What are the scope and methods of developmental psychology? - Chapter 1

Developmental psychology can be defined as the discipline that attempts to describe and explain the changes that are present in thoughts, behavior, reasoning and functioning in a person under the influence of biological, individual and environmental factors. Developmental psychologists study the development of children and in general people throughout life from different perspectives.


What is meant by studying changes with age?

The newborn infant is a helpless creature with limited means of communication and few skills. By 18 - 24 months (the end of the period of infancy) this has changed. The child has formed relationships with others, learned a lot about the world and is about to take major steps in language development. By the time of adolescence the child is mature: a conscious individual who actively tries to adapt to a rapidly changing and complex society. It is tempting to think that the child only develops because it gets older. Increasing in age, by itself, contributes nothing to development. It is the maturation and changes resulting from experience that allows an individual to go through the different stages of development. An example of this is puberty. Despite the fact that its onset can be influenced by environmental factors such as diet, the changes that occur are primarily genetically determined. However, it is always important to look at the various factors that influence the development as it takes place. 

Concepts of human development

The assumptions and ideas we have about human nature influence how we rear our own children and how we interpret the findings from studies of children. The 'folk' theories of development often reflect what psychologists investigate. The purpose of this is to put our understanding on a more scientific footing.

'Folk' theories of development: punishment or praise?

We all have ideas about how children should be raised. These ideas emerge from our own upbringing, our experience with peers, the ideas of our parents, the media and many other sources. These ideas often influence how we raise our own children and are often transferred from generation to generation. For example, there are various ways in which children can attach to their caregivers and these attachment styles are often continuous and stable within different generations. 

How can development be defined according to world views?

Psychologists and others who do research on the development of children have different views on this development. They also use different approaches. There are two different ways development is looked at. The way in which the world is viewed, also known as the paradigm, is a philosophical system of ideas that serves to order a set of scientific theories and associated scientific methods. Two different visions formulated by psychologists are an organismic worldview and a mechanistic world view.

Organismic world view

According to the organismic world view, a person is a biological organism that is naturally active and continuously interacts with the environment and thereby helps to shape its own development. This world view emphasizes the interaction between maturation and experience that leads to the development of new internal, psychological structures for processing input from the environment. An example of a theoretician who supported this world view is Piaget. He suggested that cognitive development takes place in different phases and that the reasoning of the child in a particular phase is qualitatively different in earlier and later phases. The goal of developmental psychologists within this worldview is to determine when different psychological phases are present and which variables, processes and / or laws determine the differences between phases and what makes the transition between them. 

Mechanistic world view

According to the mechanistic world view, a person can be looked at as if it was a machine (like a computer), which is naturally passive until it is stimulated by the environment. According to this view, human behavior can be traced back to habits that have been learned in the environment and through previous experiences. The frequency of behavior increases when someone gets older through different learning processes and they can become less when someone gets older when they are no longer functional or lead to negative consequences. Developmental psychologists study learning principles that determine the way in which an organism responds to stimulation and if that results in an increase, decrease or changes in behavior. According to this world view, the child is more passive rather than active in forming his own development. This worldview represents the vision of the behaviorists

How can development be studied?

Developmental psychologists have different strategies to investigate development. These different ways can be subdivided into two broad, interrelated categories. Designs that allow us to look at age-related changes in behavior and the associated research methods used to gather information about development. 

Cross-sectional designs

In a cross-sectional design, people of different ages are tested once, all at a different point on the x-axis. The x-axis is the horizontal axis of a graph and represents the age in years. This is the most widely used research method by development researchers because it takes the least amount of time and provides a quick approach to changes that occur as someone gets older. However, it only describes age differences. There is no way to indicate the continuity or discontinuity of different processes (such as personality stability, sudden changes in language development or production) because an average is taken of different individuals of the same age. 

