Chapter 8: Lifespan Development of Human Potential

Fetal and Infant Development

Nature/Nurture and The Development of Human Potential

Since the scientific revolution, we have acquired considerable information about the most mysterious and wonderful phenomenon on earth, life itself. The progression of knowledge regarding the mechanisms of heredity including genes, chromosomes, and DNA has recently culminated in the mapping of the human genome. We are on the cusp of discovering what is genetically unique about the human being and perhaps, what is unique about our biological potential. This knowledge, however, will not be sufficient to determine our potential as individuals or as a species. As described in Chapter 7, the pace of scientific discovery and technological advancement is accelerating with no limit in sight. Kurzweil has made the seemingly impossible prediction that in the not too distant future humans will become immortal! Unless things change dramatically, immortality will not occur for the Nukak. Tragically, extinction appears the more likely fate. “It is the best of times. It is the worst of times” (Dickens, 1859). Never has the human species been in a better position to consider the meaning of life. Never has our species possessed such power to create or destroy.

The following are the first three articles from the United Nations General Assembly Universal Declaration of Human Rights (December, 1948):

Article 1.

  • All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.

Article 2.

  • Everyone is entitled to all the rights and freedoms set forth in this Declaration, without distinction of any kind, such as race, color, sex, language, religion, political or other opinion, national or social origin, property, birth or other status. Furthermore, no distinction shall be made on the basis of the political, jurisdictional or international status of the country or territory to which a person belongs, whether it be independent, trust, non-self-governing or under any other limitation of sovereignty.

Article 3.

  • Everyone has the right to life, liberty and security of person.


Americans will recognize these sentiments as being consistent with Thomas Jefferson’s most famous words from the Declaration of Independence: “We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the Pursuit of Happiness.” The United Nations would apply these same ideals to the rest of the world. In order to achieve these noble objectives it is essential and strategic to focus our attention on children.







Figures 8.1 and 8.2   Amazonian rainforest children.



Brazil and Peru border on the Amazon. The photographs above, are of Ashaninka children in the Brazilan rainforest and Peruvian mainland children in school. I think you would agree, they might as well be on opposite sides of the world. The Ashaninka children are living similar to the ways their ancestors lived for thousands of years. Their environment is almost entirely natural. The Peruvian children’s environment was created by humans and includes laptop computers. These stark environmental differences enable us to appreciate Wechsler’s emphasis upon the adaptive and multi-faceted nature of human intelligence. The Ashaninka children must acquire the knowledge and skills accrued over thousands of years by previous generations of their tribe in order to survive. Peruvian children’s survival needs are met. They have the opportunity to explore the digitized accumulated knowledge of all the humans who have ever lived! A test to determine “intelligence” for one of these children would have to take their environmental conditions into consideration. Neither child could survive in the other’s world. The opportunities for the Ashaninka and Peruvian children to achieve their potential were determined by factors beyond their control at birth; where they were born and who their parents were. In this chapter, we will consider how nature and nurture interact to influence the course of human development from conception to adulthood.

Fetal Development

We are playing pretend. Congratulations! You have graduated, are romantically involved with a significant other, and expecting a child. The video below portrays the timeline for growth of a human fetus, be it in the rainforest or a city. During the first two months, the embryo consists of the layers of cells from which all organs and body parts will eventually develop. At three months, the fetus is about three inches long and weighs about an ounce. At four months, it is about five inches long and five ounces; the hardened skeleton is starting to form. At five months, the fetus reaches about ten inches in length and by six months, it weighs approximately one and a half pounds. At seven months, the fetus is about 15 inches in length and weighs about three pounds. The average birth statistics, after 39 weeks of pregnancy for children born in developed countries, are a length of 19 inches and weight of seven and a half pounds. Newborns vary considerably, even when taken to full term.


Watch the following video of fetal development:

Problems are least likely to develop during pregnancy for mothers between 16 and 35 years of age. Under modern conditions, the mother’s health and lifestyle can have a significant effect on the fetus; diseases can be transmitted through the placenta. Substance abuse (drugs or alcohol) or smoking can result in premature birth, lower birth weight, and greater risk of birth defects, miscarriages, or stillbirths. The mother’s diet can also affect the fetus: a lack of iron can produce anemia; a lack of calcium can affect the formation of teeth and bones; a lack of protein can reduce size and increase the likelihood of cognitive deficits.

