from one hemisphere to the other.
Despite removal or disconnection of several brain regions, children usually show remarkable recovery from the surgery. Children often experience weakness or mild paralysis on the opposite side of the body. Furthermore, if the left hemisphere is removed, most children experience problems with language. However, children usually recover much of this lost functioning within 6 to 12 months after surgery, as the remaining hemisphere gradually assumes many of these lost functions. In fact, most children who undergo this surgery are able to return to school 6 to 8 weeks later (van Schooneveld, Braun, van Rijen, van Nieuwenhuizen, & Jennekens-Schinkel, 2016).
Positive environmental experiences can also lead to the formation of new neural connections. Long ago, the neuropsychologist Donald Hebb (1949) proposed that the simultaneous activation of neurons can cause the neurons to form new connections. Hebb suggested “neurons that fire together, wire together.” Recently, neuroscientists have been able to show synaptogenesis, that is, the formation of new neural connections due to experience. For example, rats reared in enriched living environments (e.g., given extra space and access to toys and mazes) show differences in brain structure and functioning compared to rats reared in typical cages. Humans who receive extensive training in Braille show growth in brain regions responsible for processing the sense of touch. Even skilled musicians show a reorganization of brain regions responsible for controlling the finger positions of their instruments (Cicchetti, 2019).
Review
The brain consists of 100 billion neurons that form trillions of synaptic connections. Neurons relay information within themselves electrically; they communicate between one another using chemical messengers called neurotransmitters.
Brain development is characterized by rapid growth followed by periods of neuronal pruning. Development begins in evolutionarily older brain regions (e.g., brainstem, basal ganglia, limbic system) and ends in regions responsible for higher-order functions (e.g., the cerebral cortex).
Development can be gene driven, experience expectant, or experience dependent. Environmental experiences can lead to synaptogenesis and the reorganization of neuronal connections (i.e., plasticity).
2.3 Psychological Influences on Development
How Is Learning Theory Important to Understanding Childhood Disorders?
Psychologists often use learning theory to explain and predict children’s overt actions. From the perspective of learning theory, children’s behavior is largely determined by environmental contingencies. Learning occurs in three ways: (1) through classical conditioning, (2) through operant conditioning, and (3) through imitation or modeling.
Classical Conditioning
In classical conditioning, learning occurs when the child associates two stimuli paired together in time. One stimulus is initially called the neutral stimulus (NS) because it does not elicit a response. The other stimulus is initially called an unconditioned stimulus (UCS) because it elicits an unlearned or unconditioned response (UCR). The child may come to associate the NS with the UCS if the two stimuli are presented together in time.
Pavlov demonstrated that dogs would associate the sound of a metronome (NS) with the presentation of meat powder (UCS) if the two stimuli were presented contiguously. After repeated presentations, the metronome alone elicited salivation. After conditioning, the previously neutral stimulus (e.g., metronome) is referred to as the conditioned stimulus (CS), whereas the resulting response (e.g., salivation) is referred to as the conditioned response (CR).
Classical conditioning can be used to explain the emergence of certain childhood disorders. For example, a boy who is bitten by a dog might associate the sight of a dog (NS) with the experience of being bitten (UCS). The dog bite, in turn, naturally causes a fear response (UCR). Later, the presence of any dog (CS) may elicit a similar fear response (CR). The boy might develop a phobia for dogs.
Consider another example. A girl is taking notes in her high school math class when she suddenly experiences a panic attack. The attack is so severe that she immediately leaves class and runs to the bathroom for privacy and safety. The girl associates her classroom (NS) with the panic attack (UCS), which naturally causes intense negative emotions (UCR). Later, any thought of reentering her classroom (CS) might elicit feelings of apprehension or anxiety (CR). She might develop a fear of going to school.
One way of decreasing behaviors acquired through classical conditioning is to repeatedly expose the CS until the severity of the CR decreases. When the CS no longer elicits the CR, we say that extinction has occurred.
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Exposure therapy is a primary treatment for most anxiety disorders. In a process called graded exposure, extinction occurs gradually. For example, a therapist might recommend that a boy with a fear of dogs gradually spend more time with dogs, in order to extinguish this fear. Initially, the boy might simply look at pictures of dogs, then remain in a room with a dog on a leash, and finally pet a dog. After the boy is repeatedly exposed to the dog, the dog’s presence no longer elicits an intense fear response (Image 2.7).
In a process called flooding, extinction occurs rapidly—usually within one session. For example, a girl with a fear of school might enter her math classroom with her therapist and remain there until her panic subsides. Although flooding is a more rapid treatment than graded exposure, it is less frequently used with children because it causes greater distress.
Operant Conditioning
Whereas classical conditioning occurs when children associate two stimuli together in time, operant conditioning occurs when children associate an action with a consequence in the environment. Operant conditioning is based on the notion that the consequences of our actions determine the likelihood that the actions will be repeated.
If the consequences of our actions increase the likelihood that we will repeat the behavior in the future, these consequences have reinforced our behavior. Reinforcement can be positive or negative. Positive reinforcement occurs when an individual is presented with a stimulus that increases the likelihood of behavior. For example, a father might give his daughter ice cream after she eats her vegetables at dinner. If the presentation of ice cream following the meal increases the likelihood that the girl eats her vegetables in the future, we say that the ice cream positively reinforced the child’s eating.
Many people mistakenly believe that the adjective “positive” in the term positive reinforcement refers to the pleasantness of the reinforcer. In fact, the term positive simply refers to the fact that the stimulus is presented to the individual. Some presumably pleasant stimuli are not positively reinforcing to all children. For example, providing a 2-year-old with one piece of candy for using the toilet may increase the likelihood that he will use the toilet in the future. However, providing one piece of candy to a 14-year-old for completing his math homework will likely not increase the likelihood that he will complete his math homework in the future.
Additionally, some presumably unpleasant stimuli can be positively reinforcing. For example, a teacher may reprimand her student for disrupting class. If the teacher’s reprimand results in an increase in the student’s disruptive behavior, the teacher’s behavior is positively reinforcing, no matter how aversive it appears.
Negative reinforcement occurs when the withdrawal or avoidance of a stimulus increases the likelihood of behavior. For example, a father might allow his daughter to leave the dinner table only after she finishes her vegetables. If escaping the dinner table by eating vegetables increases the likelihood that the girl eats her vegetables in the future, we say that the father’s actions negatively reinforced the child’s eating.
Negative reinforcement often underlies childhood