What were you like when you were six years old? What was your favorite toy or your favorite food? Are you the same as you were then, or have you changed a lot? From the very beginning of life, all the way until the very end, humans are constantly changing.
- What is lifespan development in psychology?
- What is the average human lifespan?
- How do researchers study the human lifespan?
- What are the lifespan stages of human development?
- What are some lifespan theories of human development in psychology?
Understanding Lifespan Development
How people change over time throughout their lives is called lifespan development. They change in different ways: physically, cognitively, socially, emotionally, and morally. There is an ongoing debate about how humans develop. Is it because of genes or their upbringing? This concept is the root of nature vs. nurture, the two main parts of the whole development of a person.
Nature: the genes, inherited traits, and other hereditary factors passed on from parent to offspring.
Nurture: upbringing, environmental factors, place in society, and cultural forces that influence an individual.
There are many theories about how humans develop. Some theories adhere to the concept of continuity, and others say that development is more about discontinuity.
Continuity: the constant process of development. It is the idea that human development is fluid or continuous and is not defined by huge changes or crises.
Discontinuity: the idea that, in human development, each stage of life comprises a series of tasks or skills to complete before progressing to the next developmental stage.
According to these viewpoints, each person goes through the same steps in the same order but at different speeds.
Continuity: Jane moves from first grade to second grade to third grade without any major difficulties or problems. She does well in each grade, learns what she needs to learn, and moves on to the next grade.
Discontinuity: Billy struggles to learn how to read and write. Once he finally is able to read and write well, he struggles in math. Once he feels like he is doing well in math, he struggles to understand politics and remember historical facts. Each stage is a crisis or task that Billy has to complete before moving on to the next.
The stability vs. change argument is about whether a person stays the same from childhood to adulthood (stability) or changes as a result of developing and evolving throughout the lifespan (change). Stability is the idea that people generally remain the same throughout life. Their personal qualities in childhood indicate what qualities they will continue to have later in life.
Change is the idea that personal qualities and personality traits can change due to various social interactions, life experiences, and cultural adjustments. Change is related to the concept of brain plasticity. The brain forms new connections and prunes old ones based on which connections are used and which ones are not.
Stability: Peter was really loud and active as a kid. As an adult, he's still loud and active. He uses his loudness and activity in different ways as an adult than as a kid, but these personal characteristics have remained the same.
Change: Emma was quiet and shy as a little girl, but now she's outgoing and expressive. She learned as a child that it's hard to make friends if you stay quiet and shy, so she began changing these behaviors.
Fig. 1 Continuity and discontinuity, Pixabay.
Average Human Lifespan
Throughout history, many researchers have studied the average human lifespan as well as factors that affect lifespan health. There are many biological (e.g. genes) and environmental factors (e.g. living conditions, access to healthcare, or lifestyle) that can impact a person's aging and overall life expectancy. It is easy to confuse the terms life expectancy and lifespan. Despite their similarities, these are two separate concepts.
Life expectancy: the number of years a person is expected to live. It differs from one person to another based on factors like age, diet, medical history, heredity, gender, and lifestyle.
Lifespan: the maximum number of years a person can live without any personal or environmental enhancements.
The average human lifespan in 2019 is 73 years old, up from 67 years old in 2000. In view of the global health situation, there is an overall increasing trend in longevity (WHO, 2020 as cited in Mangan, 2022)1. The average lifespan in the United States is around 78 years old (Shealy, 2009)2.
According to Shealy (2009)2, it would appear that the factors that contribute to a shorter lifespan in the United States are smoking (seven years), obesity (seven years), poor diet (three to four years), and a lack of physical activity (three to four years).
Studying the Lifespan of Humans
Lifespan in developmental psychology involves the study of an individual's development over the course of their life as they age. It is related to the study of evolution and life factors that affect the growth and aging process. There are multiple ways that researchers study the human lifespan.