Infant Development

Once again, congratulations! You are the proud parent of a healthy infant . The term “infant” is derived from the Latin word for “speechless.” It is generally applied to children up till three years of age although they typically start to speak earlier. Sometimes this period is sub-divided with separate “newborn” (between birth and one month) and “toddler” (between one and three years) stages. As we will see in the next chapter, some of your baby’s personality will be influenced by heredity. Since we are playing pretend, you get to choose whether your child is a girl or a boy and you can choose whether she/he is active and curious or quiet and relatively passive. Your new job is to insure achievement of the goals expressed in the UN Declaration of Human Rights. You want to make sure your bundle of joy eats, survives and does well in school.

Let’s start with eating. Breastfeeding is generally considered to be healthier for the child than bottle feeding (Gartner et al., 2005). As described in Chapter 5, infants are born with rooting and sucking reflexes, facilitating the nursing process for mother and child. After birth, the mother’s breasts swell as they fill with milk. Nursing reduces the swelling, providing a sense of relief along with other enjoyable feelings stemming from holding and nurturing one’s baby. For breast feeding to occur, the infant needs to grasp and hold onto its mother. In the same way that infants possess reflexes facilitating eating, they possess reflexes facilitating grabbing and holding (Schott & Rosser, 2003). If something is placed in an infant’s palm, a strong grasping reflex occurs. Should the infant sense a sudden loss of support, the Moro reflex occurs; the child first spreads its hands and then restores them to a holding position. Usually, between four and six months of age, it is possible to begin the weaning process, transitioning from liquid to solid foods. When the child’s baby teeth start to appear, usually around ten to twelve months of age, it is possible to introduce soft finger-sized foods.

This early nursing experience was considered crucial to establishing the important role of the mother. It was thought the mother became a conditioned reinforcer through classical conditioning by being paired with food. Research conducted with other species suggested that other factors besides feeding were important. Harry Harlow (1958), studying rhesus monkeys, was the first to demonstrate the important role of touch in infant development (see also Field, 2002). Harlow, using a controversial procedure, reared the monkeys in isolation from their mothers. He constructed two types of “surrogate mother” dolls. One had a wire cylinder for a body and the other was covered with soft terrycloth.

In order to measure the degree of preference for the dolls, Harlow used a procedure similar to the one to assess self-control in pigeons described in Chapter 1. You may recall that the pigeons had to choose between a small, immediate reward, and a larger, delayed reward. Preference was measured by the percentage of times the pigeon pecked the associated keys. Harlow measured the amount of time monkeys spent with the two types of “surrogate mothers.” He found that when hungry, the monkeys went to the doll with the bottle. At other times, the monkeys had a strong preference for the terrycloth doll. The terrycloth doll also served as a secure “home base” from which the monkey would explore novel items or return to when afraid. In the absence of the cloth doll, the monkey frequently cowered and sucked its thumb. In its presence, the monkey would usually cling to the cloth doll initially and then explore the new stimulus. If a fearful stimulus was presented (e.g., a teddy bear that made a loud sound), the monkey would often run and cling to its “mother” before working up the courage to once again explore the environment (Harlow, 1958).

You might be thinking Harlow’s research is interesting but questioning whether the findings relate to human children. This is an external validity issue and an empirical question. Mary Ainsworth developed the Strange Situation procedure to study attachment and exploratory behavior in children between 12 and 18 months of age (Ainsworth & Bell, 1970; Ainsworth, Blehar, Waters, & Wall 1978). The children were observed playing, with and without their mother present, while strangers walked in and out of the room according to the protocol described in the following video.


Watch the following video of Mary Ainsworth’s strange situation research with infants:

Separation anxiety was often observed when the caregiver (usually the mother) left the room. Stranger anxiety might be displayed toward the unknown adult. The infant’s exploratory behavior, as well as its behavior when being reunited with the caregiver, was also assessed. Ainsworth and Bell (1970) divided the children into Secure (70% of their sample), Insecure-Ambivalent (15%), and Insecure-Avoidant (15%) attachment styles based on their performance during the different episodes.

  • The Secure attachment style applied to children displaying low levels of anxiety and avoidance. They played with toys, explored the environment, and interacted with strangers when the caregiver was present. A secure infant might be upset and cry when the caregiver left the room but would appear happy when she returned. The child was still considered secure even if he/she refused to interact with the stranger when the caregiver was not present.
  • The Insecure-Ambivalent attachment style applied to children displaying inconsistent emotionality. They were resistant to exploration and strangers, even when the caretaker was present. These children became severely upset when the caretaker left the room but did not seem overly happy when she returned.
  • The Insecure-Avoidant attachment style applied to children who did not appear emotionally attached to the caregiver. They did not appear upset when she left the room or happy when she returned. These children appeared passive no matter who was present.

