Loneliness is often caused by a combination of several of the other three common human weaknesses, for instance, fear and laziness: fear of rejection while trying to find new friends and laziness in making the attempt.
Fear is a very common weakness and is related to our needs. Abraham Maslow[3] classified these needs as follows:
1. Physical safety.
2. Food and shelter.
3. Love or belonging—the need to love and be loved.
4. Career—the need to be successful at something.
5. Self actualization—the need some people feel to become who God wants them to be.
People must meet their immediate, basic needs for physical safety before they can meet their wishful needs for love or fulfilling a career. While we strive to behave as thinking people, with well thought out plans, sometimes we act purely as animals by instinct alone. If we are suddenly frightened by a snarling dog, we react by running or fighting, instinctively, without conscious thought. Paul MacLean describes what happens in our brains as a stepping down the evolutionary ladder and using those parts of our "Triune" brain that operates on instinct rather than thought. [4]
MacLean divides the Triune brain [5] into three parts that developed over the evolutionary eons. The oldest, which he calls the reptilian brain, controls aggression and passionate impulsiveness. The middle region, the limbic system, controls docile, loving emotions. The outer region, the neo-cortex controls thoughtful planning with an awareness of consequences and cause-effect relationships. This phenomenon is important because fear alone can inhibit successful higher level thinking by keeping the brain at the lowest (reptilian) level preparing to meet the threat. The educator Lev Vygotsky stressed the importance of creating and maintaining a risk-free environment that encourages higher level (neo-cortex) thought. [6] The growing recognition of the Triune Brain might very well have influenced world politics in the replacement of the policy of "mutually assured destruction" with a "kinder and gentler" statesmanship.
Maslow's need and MacLean's brain are both related to animal-like behavioral weaknesses when we react impulsively rather than with thought and planning, and we are more likely to act impulsively when our physical safety or food and shelter needs are threatened.