Life stages of psychological development
Pre-natal development
Pre-natal development is of interest to psychologists investigating the context of early psychological development. The whole prenatal development involves three main stages: germinal stage, embryonic stage and fetal stage. Germinal stage begins at conception until 2 weeks; embryonic stage means the development from 2 weeks to 8 weeks; fetal stage represents 9 weeks until birth of the baby.[40] The senses develop in the womb itself: a fetus can both see and hear by the second trimester (13 to 24 weeks of age). Sense of touch develops in the embryonic stage (5 to 8 weeks).[34]:97 Most of the brain's billions of neurons also are developed by the second trimester.[34]:100 Babies are hence born with some odor, taste and sound preferences, largely related to the mother's environment.[34]:101
Some primitive reflexes too arise before birth and are still present in newborns. One hypothesis is that these reflexes are vestigial and have limited use in early human life. Piaget's theory of cognitive development suggested that some early reflexes are building blocks for infant sensorimotor development. For example the tonic neck reflex may help development by bringing objects into the infant's field of view.[41]
Other reflexes, such as the walking reflex appear to be replaced by more sophisticated voluntary control later in infancy. This may be because the infant gains too much weight after birth to be strong enough to use the reflex, or because the reflex and subsequent development are functionally different.[42] It has also been suggested that some reflexes (for example the moro and walking reflexes) are predominantly adaptations to life in the womb with little connection to early infant development.[41] Primitive reflexes reappear in adults under certain conditions, such as neurological conditions like dementia or traumatic lesions.
Ultrasound has shown that infants are capable of a range of movements in the womb, many of which appear to be more than simple reflexes.[42] By the time they are born, infants can recognize and have a preference for their mother's voice suggesting some pre-natal development of auditory perception.[42] Pre-natal development and birth complications may also be connected to neurodevelopmental disorders, for example in schizophrenia. With the advent of cognitive neuroscience, embryology and the neuroscience of pre-natal development is of increasing interest to developmental psychology research.
Several environmental agents—teratogens—can cause damage during the prenatal period. These include prescription and nonprescription drugs, illegal drugs, tobacco, alcohol, environmental pollutants, infectious disease agents such as the rubella virus and the toxoplasmosis bacterium, maternal malnutrition, maternal emotional stress, and Rh factor blood incompatibility between mother and child.
Infancy
From birth until the first year, the child is referred to as an infant.[34] Developmental psychologists vary widely in their assessment of infant psychology, and the influence the outside world has upon it, but certain aspects are relatively clear.
The majority of a newborn infant's time is spent in sleep. At first this sleep is evenly spread throughout the day and night, but after a couple of months, infants generally become diurnal.
Infants can be seen to have six states, grouped into pairs:
quiet sleep and active sleep (dreaming, when REM sleep occurs)
quiet waking, and active waking
fussing and crying
Infant Perception: Infant perception is what a newborn can see, hear, smell, taste, and touch. These five features are better known as one's “five senses”.[43] Infants respond to stimuli differently in these different states.[42]
Vision is significantly worse in infants than in older children. Infant sight tends to be blurry in early stages but improves over time. Color perception similar to that seen in adults has been demonstrated in infants as young as four months, using habituation methods.[41] Infants get to adult-like vision in about six months.[34]:191
Hearing is well-developed prior to birth, unlike vision. Newborns prefer complex sounds to pure tones, human speech to other sounds, mother's voice to other voices, and the native language to other languages. Scientist believe these features are probably learned in the womb.[34]:151 Infants are fairly good at detecting the direction a sound comes from, and by 18 months their hearing ability is approximately equal an adult's.