Longitudinal designs

With a longitudinal design, people are tested several times as they age. This method is powerful because it looks at the individual development of a person at different moments, whereby one can look at changes within the individual and at differences between individuals. There are different types of longitudinal designs and they can be very time-consuming. Disadvantages of these designs are the costs. It can also be difficult to plan repetitive visits with the same children. Furthermore, there can be a lot of outage. If, for example, children who find a task difficult and stop participating in the study. Related to that there can be the case of selective survivorship, which means that the children who participate in the research are not a good representation of the children in a community, which makes the results less generalizable. Another big problem is the time it takes to complete a study. This also depends on the time frame that is being looked at. If, for example, the functioning of IQ testing between a person's 20 and 80 years of age is examined, it takes 60 years to complete a study. After all that work, it is still possible that the results only apply partly to the examined age cohorts. Finally, there may also be an effect of repeated testing: children who are repeatedly examined may become better at performing a task simply because they have more experience with this. As a result, the data may not be a good reflection of normal development if it is not practiced regularly. 

Microgenetic methods

A combination of procedures that are becoming increasingly popular are referred to as microgenetic methods. Developmental psychology is fundamentally concerned with change and its causes and consequences. However, much research only provides a snapshot of changes without describing the process of change itself. Microgenetic methods examine change as it occurs and involve individual children who are examined repeatedly, within a short period of time. This method offers detailed information about an individual or individuals over a period of transition. The information gathered can include theory of mind, memory, analogical reasoning, the use of strategies, conscious and unconscious processes etc. 

In general, researchers try to collect both longitudinal and cross-sectional data for a specific subject. We expect to get similar results and this is usually the case. However, this does not always happen and the two designs can sometimes give very different results. Two cases of conflicting results are discussed below. First, the length of time between the measurements is discussed and secondly, the cohort effects are examined. 

Time between measures

If a study is developed investigating development, it must be determined at which ages children are tested or how often tests are repeated. When testing children, it is normal to examine them monthly or biweekly within a longitudinal study, depending on what the expectation is that there will be a change in behavior. The transition point for changes in behavior depending on age can be estimated on the basis of cross-sectional data. While this is applicable in most cases, children are sometimes tested in different ages which can result in different developmental functions that are being calculated. An interesting example of this is physical growth, which is usually seen as a continuous, increasing growth curve. Research has shown, however, that in small children there can be a "growth burst" in which children suddenly grow an inch and then again don't grow for a period of time. 

Cohort effects

Another serious design problem, which is particularly relevant for studies looking at a large age range, concerns cohort effects. This means that there are changes within generations in a trait that is being researched. A cohort is a group of people who all share a common experience. For example: the average height of a Western 20-year-old man increased from 1.52m around 1900 to 1.83 meters around 2007. This is due to improvements in people's eating, which made life in the womb and afterwards became healthier. In addition, differences were observed in attitudes, leisure activities and everyday life. In terms of intelligence, it can also be stated that intelligence, as measured by IQ testing, has changed over the past years. 

Sequential designs

A possible way to investigate the different findings that may arise from longitudinal and cross-sectional designs are sequential or age cohort designs. These studies contain a combination of designs and are rather rare, mainly because they cost a lot of time and money. This design is explained on the basis of an example: the intelligence is measured by means of an intelligence test. Adults in five different age groups have done this test twice. For example, the cross-sectional and longitudinal part of the test is met. The results show two effects. There is a cohort effect resulting from testing different adults at different ages around the same time: older adults did less well. In addition, there is the longitudinal effect where it appears that the same individuals do better in the second test than in the first. So, IQ scores have shown growth in recent generations, a phenomenon better known as the Flynn effect. However, if the same individuals are tested for a longer period of time, their scores remain relatively stable. In other words, intelligence does not decrease as people get older, but the environment provides better scores for new generations. The Flynn effect will be further discussed later. 

Research methods

The just discussed designs are always provided with one or more research methods to investigate development. Developmental psychologists have developed different methods to do this, the most important of which are observational studies, experimental methods, psychological tests and correlational studies.

Observational studies

The simplest form of observational studies are case studies. This means that the same person is repeatedly observed. These observations are usually in children and are done by parents or carers who are close to the child. The diaries detailing an infant's development are called baby biographiesCase studies provide a lot of information and are a source of ideas and insights. However, they have many weaknesses and disadvantages. For example, it is difficult to generalize on the basis of what has been observed in one person. In addition, there is often no system in the observations and they are often only written down afterwards. However, there are also positive points to the case study. A detailed report can be made of small changes in the behavior because  the child is familiar.