In longitudinal studies , individuals are studied over extended periods of time. Correlations between Strange Situation infant attachment styles and the quantity and quality of subsequent peer relationships have been found in major longitudinal studies (National Institute of Child Health and Human Development Study of Early Child Care 1991-1995, 1996-1999, 2000-2004, 2005-2008); Minnesota Study of Risk and Adaptation from Birth to Adulthood (Sroufe, Egeland, Carlson, & Collins, 2009)). Secure children have more friends, enjoy more positive relationships, and are more likely to become leaders than insecure children. Insecure-ambivalent children are frequently anxious and unsuccessful in seeking friends. Insecure-avoidant children may become aggressive, thereby discouraging friendships.


Watch the following video showing different attachment styles:

Consistent with Harlow’s research findings with monkeys, Ainsworth & Bell (1970) felt that different infant attachment styles were the result of different caregiver (usually maternal) characteristics:

  • Warm and consistently responsive caregiving (often involving holding and touching) was correlated with the secure attachment style.
  • Inconsistent and unemotional caregiving was associated with the insecure-ambivalent style.
  • Unresponsive caregivers, who frequently ignored the child, were associated with the insecure-avoidant style.

Parenting Styles

Can you remember how your parents treated and influenced you at different stages of your life? Do you wish to become a parent? If so, what type of parent do you wish to become? Contemporary parenting styles have been categorized on the dimensions of demandingness and responsiveness (Baumrind, 1968, 1971; Maccoby & Martin, 1983). Demanding parents specify clear rules of conduct and require their children to comply. Responsive parents are affectionate and sensitive to their children’s needs and feelings. he following video describes the four parenting styles resulting from different combinations of high and low demandingness and responsiveness.


Watch the following video showing different parenting styles:

We may consider the implications of the learning principles described in Chapters 5 and 6 for these different parenting styles. Negligent parents (low demandingness, low responsiveness) do not specify codes of conduct or respond to their children’s needs. If parents do not provide rules and/or consequences, the children will most likely be influenced by others (e.g., siblings, other adults, and eventually other children). From the perspective of the parents, This may result in the acquisition of undesirable behaviors.

Indulgent parents (low demandingness, high responsiveness) do not specify codes of conduct but are affectionate and responsive. They provide “unconditional positive regard” (Rogers, 1957), eliminating the contingency between desired behavior and consequence. We saw in Chapter 5, that the absence of a contingency between responding and consequences can result in learned helplessness. Non-contingent appetitive consequences (e.g., praise, gifts, etc.) can result in “spoiling” and a sense of entitlement. This could create problems for the children in other contexts (e.g., school, playgrounds) when others place demands and react differently to their behavior.

Authoritarian parents (high demandingness, low responsiveness) specify strict codes of conduct in a non-responsive manner. If the children ask for reasons, they may reply “because I say so!” In their parents’ absence, the children would seek other sources of authority.

Authoritative parents (high demandingness, high responsiveness) specify strict codes of conduct within a context of warmth and sensitivity to the children’s needs. They are likely to provide reasons for their codes of conduct, listen to their children’s perspective, and sometimes negotiate alternative codes. Authoritative parenting is most likely to result in secure attachment between parent and child.

Infant Skill Development

Now that you have thought about what type of parent you would like to become, you are most likely to concentrate on survival-related behaviors during the first years of your pretend child’s life. As we have seen, your child is equipped with nursing and grasping reflexes that facilitate an attached, dependent relationship with a caregiver. As a parent, you will begin walking the difficult tightrope balancing the need to nourish and protect your child with the need to foster independence. Early on, your child is immobile and her/his behavior seems sporadic and perhaps random. You might wonder if voluntary control learning (i.e., instrumental conditioning) is possible.

In a classic program of research, Carolyn Rovee-Collier (Rovee and Rovee, 1969) studied learning and memory in very young infants using a mobile suspended over their crib. A ribbon from the mobile could be attached to the infant’s leg. An active kicking motion would cause the colorful attachments to move. A reversal design (see Chapter 1) was employed in which the baseline frequency of kicking was assessed without the leg attached to the mobile, followed by a phase in which it was attached, and then a return to the detached baseline condition. The frequency of kicking in infants as young as eight weeks old, increased dramatically during the middle phase relative to the initial and subsequent baseline conditions. This is an early indication of the intrinsic motivation provided by controlling one’s environment.


Watch the following video of Rovee-Collier’s research:



Figure 8.1 “Ashaninka children” by Ministério da Cultura – Acre, AC is licensed under CC BY 2.0

Figure 8.2 “One Laptop per Child” by Ferreñafe is licensed under CC BY 2.0






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Psychology Copyright © by Jeffrey C. Levy is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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