Law of Attraction
It all starts with mutual physical attraction. Scientists believe that dopamine, adrenaline and serotonin all come into play in this stage of love. During this stage, couples are mutually attracted to each other and keep entering into each other's thoughts. The chemicals in the brain can make the heart beat faster when they are together. Dopamine allows the human body to function with less sleep and increased energy. This also is the stage where sexual attraction is driven by testosterone and estrogen.
Time After Time
One of the signs of mutual love is the desire to spend time together. During this stage, couples take every opportunity they can to be in each other's presence. At this time, while they are getting to know each other, they also are unconsciously deciding if this is the right mate with which to reproduce. Humans detect good mating hormones, including pheromones, via the senses, especially the sense of smell and taste. On a conscious level, this is when people are finding out what interests they have in common.
Attached at the Hip
Becoming attached to each other is another sign of mutual love. Scientists believe that oxytocin is the hormone behind attachment. It is a bonding chemical that is released during sex. Mutual attachment is what makes a couple work things out after arguments and when a couple has sex often, it deepens the bond due to the release of oxytocin. Mutual attachment also is what keeps couples together long enough to raise children.
Happy Happy, Joy Joy
Mutual love is often demonstrated in the desire to make your partner happy. When a couple falls in love, they want each other to feel good and often show this in a variety of ways -- through respect, thoughtfulness and consideration. Putting your partner's needs before your own is one way to do this. Chemicals in the brain, such as dopamine and serotonin, play a part in this as well, but this behavior is typically a result of loving someone and wanting to make them happy.