Sleep timing is controlled by the circadian clock, sleep-wake homeostasis, and in humans, willed behavior. The circadian clock is an inner timekeeping, temperature-fluctuating, enzyme-controlling mechanism that works in tandem with adenosine, a neurotransmitter that inhibits many of the bodily processes associated with wakefulness.

Adenosine is created over the course of the day, with high levels of adenosine leading to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature.

The timing is affected by one’s chronotype, yet it is the circadian rhythm that determines the ideal timing of a correctly structured and restorative sleep episode. The need for sleep as a function of the amount of time elapsed since the last adequate sleep episode must be balanced against the circadian element for satisfactory sleep.

Along with corresponding messages from the circadian clock, this tells the body it needs to sleep. Sleep offset, or awakening, is primarily determined by circadian rhythm. A person who regularly awakens at an early hour will generally not be able to sleep much later than his or her normal waking time, even if moderately sleep-deprived.


Neural plasticity is the key to changes in intelligence. It occurs during short-term memory when a stimulus with a high frequency of activation causes improvement of a brain cell’s sensitivity to signals received from an associated cell. This change in neural connectivity allows information to be more easily processed, as the neural connection associated with that information becomes stronger.

It has been shown to play a large role in the development of the senses. For instance, blind patients have learned to “see” through tactile stimulation of their backs and tongues. The brain rewires the visual cortex to further process and interpret tactile stimulation in replacement of eyesight.

There are numerous behavioral factors that affect intellectual development. The key is neural plasticity, which is caused by experience-driven electrical activation of neurons. This experience-driven activation causes axons to sprout new branches and develop new presynaptic terminals. These new branches often lead to greater mental processing in different areas.

Those with a belief in fixed intelligence show less improvement on cognitive testing than people with a belief in neural plasticity, and a focus on performance goals and proving intelligence causes negative feedback and failure. Those who focus on flexible and expansive learning goals rebound well from occasional failure or feedback. By focusing on challenging tasks to expand intelligence instead of working to prove intelligence, neural plasticity allows greater intellectual capacity.


A supernormal stimulus is an exaggerated version of a stimulus to which there is an existing response tendency, or any stimulus that elicits a response more strongly than the stimulus from which it evolved.

The Dutch ethologist and ornithologist Niko Tinbergen constructed an artificial stimulus consisting of a red knitting needle with three white bands painted around it. This elicited a stronger food-begging response among chicks than an accurate three-dimensional model of the Herring Gull’s white head and yellow bill with a red spot. Tinbergen and his students studied other variations of this effect, experimenting with dummy plaster eggs of various sizes and markings, finding that most birds preferred eggs with more exaggerated markings than their own, more saturated versions of their color, and a larger size than their own.

Harvard psychologist Deirdre Barrett argues that supernormal stimulation governs the behavior of humans as powerfully as that of animals. In her 2010 book, Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose, she examines the impact of supernormal stimuli on the diversion of impulses for nurturing, sexuality, romance, territoriality, defense, and the entertainment industry’s hijacking of our social instincts. In her earlier book, Waistland, she explains junk food as an exaggerated stimulus to cravings for salt, sugar, and fats and television as an exaggeration of social cues of laughter, smiling faces and attention-grabbing action.

An episode of the PBS science show NOVA showed an Australian beetle species whose males were sexually attracted to large and orange females, the larger and more orange the better. This became a problem when the males started to attempt to mate with certain beer bottles that were just the right color. The males were more attracted to the bottles than actual females.


Emergence is the way complex systems and patterns arise out of a multiplicity of relatively simple interactions. It has been described as the creation of novel and coherent structures, patterns and properties during the process of self-organization in complex systems.

Emergent properties appear when a number of simple entities operate in an environment, forming more complex behaviors as a collective. Unintended consequences and side effects are closely related to emergent properties. Common characteristics include features not previously observed in other systems, and integrated processes that maintain themselves over a period of time.

The internet is a popular example of a decentralized system exhibiting emergent properties. There is no central organization rationing the number of links, yet the number of links pointing to each page follows a power law in which a few pages are linked to many times and most pages are seldom linked to.

Another important example of emergence in web-based systems is social bookmarking, also called collaborative tagging. In these systems, users assign tags to resources shared with other users, which gives rise to a type of information organization that emerges from this crowdsourcing process.


Empathy is the capacity to share the sadness or happiness of another sentient being. By the age of two, children normally begin to display the fundamental behaviors of empathy by having an emotional response that corresponds with another person.

It involves spontaneously and naturally tuning into the other person’s thoughts and feelings, whatever they might be. There are two major elements to empathy. The first is the cognitive component of understanding the others feelings and the ability to take their perspective. The second element is the affective component. This is an observer’s appropriate emotional response to another person’s emotional state.

Research in recent years has focused on possible brain processes underlying the experience of empathy. Functional magnetic resonance imaging has been employed to investigate the functional anatomy of empathy. These studies have shown that observing another person’s emotional state activates parts of the neuronal network involved in processing that same state in oneself.

Empathetic maturity is a cognitive structural theory that addresses how adults conceive or understand the personhood of patients. The theory, first applied to nurses and since applied to other professions, postulates three levels that have the properties of cognitive structures. The third and highest level is held to be a meta-ethical theory of the moral structure of care.


Instinct is the inherent inclination of a living organism toward a particular behavior. Instinctual actions have no learning curve. They are hard-wired and ready to use without learning. Some instinctual behaviors depend on maturational processes to appear.

Immediate instinct, also known as imprinting, causes geese to follow around the first moving object that they encounter, as it tends to be their mother. A favorable trait, such as an instinct, can improve survival rate of life forms possessing the instinct.