Smell and taste are present, with infants showing different expressions of disgust or pleasure when presented with pleasant odors (honey, milk, etc.) or unpleasant odors (rotten egg) and tastes (e.g. sour taste). Newborns are born with odor and taste preferences acquired in the womb from the smell and taste of amniotic fluid, in turn influenced by what the mother eats. Both breast- and bottle-fed babies around 3 days old prefer the smell of human milk to that of formula, indicating an innate preference.[34]:150 There is good evidence for older infants preferring the smell of their mother to that of others.[41]
Touch and feel is one of the better-developed senses at birth considering it's one of the first senses to develop inside the womb.[44] This is evidenced by the primitive reflexes described above, and the relatively advanced development of the somatosensory cortex.[45]
Pain: Infants feel pain similarly, if not more strongly than older children but pain-relief in infants has not received so much attention as an area of research.[46]
Language: Babies are born with the ability to discriminate virtually all sounds of all human languages.[34]:189 Infants of around six months can differentiate between phonemes in their own language, but not between similar phonemes in another language. At this stage infants also start to babble, producing phonemes.
Infant Cognition: The Piagetian Era An early theory of infant development was the Sensorimotor stage of Piaget's Theory of cognitive development. Piaget suggested that an infant's perception and understanding of the world depended on their motor development, which was required for the infant to link visual, tactile and motor representations of objects. According to this view, it is through touching and handling objects that infants develop object permanence, the understanding that objects are solid, permanent, and continue to exist when out of sight.[42]
Special methods are used in the psychological study of infants.
Piaget's Sensorimotor Stage comprised six sub-stages (see sensorimotor stages for more detail). In the early stages, development arises out of movements caused by primitive reflexes.[47] Discovery of new behaviors results from classical and operant conditioning, and the formation of habits.[47] From eight months the infant is able to uncover a hidden object but will persevere when the object is moved.
Piaget came to his conclusion that infants lacked a complete understanding of object permanence before 18 months after observing infants' failure before this age to look for an object where it was last seen. Instead infants continue to look for an object where it was first seen, committing the "A-not-B error." Some researchers have suggested that before the age of eight to nine months, infants' inability to understand object permanence extends to people, which explains why infants at this age do not cry when their mothers are gone ("Out of sight, out of mind").
Recent Finding in Infant Cognition In the 1980s and 1990s, researchers have developed many new methods of assessing infants' understanding of the world with far more precision and subtlety than Piaget was able to do in his time. Since then, many studies based on these methods suggest that young infants understand far more about the world than first thought.
Based on recent findings, some researchers (such as Elizabeth Spelke and Renee Baillargeon) have proposed that an understanding of object permanence is not learned at all, but rather comprises part of the innate cognitive capacities of our species.
Other research has suggested that young infants in their first six months of life may possess an understanding of numerous aspects of the world around them, including:
- an early numerical cognition, that is, an ability to represent number and even compute the outcomes of addition and subtraction operations;[48]
- an ability to infer the goals of people in their environment;[49]
- an ability to engage in simple causal reasoning.[50]
Critical periods of development
There are critical periods in infancy and childhood during which development of certain perceptual, sensorimotor, social and language systems depends crucially on environmental stimulation.[51] Feral children such as Genie, deprived of adequate stimulation, fail to acquire important skills and are unable to learn in later childhood. The concept of critical periods is also well-established in neurophysiology, from the work of Hubel and Wiesel among others.
Developmental Delays
Children with developmental delays (DD) are at heightened risk for developing clinically significant behavioral and emotional difficulties as compared to children with typical development (TD). However, nearly all studies comparing psychopathology in youth with DD employ TD control groups of the same chronological age (CA).This comorbidity of DD and a mental disorder is often referred to as dual diagnosis. Epidemiological studies indicate that 30–50% of youth with DD meet the clinical cutoff for behavioral and emotional problems and/or diagnosable mental disorder. Studies that include comparison samples of children with typical development (TD) highlight the considerable difference in risk for psychopathology, with the relative risk for youth with DD (to youth with TD) ranging from 2.8–4.1 to 1.[52]
Toddlerhood
Infants shift between ages of one and two to a developmental stage known as toddlerhood. In this stage, an infant’s transition into toddlerhood is highlighted through self-awareness, developing maturity in language use, and presence of memory and imagination.