Longitudinal Research
This method allows the continual measurement of individual development differences within a defined timetable. Participants in this kind of study are all the same age and have long-term contact with the researchers, which might last months or years. Longitudinal studies help determine stability and change across time.
Cross-Sectional Research
This strategy entails collecting data from people of various ages simultaneously. Cross-sectional studies are beneficial for comparing features among people of different ages in a community or obtaining data for future studies and research. This research method is less time-consuming than longitudinal research because no participant follow-up is required. It is also less costly.
Cohort-Sequential Research
Cohort-sequential research combines longitudinal and cross-sectional analysis. It involves the study and follow-up of participants through time within groups based on age. This method allows researchers to look at individual changes across time compared to others of different ages and times in history. The researchers can determine if development occurs differently across different ages at the same time interval and check for distinctions due to being born within a specific time period.
Retrospective Research
In retrospective research, participants give information about their past and other important data relevant to the study. Data gathering includes interviews, questionnaires, or medical records.
Fig. 2 Young to old, Pixabay.
Lifespan: Human Development Stages
There are different ways to categorize the stages of human development, but one common way is in eight stages, from prenatal to late adulthood.
Prenatal Stage: This is the stage in which a fertilized egg develops inside the womb.
Infancy and Toddler Stage: from birth to three years of age. This stage displays rapid changes in different areas, including physical, socio-emotional, language, and cognitive development. Completing milestones helps lay the foundation for independence and a healthy sense of self.
Early Childhood Stage: the preschool years from birth to six years old. Experts say that this phase is crucial in human development since it can determine overall life outcomes.
Middle Childhood Stage: Children between the ages of six to 12 display greater control and mastery of body movements and motor skills. They learn how to reason better and adapt their thoughts to different situations.
Adolescent Stage:Adolescence is a phase of rapid physical and socio-emotional transformation brought about by puberty. Also called the "teenager phase" between the ages of 13 to 19 years, the adolescent stage is defined as the transition from childhood to adulthood.
Early Adulthood Stage: Early adulthood typically spans from ages 20 to 35, where individuals explore open doors in many areas of life such as career, romance, building families, and forming close relationships. It is also the stage where humans achieve milestones in independence as they venture out in life, seeking to make their own choices.
Middle Adulthood Stage: Middle adulthood is generally defined as ages 35 to 65. Some key features of this phase include maintaining stability in relationships, careers, hobbies, parenting, and preparation for late adulthood. Most people experience love and work at their peak during this stage. Signs of aging also become more apparent such as graying hair, muscle loss, visual changes, and hearing problems.
Late Adulthood Stage: the ages of 65 to the very last year of life. This stage can reach up to 120 years for those who have a longer lifespan. The late adulthood stage has features of physical decline due to aging and a host of emotions about death and dying. Aside from these changes, this period is also marked by a decrease in cognitive abilities, affecting short-term memory and the ability to acquire new information.
Fig. 3 Human development over time, Pixabay.Human Development Across the Lifespan
There are many different ways to consider how humans develop, but there are a few key ideas in developmental psychology that help us understand this better. They are maturation, assimilation, accommodation, and critical periods in development.
Maturation
Maturation is a natural physical and mental development process that occurs over time until a person reaches full maturity. Maturity, in this sense, can also mean when a person starts to act like a grown-up. One example of this is when a person seeks emotional stability, which is a sign of maturity.
During a child's life, maturation also involves learning and body movements, including gross and fine motor skills. Maturation is also essential in learning as certain maturity levels indicate readiness to acquire new knowledge and skills.
Assimilation and Accommodation
Assimilation and accommodation are about cognitively organizing information as you learn and grow.
When a child sees a dog for the first time, the child learns that a dog has four legs and a tail. This is the child's dog schema. A schema is a collection of information that provides a framework for organizing and acquiring new knowledge.
If the same child sees a horse during his first time visiting the zoo, the child might call it a dog, demonstrating assimilation. Assimilation is piecing new information into an old schema. In this case, the child puts the horse into the dog schema of an animal with four legs and a tail.