Many scientists consider that it is instinctual in children to put everything in their mouths, because this is how they tell their immune system about the environment and the surroundings, and what the immune system should adapt to.

A displacement activity is a behavior that is the result of two contradicting instincts in a particular situation. A human may scratch its head when it does not know which of two options to choose. Similarly, a bird may peck at grass when uncertain whether to attack or flee from an opponent.


The Asch experiments were a series of studies published in the 1950s that demonstrated the power of conformity in groups. Experiments led by Solomon Asch asked groups of students to participate in a “vision test.” In reality, all but one of the participants were confederates of the experimenter, and the study was really about how the remaining student would react to the others’ behavior.

The participants, the real subjects and the confederates, were all seated in a classroom. They were asked a variety of questions about lines printed on cards, such as how long is line A compared to the an everyday object, which line was longer than the other, which lines were the same length, etc. The group was told to announce their answers to each question out loud.

The confederates always provided their answers before the study participant, and always gave the same answer as each other. They answered a few questions correctly but eventually began providing incorrect responses.

Asch hypothesized that the majority of people would not conform to something obviously wrong. However, when surrounded by individuals all voicing an incorrect answer, participants provided incorrect responses on a high proportion of the questions. Seventy-five percent of the participants gave an incorrect answer to at least one question.

Variations of the basic paradigm tested how many confederates were necessary to induce conformity, examining the influence of just 1 confederate and as many as 15 confederates. Results indicate that 1 confederate has virtually no influence and 2 confederates have only a small influence. When 3 or more confederates are present, the tendency to conform is relatively stable.


Honesty refers to a facet of moral character and denotes positive, virtuous attributes such as integrity, truthfulness, and straightforwardness along with the absence of lying, cheating, or theft.

While there are a great many moral systems, honesty is considered moral and dishonesty is considered immoral. There are several exceptions, such as hedonism, which values honesty only insofar as it improves ones own sense of pleasure, and moral nihilism, which denies the existence of objective morality outright. Honesty may also be challenged in various social systems with ideological stakes in self-preservation. Many religious and national formations might be so characterized, along with many family structures and other small social collectives.

In these cases honesty is frequently encouraged publicly, but may be forbidden if those invested in preserving the system perceive it as a threat. Depending on the social system, these breaches might be characterized as heresy, treason, or impoliteness. Even in moral systems which approve in general of honesty over dishonesty, some people think there are situations in which dishonesty may be preferable.

Others would not define preferable behaviors as dishonest by reasoning that they are not intended to deceive others for personal gain, but the intent is noble in character, for example sparing people of opinions that will upset them. Rather than dishonesty, the behavior is often viewed as self sacrifice or giving up one’s voice for the happiness of others. In many circumstances, withholding one’s opinions can legitimately be viewed as cowardly, dishonest and a betrayal to those who will be hurt. For this reason, many people insist that an objective approach to the truth is a necessary component of honesty as opposed to an ideological or idealistic approach.


Social capital is a sociological concept used to refer to connections within and between social networks. Though there are a variety of related definitions, they tend to share the core idea that social networks have value. Just as a screwdriver (physical capital) or a college education (human capital) can increase productivity (both individual and collective), so do social contacts affect the productivity of individuals and groups.

Early attempts to define social capital focused on the degree to which social capital as a resource should be used for public good or for the benefit of individuals. It has been suggested that social capital can facilitate co-operation and mutually supportive relations in communities and would therefore be a valuable means of combating many of the social disorders inherent in modern societies.

Child development is powerfully shaped by social capital and the continued presence of social capital has been linked to various positive outcomes, particularly in education. In areas where there is a high social capital, there is also a high education performance. When there is more parental participation in a child’s community and education, teachers have reported lower levels of student misbehavior.

It has been argued that one of the reasons social capital is so difficult to measure is that it is neither an individual nor a group level phenomenon, but one that emerges across discreet levels as individuals participate in groups. They argue that the metaphor of social capital may be misleading because unlike financial capital, which is a resource held by an individual, the benefits of forms of social organization are result of the participation of individuals in advantageously organized groups.


Gratitude, thankfulness, or appreciation is a positive emotion or attitude in acknowledgment of a benefit that one has received or will receive. The systematic study of gratitude within psychology only began around the year 2000, possibly because psychology has traditionally been focused more on understanding distress rather than understanding positive emotions. However, with the advent of the positive psychology movement, gratitude has become a mainstream focus of psychological research. The study of gratitude within psychology has focused on the understanding of the short term experience of the emotion, individual differences in how frequently people feel gratitude, and the relationship between these two aspects.

Gratitude is not the same as indebtedness. While both emotions occur following help, indebtedness occurs when a person perceives that they are under an obligation to make some repayment of compensation for the aid. The emotions lead to different actions; indebtedness motivates the recipient of the aid to avoid the person who has helped them, whereas gratitude motivates the recipient to seek out their benefactor and to improve their relationship with them.

Gratitude may also serve to reinforce future prosocial behavior in benefactors. For example, one experiment found that customers of a jewelry store who were called and thanked showed a subsequent 70% increase in purchases. In comparison, customers who were thanked and told about a sale showed only a 30% increase in purchases, and customers who were not called at all did not show any increase. In another study, regular patrons of a restaurant gave bigger tips when servers wrote “Thank you” on their checks.

A large body of recent work has suggested that people who are more grateful have higher levels of well-being. Grateful people are happier, less depressed, less stressed, and more satisfied with their lives and social relationships. Grateful people also have higher levels of control of their environments, personal growth, purpose in life, and self acceptance. Grateful people also have less negative coping strategies, being less likely to try to avoid a problem, or deny there is a problem, blame themselves, or cope through substance use. Grateful people sleep better, and this seems to be because they think less negative and more positive thoughts just before going to sleep.