During toddlerhood, babies begin learning how to walk, talk, and make decisions for themselves. An important characteristic of this age period is the development of language, where children are learning how to communicate and express their emotions and desires through the use of vocal sounds, babbling, and eventually words.[53] Self-control also begins to develop. At this age, children take initiative to explore, experiment, and learn from making mistakes. Caretakers who encourage toddlers to try new things and test their limits, help the child become autonomous, self-reliant, and confident.[54] If the caretaker is overprotective or disapproving of independent actions, the toddler may begin to doubt their abilities and feel ashamed of the desire for independence. The child's autonomic development is inhibited, leaving them less prepared to deal with the world in the future. Toddlers also begin to identify themselves in gender roles, acting according to their perception of what a man or woman should do.[55]
Socially, the period of toddlerhood is commonly called the "terrible twos".[56] Toddlers often use their new-found language abilities to voice their desires, but are often misunderstood by parents due to their language skills just beginning to develop. A person at this stage testing their independence is another reason behind the stage’s infamous label. Tantrums in a fit of frustration are also common.
Early childhood
Also called "pre-school age," "exploratory age" and "toy age."
When children attend preschool, they broaden their social horizons and become more engaged with those around them. Impulses are channeled into fantasies, which leaves the task of the caretaker to balance eagerness for pursuing adventure, creativity and self-expression with the development of responsibility. If caretakers are properly encouraging and consistently disciplinary, children are more likely to develop positive self-esteem while becoming more responsible, and will follow through on assigned activities.
As children grow their past experiences will shape who they are, allow them to perceive the world in their own way. It helps a person go through everyday life.[57] If not allowed to decide which activities to perform, children may begin to feel guilt upon contemplating taking initiative. This negative association with independence will lead them to let others make decisions in place of them.
During a child's preschool and beginning school years, intelligence is demonstrated through logical and systematic manipulation of symbols related to concrete objects. Operational thinking develops, which means actions are reversible, and egocentric thought diminishes.
Children go through the transition from the world at home to that of school and peers. Children learn to make things, use tools, and acquire the skills to be a worker and a potential provider. Children can now receive feedback from outsiders about their accomplishments.
If children can discover pleasure in their activities, including their intellectual stimulation, most importantly in learning reading, writing, and basic math, they will develop a sense of competence. If they are not successful or cannot discover pleasure in the process, they may develop a sense of inferiority and feelings of inadequacy that may haunt them throughout life. This is when children think of themselves as industrious or as inferior.
Adolescence
Adolescence is the period of life between the onset of puberty and the full commitment to an adult social role, such as worker, parent, and/or citizen. It is the period known for the formation of personal and social identity (see Erik Erikson) and the discovery of moral purpose (see William Damon). Intelligence is demonstrated through the logical use of symbols related to abstract concepts and formal reasoning. A return to egocentric thought often occurs early in the period. Only 35% develop the capacity to reason formally during adolescence or adulthood. (Huitt, W. and Hummel, J. January 1998)[58]
It is divided into three parts namely:
Early Adolescence: 9 to 13 years (preteen),
Mid Adolescence: 13 to 15 years and
Late Adolescence: 15 to 18 years
The adolescent unconsciously explores questions such as "Who am I? Who do I want to be?" Like toddlers, adolescents must explore, test limits, become autonomous, and commit to an identity, or sense of self. Different roles, behaviors and ideologies must be tried out to select an identity. Role confusion and inability to choose vocation can result from a failure to achieve a sense of identity through, for example, friends.
Early adulthood
Early adulthood, according to theorists such as Erik Erikson, is a stage where development is mainly focused on maintaining relationships.[59] Examples include creating bond of intimacy, sustaining friendships, and ultimately making a family. Some theorists state that development of intimacy skills rely on the resolution of previous developmental stages. A sense of identity gained in the previous stages is also necessary for intimacy to develop. If this skill is not learned the alternative is alienation, isolation, a fear of commitment, and the inability to depend on others.