Time sampling

Time sampling is an observation method in which individuals are observed for a certain period of time. During frequent intervals in this period, notes are made, generally by an observer but sometimes also by the person himself, whether certain behavior occurs or not. For example, a researcher can observe a child for 20 minutes and every 30 seconds for an interval of 5 seconds indicate whether a child plays with others, plays alone, does not play, is aggressive, etcetera. There was a study in which students were given a timer that went off seven times a day. At that moment the students had to indicate what they were doing and what their affect status was: whether they were angry, happy, etcetera. The purpose of time sampling is to get an idea of ​​how frequently different behavior occurs during the observed period. However, there are two limitations of this method. Firstly, the researcher may not get a clear picture of the amount of time spent on certain behavior, so there may be a lot of behavior that is not signaled at times that are not noted. In addition, many behaviors of interest may simply not occur or might be missed during the period that recording is taking place.

Event sampling 

An alternative method is event sampling. This method does not have the problems that occur with time sampling. It's a procedure whereby researchers actively select a certain event that they want to investigate. This event is then observed, usually during the entire time in which the event takes place (not in intervals) on a continuous basis. As a result, this way of observing is also called continuous sampling and is the most used observation method in research into the development of children. Although these methods resemble a longitudinal design, their goal is to collect data in a systematic way and not to observe change. 

The clinical method

The greatest developmental psychologist of all time, Jean Piaget, studied the development of his three children during their childhood. From his research the clinical method emerged. This is a combination of observation and a structured experiment. 

Experimental methods

The majority of studies on the behavior of children and their development are experimental. Behavior and development does not take place without a cause. The aim of the researcher is to demonstrate causal relationships between maturation, experience, learning and behavior. The essential aspect of experimental techniques is control. A situation has been constructed in which the researcher has control over the causal variables that influence the behavior that is being looked at. One of these factors is a constant factor, also known as the independent variable. The behavior that is measured is the dependent variable. If the research goes well, changes in the behavior (the dependent variable) are caused by the controlled factor (independent variable). An example of a research using this technique is a structured observation. In this research method, the independent variable is systematically checked and adjusted, whereby the researcher observes the child's behavior (in response to the variable). 

Psychological testing

Psychological tests can be defined as instruments for the quantitative assessment of a psychological characteristic (or characteristics) of a person. The developmental psychologist has several tests at his disposal to examine psychological functioning at different ages. This includes tests of motor development, personality development, motivation, reading, etcetera. Such tests are generally standardized on the basis of large samples of children in the right age groups, which allowed standards to be set for age and gender. 

Types of test items

The type of item included in a particular test depends on the age group it is intended for and what is being measured. Tests that do research into the development of children usually consist of an observation of the child when the child is confronted with different standard situations: they can stand alone, they can make a tower of 5 blocks, et cetera. When children are older than two, tests increasingly use language and give instructions to children in a verbal way. So in intelligence tests, children can be asked to solve problems, to give the meaning of words, et cetera. 

Can test scores predict later development?

Tests of ability and intelligence become increasingly accurate in predicting later behavior (for example, performing at school). However, attempts to predict the personality of an adult from personality research at a young age have not been very successful. There is a number of exceptions: children who are shy or bold are often also as adults. In addition, it has been shown that a child who fights with other children a lot is often also an adolescent who is judged by peers to be aggressive. Aggression is a personality trait which is seen as most continuous. However, personality is a term that is extremely difficult to define and personality traits are difficult to measure. A problem with measuring personality is that the most important personality traits, such as extraversion, introversion , socialableness, etcetera, are social in nature and can vary depending on the different environments in which individuals find themselves. So despite the fact that there seems to be some stability in, for example, shy or bold children, they can show different behavior in other social settings. In addition, personality development is influenced by life experiences: an adolescent will be treated differently than a child of 7 and this will affect the way the individual behaves and responds. 

Uses of tests

Developmental psychologists use many different tests. Tests are regularly used in clinical and educational assessments to gain insights into an individual child and to see how this child performs compared to children of the same age and gender. Another use is to select groups of children for participation in an experiment and then to evaluate the results of the experiment. In this research there is an experimental group, in which an experiment is performed to see what the effect is, and a control group in which no experiment is performed so that the results of both groups can be compared and to investigate if the experiment (for example a reading method) has been successful. 

