Changes

Biological models of sex tend to view love as a [[mammal]]ian drive, much like [[hunger]] or [[thirst]].(A General Theory of Love ,ISBN 0375709223).  "Experts" in the topic of love, divide the [[experience]] of love into three partly overlapping stages: lust, attraction, and attachment. Lust exposes people to others; romantic attraction encourages people to [[focus]] their energy on mating; and attachment involves tolerating the spouse (or indeed the child) long enough to rear a child into infancy.  

Biological models of sex tend to view love as a [[mammal]]ian drive, much like [[hunger]] or [[thirst]].(A General Theory of Love ,ISBN 0375709223).  "Experts" in the topic of love, divide the [[experience]] of love into three partly overlapping stages: lust, attraction, and attachment. Lust exposes people to others; romantic attraction encourages people to [[focus]] their energy on mating; and attachment involves tolerating the spouse (or indeed the child) long enough to rear a child into infancy.  

[[Lust]] is the initial passionate sexual desire that promotes [[mating]], and involves the increased release of chemicals such as [[testosterone]] and [[estrogen]]. These effects rarely last more than a few weeks or months. Attraction is the more individualized and romantic desire for a specific candidate for mating, which develops out of lust as commitment to an [[individual]] mate forms. Recent studies in [[neuroscience]] have indicated that as people fall in love, the brain consistently releases a certain set of chemicals, including [[pheromones]], [[dopamine]], [[norepinephrine]], and [[serotonin]], which act in a manner similar to [[amphetamine]]s, stimulating the brain's [[pleasure center]] and leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement. Research has indicated that this stage generally lasts from one and a half to three years.

Lust is the initial passionate sexual desire that promotes [[mating]], and involves the increased release of chemicals such as [[testosterone]] and [[estrogen]]. These effects rarely last more than a few weeks or months. Attraction is the more individualized and romantic desire for a specific candidate for mating, which develops out of lust as commitment to an [[individual]] mate forms. Recent studies in [[neuroscience]] have indicated that as people fall in love, the brain consistently releases a certain set of chemicals, including [[pheromones]], [[dopamine]], [[norepinephrine]], and [[serotonin]], which act in a manner similar to [[amphetamine]]s, stimulating the brain's [[pleasure center]] and leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement. Research has indicated that this stage generally lasts from one and a half to three years.

Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as [[marriage]] and children, or on mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals [[oxytocin]] and [[vasopressin]] to a greater degree than short-term relationships have.

Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as [[marriage]] and children, or on mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals [[oxytocin]] and [[vasopressin]] to a greater degree than short-term relationships have.

The protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year.  “Raised plasma nerve growth factor levels associated with early-stage romantic love.” [http://www.biopsychiatry.com/lovengf.htm Abstract].  

The protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year.  “Raised plasma nerve growth factor levels associated with early-stage romantic love.” [http://www.biopsychiatry.com/lovengf.htm Abstract].

===Psychological basis===

===Psychological basis===