A related framework for studying this part of the life span is that of emerging adulthood. Scholars of emerging adulthood, such as Jeffrey Arnett, are not necessarily interested in relationship development. Instead, this concept suggests that people transition after their teenage years into a period not characterized as relationship building and an overall sense of constancy with life, but with years of living with parents, phases of self-discovery, and experimentation.[60]
Middle adulthood
Middle adulthood generally refers to the period between ages 25 to 69. During this period, middle-aged adults experience a conflict between generativity and stagnation. They may either feel a sense of contributing to society, the next generation or their immediate community or a sense of purposelessness.
Physically, the middle-aged experience a decline in muscular strength, reaction time, sensory keenness, and cardiac output. Also, women experience menopause and a sharp drop in the hormone estrogen. Men experience an equivalent endocrine system event to menopause. Andropause in males is a hormone fluctuation with physical and psychological effects that can be similar to those seen in menopausal females. As men age, lowered testosterone levels can contribute to mood swings and a decline in sperm count. Sexual responsiveness can also be affected, including delays in erection and longer periods of penile stimulation required to achieve ejaculation.
Old age
This stage generally refers to those aged over 70 .[citation needed] According to Erikson's Theory of Psychosocial Development, old age is the stage in which individuals assess the quality of their lives. In reflecting on their lives, people in this age group develop a feeling of integrity if deciding that their lives were successful or a feeling of despair if evaluation of one's life indicates a failure to achieve goals.[61]
Physically, older people experience a decline in muscular strength, reaction time, stamina, hearing, distance perception, and the sense of smell.[62] They also are more susceptible to diseases such as cancer and pneumonia due to a weakened immune system .[citation needed] Programs aimed at balance, muscle strength, and mobility have been shown to reduce disability among mildly (but not more severely) disabled elderly.[63]
Sexual expression depends in large part upon the emotional and physical health of the individual. Many older adults continue to be sexually active and satisfied with their sexual activity.[64]
Mental disintegration may also occur, leading to dementia or ailments such as Alzheimer's disease. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age.[65] Whether or not normal intelligence increases or decreases with age depends on the measure and study. Longitudinal studies show that speed declines .[citation needed] Some cross-sectional studies suggest that intellect is stable .
http://en.wikipedia.org/wiki/Developmental_psychology
Pre-natal development is of interest to psychologists investigating the context of early psychological development. The whole prenatal development involves three main stages: germinal stage, embryonic stage and fetal stage. Germinal stage begins at conception until 2 weeks; embryonic stage means the development from 2 weeks to 8 weeks; fetal stage represents 9 weeks until birth of the baby.[40] The senses develop in the womb itself: a fetus can both see and hear by the second trimester (13 to 24 weeks of age). Sense of touch develops in the embryonic stage (5 to 8 weeks).[34]:97 Most of the brain's billions of neurons also are developed by the second trimester.[34]:100 Babies are hence born with some odor, taste and sound preferences, largely related to the mother's environment.[34]:101
Some primitive reflexes too arise before birth and are still present in newborns. One hypothesis is that these reflexes are vestigial and have limited use in early human life. Piaget's theory of cognitive development suggested that some early reflexes are building blocks for infant sensorimotor development. For example the tonic neck reflex may help development by bringing objects into the infant's field of view.[41]
Other reflexes, such as the walking reflex appear to be replaced by more sophisticated voluntary control later in infancy. This may be because the infant gains too much weight after birth to be strong enough to use the reflex, or because the reflex and subsequent development are functionally different.[42] It has also been suggested that some reflexes (for example the moro and walking reflexes) are predominantly adaptations to life in the womb with little connection to early infant development.[41] Primitive reflexes reappear in adults under certain conditions, such as neurological conditions like dementia or traumatic lesions.
Ultrasound has shown that infants are capable of a range of movements in the womb, many of which appear to be more than simple reflexes.[42] By the time they are born, infants can recognize and have a preference for their mother's voice suggesting some pre-natal development of auditory perception.[42] Pre-natal development and birth complications may also be connected to neurodevelopmental disorders, for example in schizophrenia. With the advent of cognitive neuroscience, embryology and the neuroscience of pre-natal development is of increasing interest to developmental psychology research.