Correlational studies

correlation coefficient is a statistical value between +1 and -1 that gives an indication of the extent to which two variables are related to each other. A value close to +1 is a high positive relationship, which means that the two variables are strongly related. An example of such a relationship is between weight and height: longer people often weigh more. In addition, there are also correlations close to 0 which indicates a minimal correlation. For example, length is not correlated to academic performance. A correlation coefficient close to -1 is a high negative correlation, which means that the variables are inversely correlated. There are not many examples of this correlation, a possible example could be the relationship between watching TV and school grades: the more television is watched, the lower the grades. There are generally two types of correlational studies that are important in developmental psychology: concurrent and predictive

Concurrent studies

In a concurrent correlational study, there is interest in the relationship between variables measured at the same time. An example of this is to examine how much the IQ scores of twins match. In this study intelligence tests are given to twins and if the correlation is high, this means that if the IQ of one is high, the IQ of the other is also high. 

Predictive studies

predictive correlational study is a study that is interested in finding whether individuals retain their relative standing, or rank order, relative to others, over time. For example: a smart child of 5 is also a smart person when he is 20. Correlation studies are important as they indicate which kind of properties or psychological characteristics generally go together (concurrent correlation) and which characteristics predict later behavior (predictive correlation). 

Neurodevelopmental studies

A challenging task for developmental psychologists is to understand brain development and the relationship between this development and the development of cognitive, social and motor skills. To do research on this, neuro-developmental studies are used which again use selective methods. An example of such a method is a marker task. This is a method that is designed to elicit behavior of which the neural basis is known. This neural basis is often discovered in research in animals. For example, much is known about the neural basis of vision by experimenting with monkeys. Research has shown that a specific part of the visual system called the medial temporal area (MT) in monkeys also works in the human brain and that development of this area and the relationships of this area to other brain areas is responsible for the onset of smooth pursuit. 

Imaging methods

There are different ways in which brain activity can be mapped in both animals and humans. These imaging methods can be subdivided into techniques that measure brain activity inside the head and techniques that measure activity from the scalp. Measurements from the scalp are done with electrodes that measure electrical activity produced by neurons. An example of this is an electroencephalogram (EEG). The EEG is usually performed if the brain activity is to be measured during a specific event, called an event-related potential (ERP). With this method it can be difficult to only look at specific brain areas because all activity is measured at the surface. In order to have access to deep structures such as the areas that deal with memory or emotion, this method is not very reliable. 

Two visual techniques are better to use when measuring cortical brain areas: positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). A PET scan works by measuring the blood flow in the body. The blood flow is followed to regions where there is a lot of activity. In the case of PET, the person must be injected with radioactive material which causes this method to be used minimally in children. The fMRI also measures blood flow but does not use radioactive material. A magnetic field is used. However, there are some disadvantages of fMRI: this method is very expensive and the person has to lie very still for a longer period of time. In addition, the magnetic field is produced by a device that makes a lot of noise. Little use is made of this method in very small children, but in children aged 5 years and older there is an increase in use. 

Psychologists have different research strategies and methods for observing, classifying, testing and studying the development of children. There are no fixed rules for determining which method should be used in a specific study and this decision will depend on different considerations, for example:

  • The problem that's being investigated. 
  • The availability of the participants. 
  • The individual preference of the researcher. 

As we have seen, observational studies are ideal for asking questions about the different phases and aspects of child development. Such studies can often lead to theories and they are important in drawing up a hypothesis about aspects of development. We must always remember that the child has a fixed repertoire of behaviors that occur in a natural setting. We can conclude that observational studies are perfect for studying the behavior and development of the child in the natural context. A frequently used argument against the use of experiments is that they often take place in a highly controlled and unnatural setting. While experimental studies tell a lot about behavior in such settings, it sometimes happens that experimental findings have little influence on events in real life. It is often stated that many experimental studies lack ecological validity. Nevertheless, much can be learned from experimental studies, even if the experimental setting is far from real life. It is also clear that observational studies are less powerful than experimental studies when it comes to understanding the causes of development or testing hypotheses. A well-controlled experiment allows us to make precise statements about cause and effect. The level of control required is often not easily obtained in a natural setting and experiments are often conducted in a laboratory. A laboratory often has no special characteristics in such a setting, it can be a quiet space in a school, for example, or it can be a room that has been designed with a purpose and where there are deliberately certain items. Experiments enable us to explore ways of research that can not easily be investigated by only using observations. 

