18. Evolutionary and Ecological Aspects of Behavior


18.6. Human Behavior

We tend to think of human behavior as different from that of other animals, and it is. However, we are different only in the degree to which we demonstrate different kinds of behavior.

1. Instinctive behavior is rare in humans. We certainly have reflexes that cause us to respond appropriately without thinking. Touching a hot object and rapidly pulling your hand away is a good example. Newborns grasp objects and hang on tightly with both their hands and feet. This kind of grasping behavior in our primitive ancestors would have allowed the child to hang onto its mother’s hair as the mother and child traveled from place to place. But do we have more complicated instinctive behaviors? Newborns display several behaviors that can be considered instinctive. If you stroke the side of an infant’s face, the child will turn its head toward the side touched and begin sucking movements. This is not a simple reflex behavior but, rather, requires the coordination of several sets of muscles and involves the brain. It is hard to see how this is a learned behavior, because the child does the behavior without prior experience. Therefore, it is probably instinctive. This behavior may be associated with nursing, because carrying the baby on its back would place the child’s cheek against the mother’s breast. Other mammals, even those whose eyes do not open for several days following birth, are able to find nipples and begin nursing shortly after birth.

2. Habituation is a common human experience. We readily ignore sounds that are continuous, such as the sound of air conditioning equipment or the background music in shopping malls. Teachers recognize that it is important to change activities regularly to keep their students’ attention.

3. Association is extremely common in humans. We associate smells with certain kinds of food, sirens with emergency vehicles, and words with their meanings. Much of the learning we do is by association. We also use positive and negative reinforcement to change behavior. We seek to reward appropriate behavior and punish inappropriate behavior (figure 18.11). We can even experience positive and negative reinforcement without actually engaging in a behavior, because we can visualize its possible consequences. Adults routinely describe consequences for children, so that they will not experience harm: “If you don’t study for your biology exam, you’ll probably fail it.”




FIGURE 18.11. Negative Reinforcement

The reprimand this recruit is receiving is an example of negative reinforcement.


4. Exploratory learning is extremely common in humans. Children wander about and develop a mental picture of where things are in their environment. Exploration also involves behaviors such as picking things up, tasting things, and making sounds. Even adults explore new ideas and activities.

5. Imprinting in humans is more difficult to demonstrate, but there are instances in which imprinting may be taking place. Bonding between mothers and infants is thought to be an important step in the development of the mother-child relationship. Most mothers form very strong emotional attachments to their children; likewise, children are attached to their mothers, sometimes literally, as they seek to maintain physical contact with them. However, it is very difficult to show what is actually happening at this early time in the life of a child.

Language development in children may also be an example of imprinting. All children learn whatever languages are spoken where they grow up. If multiple languages are spoken, they learn them all and they learn them easily. However, adults have more difficulty learning new languages, and many find it impossible to “unlearn”) anguages they spoke previously, so they speak new languages with an accent. This appears to meet the definition of imprinting. Learning takes place at a specific time in life (critical period), the kind of learning is preprogrammed, and what is learned cannot be unlearned. Recent research using brain-imaging technology shows that those who learn a second language as adults use two different parts of the brain for language—one part for the native language or languages they learned as children and a different part for their second language.

6. Insight is what our species prides itself on. We are thinking animals. Thinking is a mental process that involves memory and an ability to reorganize information. A related aspect of our thinking nature is our concept of self. We can project ourselves into theoretical situations and measure our success by thinking without needing to experience a situation. For example, we can look at the width of a small stream and estimate our ability to jump across it without needing to do the task. We are mentally able to measure our personal abilities against potential tasks and decide if we should attempt them. In the process of thinking, we come up with new solutions to problems. We invent new objects, new languages, new culture, and new challenges to solve. However, how much of what we think is really completely new, and how much is imitation? As mentioned earlier, association is a major core of our behavior, but we also are able to use past experiences, stored in our large brains, to provide clues to solving new problems.



16. Give examples of instinct, habituation, association, and imprinting in humans.