Several environmental agents—teratogens—can cause damage during the prenatal period. These include prescription and nonprescription drugs, illegal drugs, tobacco, alcohol, environmental pollutants, infectious disease agents such as the rubella virus and the toxoplasmosis bacterium, maternal malnutrition, maternal emotional stress, and Rh factor blood incompatibility between mother and child.
Infancy
From birth until the first year, the child is referred to as an infant.[34] Developmental psychologists vary widely in their assessment of infant psychology, and the influence the outside world has upon it, but certain aspects are relatively clear.
The majority of a newborn infant's time is spent in sleep. At first this sleep is evenly spread throughout the day and night, but after a couple of months, infants generally become diurnal.
Infants can be seen to have six states, grouped into pairs:
quiet sleep and active sleep (dreaming, when REM sleep occurs)
quiet waking, and active waking
fussing and crying
Infant Perception: Infant perception is what a newborn can see, hear, smell, taste, and touch. These five features are better known as one's “five senses”.[43] Infants respond to stimuli differently in these different states.[42]
Vision is significantly worse in infants than in older children. Infant sight tends to be blurry in early stages but improves over time. Color perception similar to that seen in adults has been demonstrated in infants as young as four months, using habituation methods.[41] Infants get to adult-like vision in about six months.[34]:191
Hearing is well-developed prior to birth, unlike vision. Newborns prefer complex sounds to pure tones, human speech to other sounds, mother's voice to other voices, and the native language to other languages. Scientist believe these features are probably learned in the womb.[34]:151 Infants are fairly good at detecting the direction a sound comes from, and by 18 months their hearing ability is approximately equal an adult's.
Smell and taste are present, with infants showing different expressions of disgust or pleasure when presented with pleasant odors (honey, milk, etc.) or unpleasant odors (rotten egg) and tastes (e.g. sour taste). Newborns are born with odor and taste preferences acquired in the womb from the smell and taste of amniotic fluid, in turn influenced by what the mother eats. Both breast- and bottle-fed babies around 3 days old prefer the smell of human milk to that of formula, indicating an innate preference.[34]:150 There is good evidence for older infants preferring the smell of their mother to that of others.[41]
Touch and feel is one of the better-developed senses at birth considering it's one of the first senses to develop inside the womb.[44] This is evidenced by the primitive reflexes described above, and the relatively advanced development of the somatosensory cortex.[45]
Pain: Infants feel pain similarly, if not more strongly than older children but pain-relief in infants has not received so much attention as an area of research.[46]
Language: Babies are born with the ability to discriminate virtually all sounds of all human languages.[34]:189 Infants of around six months can differentiate between phonemes in their own language, but not between similar phonemes in another language. At this stage infants also start to babble, producing phonemes.
Infant Cognition: The Piagetian Era An early theory of infant development was the Sensorimotor stage of Piaget's Theory of cognitive development. Piaget suggested that an infant's perception and understanding of the world depended on their motor development, which was required for the infant to link visual, tactile and motor representations of objects. According to this view, it is through touching and handling objects that infants develop object permanence, the understanding that objects are solid, permanent, and continue to exist when out of sight.[42]
Special methods are used in the psychological study of infants.
Piaget's Sensorimotor Stage comprised six sub-stages (see sensorimotor stages for more detail). In the early stages, development arises out of movements caused by primitive reflexes.[47] Discovery of new behaviors results from classical and operant conditioning, and the formation of habits.[47] From eight months the infant is able to uncover a hidden object but will persevere when the object is moved.
Piaget came to his conclusion that infants lacked a complete understanding of object permanence before 18 months after observing infants' failure before this age to look for an object where it was last seen. Instead infants continue to look for an object where it was first seen, committing the "A-not-B error." Some researchers have suggested that before the age of eight to nine months, infants' inability to understand object permanence extends to people, which explains why infants at this age do not cry when their mothers are gone ("Out of sight, out of mind").
Recent Finding in Infant Cognition In the 1980s and 1990s, researchers have developed many new methods of assessing infants' understanding of the world with far more precision and subtlety than Piaget was able to do in his time. Since then, many studies based on these methods suggest that young infants understand far more about the world than first thought.
