that 33% of fetal subjects responded differently to variations in tempo,when played faster and slower selections of music. It has also been demonstrated that fast paced music caused more of an active response from prenates, whilst lullabies and calming classical music such as Vivaldi and Mozart elicit a calming effect on unborn infants.

Prenatal development of Rhythm
Less research has been done investigating prenatal infant's ability to distinguish between rhythms. Some research by Henry Truby has suggested that after six months of age the fetus can move in time to their mother's speech. In relation to music, embryologist Dr. William Liley, conducted an experiment in which he found that when listening to an orchestral performance, an unborn child could move with the Timpanists,(a person who plays the kettle drums),contribution to a song, from about 25 weeks onwards. It has also been suggested that infants will respond to the rhythms tapped onto the mother's stomach.

What is Transnatal Memory?
Transnatal memory is the process in which a fetus can retain information learnt in the womb after birth. Research in this area tends to use either musical sounds, presented to the fetus in the form of rhymes or songs, or verbal sounds such as maternal voice and storytelling.

How is Transnatal Memory Tested?
When testing transnatal memory, sounds are usually presented repeatedly to the fetus for a number of weeks. This testing usually occurs within the third trimester or after the fetuses's auditory system is thought to be fully functioning at 25 weeks. Once the infants are born, they are tested on whether they have retained the information learnt in the womb in a variety of ways. Generally it has been shown that infants do have the ability to retain knowledge of the stimuli presented to them but it is not clear how long the information is retained for or whether it is stored in short term or long term memory. Traditional methods used to test transnatal memory are varied. Learning within the womb can be measured using foetal heart rate and the frequency of kicking and movement. Outside of the womb, one procedure which is commonly used is newborn's heart rate to a sound that they had been presented with before birth. Studies have shown that an increase in heart rate demonstrates that the infant recognizes and is familiar with the sound being presented to them. A Study by Hepper repeatedly exposed prenatal infants to a popular theme tune from a TV Programme. After birth the infants heart rates were measured in response to the theme tune. The results showed that the infants exhibited changes in heart rate and an increase in the number of body movements, when the theme tune was played for up to two to four days after birth.This supports the idea that learning occurs within the womb.The infants were tested again using changes in heart rate or bodily movement at 21 days old. They showed no evidence of learning or memory for the theme song suggesting that the learning of the theme tune is only temporarily stored in the infants mind and not in long term memory. Another popular technique used to test transnatal memory is a method used in as series of experiments by Decasper and Spence. In their procedure, newborn infant's were presented with a story learnt in the womb or new novel story. In order to measure which sound infants preferred they were given two bottles to suck on. One bottle played the novel story and the other bottle played the familiar stimuli. In this procedure If the infants have learned and retained information from the womb they should suck more on the bottle that produces the stimuli played to them in the womb, whilst a control group that had no prenatal experience of either of the sounds presented to them should show no preference. Similar methodologies have also been used in other studies, including playing two sounds from different directions in which after habituation, the infant is required to look either left or right in response to a sound that is either familiar or non-familiar. The amount of time the infants spend looking either left or right in response to the presented sounds is then measured.It is expected that the infant will look longer in the direction of the sound they are familiar with.

Evidence for Transnatal Memory
There are many studies which have been carried out that provide support for the notion that infants have Transnatal memory. Evidence has shown that when newborns are given a choice of listening to a melody sung by their mother in the womb or a new melody also sung by their mother, they prefer the melody that was sung to them in the womb. In the series of Studies conducted on Transnatal Memory by Decasper and Spence, it has also demonstrated that newborn infants show recognition of their mothers voices from birth. In the study, mothers read a particular passage to their infant before birth, for the last six weeks of their pregnancy. When tested after birth, infants showed a preference for and gained more enjoyment from the passage the mother had read to them during pregnancy. Furthermore the infants showed equal preference for speech that resembled the sounds heard in the womb and normal sounds, whilst infants who had no prenatal exposure to the sounds showed preference only for the normal sounds, suggesting that infants have memory for the sounds and frequencies they hear in the womb.

The Mozart Effect
The Mozart effect is the belief that listening to classical music during pregnancy will enhance an infant's cognitive abilities. It is thought that music training and early musical exposure can promote the development of spatial reasoning. The idea stems from research conducted at the University of California in the 1990's by Francis Rauscher and Shaw. The original study was conducted on college students, rather than infants.The researchers found that that subjects who listened to Mozart's Sonata in D major showed improvement on spatial reasoning tasks, but the improvement only lasted for ten minutes. A follow up study by Rauscher and Shaw using a larger sample found similar results. Another long term study was conducted to see whether similar results could be found in preschool children, looking at the effects of early music lessons on spatial reasoning tasks.The researchers found that children who had piano lessons showed improvement in spatial reasoning supporting the idea that exposure to music during this time can improve cognitive development.

A study by LaFucnte in 1997 also found support for the Mozart effect. In this study, mothers played audiotapes,made up of simple musical sounds from either 28 or 30 weeks of pregnancy onwards. During this time the simple sounds played to the fetus were gradually made more complex. Infants were subsequently tested on their cognitive development in the first six months of life. They showed more rapid development of several behaviours including hand-eye co-ordination, eye tracking and facial imitation. Whilst replication of the Mozart Effect was found by LaFucnte, many researchers have failed to replicate the results found by Rauscher and Shaw leading to debate as to whether the effect actually exists or not. Rauscher and Shaw stated that failure to replicate the Mozart Effect in other laboratory experiments could be due to researchers not following key steps in the procedure during testing. They provided researchers with a list of these key components. However, an experiment designed to replicate the Mozart Effect using the list and instructions provided by Raushcher and Shaw still failed to find a significant Mozart Effect.The authors conclude that there is little evidence to support basing intellectual programs for children on the Mozart Effect. Another experiment comparing children's scores on a spatial intelligence test after listening to either Mozart or a piece of popular dance music, found no significant difference in scores between the two groups. It also remains unclear what the optimal amount of music exposure is for children or the earliest age at which listening to classical music can have an effect. It has been suggested that there is only little support can be found for the Mozart effect, and any findings suggesting that music does enhance spatial reasoning have been applicable to only a small amount of people. Nevertheless since the study was published there has been an increase in the number of people buying Mozart music and playing it to their infants.