On the other hand, accommodation is creating space in a body of knowledge to insert new information. A child accommodates new words such as horse and cat and understands that not all animals with four legs and a tail are dogs. New schemas are created in the child's mind to organize this information. Assimilating involves using old knowledge to understand new situations, while accommodation involves redesigning old knowledge and understandings to include new knowledge.
Critical Periods in Development
A critical period applies to many vital areas in development, such as language, social interactions, hearing, and vision. Exposure to appropriate and specific influences significantly affects development during its critical periods. A critical period is a window of opportunity for optimal growth and proper functioning. If the right conditions are present, the individual will develop normally. If not, they will exhibit impairments in development.
Lifespan Theories in Psychology
There are many theories of development in psychology that touch on different aspects of life.
Psychosexual Theory of Development
Sigmund Freud introduced the Psychosexual Theory of Development. He believed that our personality is shaped by our experiences in early childhood and that there are certain fixations that happen during each stage: Oral, Anal, Phallic, Latency, and Genital. His theory is an example of discontinuity.
Ainsworth's Attachment Theory
Psychologist Mary Ainsworth built upon British psychologist John Bowlby's original study on attachment theory in her 1970s research. Ainsworth classified attachment into three types: secure attachment, ambivalent-insecure attachment, and avoidant-insecure attachment.
Erikson's Psychosocial Theory of Development
Erik Erikson introduced the Psychosocial Theory of Development as a modification of Sigmund Freud's Psychosexual Theory. He proposed that social connection throughout the lifespan fosters development. According to Erikson, each stage in life consists of certain tasks that must be completed, and the inability to do so elicits feelings of insufficiency.
The stages in Erikson's Psychosocial Theory include:
Trust vs. Mistrust (birth to 12 to 18 months).
Autonomy vs. Shame (18 months to 3 years).
Initiative vs. Guilt (3 to 6 years).
Industry vs. Inferiority (6 to 12 years).
Identity vs. Confusion (12 to 18 years).
Intimacy vs. Isolation (19 to 40 years).
Generativity vs. Stagnation (40 to 65 years).
Integrity vs. Despair (65 to death).
Cognitive Theory of Development
According to Piaget's Cognitive Theory of Development, children at a certain age process information differently. Piaget's stages in this theory include Sensorimotor, Preoperational, Concrete Operational, and Formal Operational. Each phase of development is focused on cognitive functions and language development.
Moral Theory of Development
Lawrence Kohlberg explored another aspect of human development. As Piaget focused on cognitive development, Kohlberg's primary area of study is how individuals process morality-based choices. His stage includes three levels of moral development:
Pre-conventional morality: obedience based on punishments and pursuits based on rewards
Conventional morality: morality based on social acceptance and conforming to societal expectations
Post-conventional morality: understanding of personal rights and universal principles of ethics
Carol Gilligan's Theory of Moral Development
This theory contends that men and women think differently, especially when it comes to moral issues. Gilligan's study on moral formation explains how relationships influence a woman's morality more than they do a man's. Gilligan thought that Kohlberg's phases of moral growth were too male-oriented. She believed that men are more logical and individualistic, and women focus more on personal interactions and taking care of others when making moral decisions.
Lifespan - Key takeaways
- Nature refers to inherited qualities and other hereditary factors, and nurture refers to one's upbringing and environmental factors that influence development.
- Continuity is the idea that human development is mostly fluid and not defined by huge changes or crises. Discontinuity is the concept that each stage serves as a series of tasks or skills that must be learned or acquired to progress to the next developmental stage.
- Stability is the idea that personality qualities present in childhood stay the same throughout life. Change is the idea that personality traits change due to various social interactions, life experiences, and cultural adjustments.
- The four human lifespan research methods are longitudinal, cross-sectional, cohort-sequential, and retrospective.
- The stages of human development are prenatal, infancy and toddlerhood, early childhood, middle childhood, adolescence, early adulthood, middle adulthood, and late adulthood.
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