Based on recent findings, some researchers (such as Elizabeth Spelke and Renee Baillargeon) have proposed that an understanding of object permanence is not learned at all, but rather comprises part of the innate cognitive capacities of our species.
Other research has suggested that young infants in their first six months of life may possess an understanding of numerous aspects of the world around them, including:
- an early numerical cognition, that is, an ability to represent number and even compute the outcomes of addition and subtraction operations;[48]
- an ability to infer the goals of people in their environment;[49]
- an ability to engage in simple causal reasoning.[50]
Critical periods of development
There are critical periods in infancy and childhood during which development of certain perceptual, sensorimotor, social and language systems depends crucially on environmental stimulation.[51] Feral children such as Genie, deprived of adequate stimulation, fail to acquire important skills and are unable to learn in later childhood. The concept of critical periods is also well-established in neurophysiology, from the work of Hubel and Wiesel among others.
Developmental Delays
Children with developmental delays (DD) are at heightened risk for developing clinically significant behavioral and emotional difficulties as compared to children with typical development (TD). However, nearly all studies comparing psychopathology in youth with DD employ TD control groups of the same chronological age (CA).This comorbidity of DD and a mental disorder is often referred to as dual diagnosis. Epidemiological studies indicate that 30–50% of youth with DD meet the clinical cutoff for behavioral and emotional problems and/or diagnosable mental disorder. Studies that include comparison samples of children with typical development (TD) highlight the considerable difference in risk for psychopathology, with the relative risk for youth with DD (to youth with TD) ranging from 2.8–4.1 to 1.[52]
Toddlerhood
Infants shift between ages of one and two to a developmental stage known as toddlerhood. In this stage, an infant’s transition into toddlerhood is highlighted through self-awareness, developing maturity in language use, and presence of memory and imagination.
During toddlerhood, babies begin learning how to walk, talk, and make decisions for themselves. An important characteristic of this age period is the development of language, where children are learning how to communicate and express their emotions and desires through the use of vocal sounds, babbling, and eventually words.[53] Self-control also begins to develop. At this age, children take initiative to explore, experiment, and learn from making mistakes. Caretakers who encourage toddlers to try new things and test their limits, help the child become autonomous, self-reliant, and confident.[54] If the caretaker is overprotective or disapproving of independent actions, the toddler may begin to doubt their abilities and feel ashamed of the desire for independence. The child's autonomic development is inhibited, leaving them less prepared to deal with the world in the future. Toddlers also begin to identify themselves in gender roles, acting according to their perception of what a man or woman should do.[55]
Socially, the period of toddlerhood is commonly called the "terrible twos".[56] Toddlers often use their new-found language abilities to voice their desires, but are often misunderstood by parents due to their language skills just beginning to develop. A person at this stage testing their independence is another reason behind the stage’s infamous label. Tantrums in a fit of frustration are also common.
Early childhood
Also called "pre-school age," "exploratory age" and "toy age."
When children attend preschool, they broaden their social horizons and become more engaged with those around them. Impulses are channeled into fantasies, which leaves the task of the caretaker to balance eagerness for pursuing adventure, creativity and self-expression with the development of responsibility. If caretakers are properly encouraging and consistently disciplinary, children are more likely to develop positive self-esteem while becoming more responsible, and will follow through on assigned activities.
As children grow their past experiences will shape who they are, allow them to perceive the world in their own way. It helps a person go through everyday life.[57] If not allowed to decide which activities to perform, children may begin to feel guilt upon contemplating taking initiative. This negative association with independence will lead them to let others make decisions in place of them.
During a child's preschool and beginning school years, intelligence is demonstrated through logical and systematic manipulation of symbols related to concrete objects. Operational thinking develops, which means actions are reversible, and egocentric thought diminishes.
Children go through the transition from the world at home to that of school and peers. Children learn to make things, use tools, and acquire the skills to be a worker and a potential provider. Children can now receive feedback from outsiders about their accomplishments.