What is the importance of research evidence?

Sometimes when psychologists publish their findings, there are remarks such as 'what a waste of money, everyone knows that people behave like that'. Such comments assume that general observations of behavior are an adequate replacement for controlled observations and experiments. However, observations made every day of human behavior and 'folk theories' about development are unreliable and in our impressions and interpretations of behavior we are often unaware of the controlling and causative variables. In addition, there are often different contradictory 'assumptions' of people about behavior and development. Good research is needed to choose which assumption is the 'right' one or to show that all assumptions are not correct. An example of an assumption that is not true is the catharsis hypothesis. This hypothesis states that watching aggressive tendencies in others will reduce our own feelings of aggression. However, research has shown that watching aggression rather increases the aggression in children than to decrease it. 

Social policy implications of child development research

In the last part of the twentieth century and at the beginning of the twenty-first century, researchers have applied their vast amount of knowledge to the implementation of social policies, which is designed to improve the well-being of children and help them achieve their full potential. This is a global effort that several international organizations are part of. There are implications regarding social policies for specific parts of the development, other programs are designed for early intervention and aim to prevent early social and cognitive defects that come from neglect and poverty in early childhood. There are also programs to reduce bullying in schools and to reduce the impact on children who are being bullied. In addition, there are programs to detect autism, dyslexia and many other disorders. An example of a general program in the US is Head Start (a variant of which is Sure Start in England). This is a five-component program: pre-school education enrichment, screening of health, education about nutrition and hot meals, social services and education for parents. 

There are many areas in which research can contribute to the development of children. The main point is that research is not just a list of information: it has a practical purpose which is to better understand the development of children to ensure better attention to their needs and also to their familie's needs. 

What are the developmental functions?

From the data that developmental psychologists collect, analyze and interpret, it is possible to describe a number of developmental functions: the ways in which humans typically grow and change with age. Developmental functions are presented in graphs. Generally, the measurement of behavior is shown on the y-axis and the x-axis is used for age or time. The practical value is that they allow us to identify unusual patterns of development and to respond to them when necessary. The theoretical value is that the data can be used to evaluate hypotheses. Human development is very complex, and different aspects of development are changing in different ways. There are five most common functions, which will be presented below. 

Continous function (a) - increasing ability 

A common function is the continuous function (a) (increasing ability). This is perhaps the most common function in which we become better at a skill as we age. An example is intelligence: as children grow older, they generally become more intelligent. 

Continous function (b) - decreasing ability

Another common function is the continuous function (b) (decreasing ability). This means that in some things we get worse as we grow up. An example of this is the perception of speech in early childhood (see chapter 10). 

Discontinuous (step) function 

Another function that occurs is the discontinuous (step) function. In this function, development takes place in different phases, with each new phase being qualitatively different from the previous phases. It is easy to distinguish different phases in human life such as baby time, preschool time, childhood, adolescence, adulthood, etcetera. Stages of development are found in many areas of development. 

U-shaped functions

Two other types of developmental functions are inverted and upright U-shaped functions. This function is also very common in life. Inverted U-shaped functions are extremely common in development - we improve in the early years, stabilise or level off in adulthood and get worse as we get older. Inverted U-shaped functions can also be found in shorter periods. Upright U-shaped functions involve abilities which may be present early in life and disappear to re-emerge at a later age. For example the ability of newborn infants to turn their heads and eyes towars sounds. This auditory localisation response is present at birth, diminishes at around 6 weeks of age, and reappears again around 4 months of age. 

Comparing developmental functions

It may be useful to plot more than one developmental function in the same graph to be able to map possible causal relations. 

What can be concluded from this chapter?

Human development is extremely complex and multi-faceted. It is therefore not surprising that there are many ways to study development and many different types of developmental functions that emerge from the research as scientists try to understand how children grow and change.

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