John Bowlby, the father of attachment theory, described several characteristics of attachment including the desire to be near those we are attached to, the feeling of being securely attached while separated, and the comfort experienced in turning to those with whom we are attached in times of distress.
Mary Ainsworth described three major styles of attachment observed in young children: secure, ambivalent, and avoidant.
Adults with a secure attachment style tend to have good self-esteem and to experience gratifying relationships with others in which they are more empathic and more able to comfortably self-disclose. They tend to have trusting, lasting relationships and are comfortable seeking out social support. Securely attached adults believe romantic love is enduring.
Adults with an ambivalent attachment style are more reluctant in becoming close with others. They worry that their partner does not reciprocate their feelings. Relationships may feel cold and distant. They become very distraught when relationships end. Ambivalently attached adults report falling in love often.
Adults with an avoidant attachment style may invest little emotion in their relationships with others. They share fewer thoughts and feelings with others. They may use excuses to avoid intimacy. They are less supportive of partners during stressful times. They tend to experience little distress when a relationship ends. Those with avoidant attachment styles describe love as rare and temporary.
Although the attachment style experienced during childhood can change in adulthood as a result of many intervening experiences, consideration with respect to the attachment experienced in the relationships with our parents while growing up may be helpful in better understanding the challenges we experience in our adult relationships.
For some individuals, it is helpful to learn that they can talk about themselves, their emotions, and their most important concerns in their relationships with others as adults without seeking safety in silence. For others, it is helpful to learn that they do not need to dodge real intimacy by being over-controlling in their relationships with others. For some individuals, it is helpful to learn that they need not avoid more intimate relationships by perseverating over superficial worries. And still for others, it is helpful to learn that they can assert themselves, express their own preferences, and maintain appropriate boundaries in relationships without having to overly defer to the wishes, needs, and demands of others.
In my post on Emotional Attacks, I share more information about experiences with insecure attachment in adulthood.