If children can discover pleasure in their activities, including their intellectual stimulation, most importantly in learning reading, writing, and basic math, they will develop a sense of competence. If they are not successful or cannot discover pleasure in the process, they may develop a sense of inferiority and feelings of inadequacy that may haunt them throughout life. This is when children think of themselves as industrious or as inferior.
Adolescence
Adolescence is the period of life between the onset of puberty and the full commitment to an adult social role, such as worker, parent, and/or citizen. It is the period known for the formation of personal and social identity (see Erik Erikson) and the discovery of moral purpose (see William Damon). Intelligence is demonstrated through the logical use of symbols related to abstract concepts and formal reasoning. A return to egocentric thought often occurs early in the period. Only 35% develop the capacity to reason formally during adolescence or adulthood. (Huitt, W. and Hummel, J. January 1998)[58]
It is divided into three parts namely:
Early Adolescence: 9 to 13 years (preteen),
Mid Adolescence: 13 to 15 years and
Late Adolescence: 15 to 18 years
The adolescent unconsciously explores questions such as "Who am I? Who do I want to be?" Like toddlers, adolescents must explore, test limits, become autonomous, and commit to an identity, or sense of self. Different roles, behaviors and ideologies must be tried out to select an identity. Role confusion and inability to choose vocation can result from a failure to achieve a sense of identity through, for example, friends.
Early adulthood
Early adulthood, according to theorists such as Erik Erikson, is a stage where development is mainly focused on maintaining relationships.[59] Examples include creating bond of intimacy, sustaining friendships, and ultimately making a family. Some theorists state that development of intimacy skills rely on the resolution of previous developmental stages. A sense of identity gained in the previous stages is also necessary for intimacy to develop. If this skill is not learned the alternative is alienation, isolation, a fear of commitment, and the inability to depend on others.
A related framework for studying this part of the life span is that of emerging adulthood. Scholars of emerging adulthood, such as Jeffrey Arnett, are not necessarily interested in relationship development. Instead, this concept suggests that people transition after their teenage years into a period not characterized as relationship building and an overall sense of constancy with life, but with years of living with parents, phases of self-discovery, and experimentation.[60]
Middle adulthood
Middle adulthood generally refers to the period between ages 25 to 69. During this period, middle-aged adults experience a conflict between generativity and stagnation. They may either feel a sense of contributing to society, the next generation or their immediate community or a sense of purposelessness.
Physically, the middle-aged experience a decline in muscular strength, reaction time, sensory keenness, and cardiac output. Also, women experience menopause and a sharp drop in the hormone estrogen. Men experience an equivalent endocrine system event to menopause. Andropause in males is a hormone fluctuation with physical and psychological effects that can be similar to those seen in menopausal females. As men age, lowered testosterone levels can contribute to mood swings and a decline in sperm count. Sexual responsiveness can also be affected, including delays in erection and longer periods of penile stimulation required to achieve ejaculation.
Old age
This stage generally refers to those aged over 70 .[citation needed] According to Erikson's Theory of Psychosocial Development, old age is the stage in which individuals assess the quality of their lives. In reflecting on their lives, people in this age group develop a feeling of integrity if deciding that their lives were successful or a feeling of despair if evaluation of one's life indicates a failure to achieve goals.[61]
Physically, older people experience a decline in muscular strength, reaction time, stamina, hearing, distance perception, and the sense of smell.[62] They also are more susceptible to diseases such as cancer and pneumonia due to a weakened immune system .[citation needed] Programs aimed at balance, muscle strength, and mobility have been shown to reduce disability among mildly (but not more severely) disabled elderly.[63]
Sexual expression depends in large part upon the emotional and physical health of the individual. Many older adults continue to be sexually active and satisfied with their sexual activity.[64]
Mental disintegration may also occur, leading to dementia or ailments such as Alzheimer's disease. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age.[65] Whether or not normal intelligence increases or decreases with age depends on the measure and study. Longitudinal studies show that speed declines .[citation needed] Some cross-sectional studies suggest that intellect is stable .
http://en.wikipedia.org/wiki/Developmental_psychology