Attachment style is the manner with which individuals relate to intimate partners. Levine and Heller have four categories of attachment styles: secure, anxious, avoidant, and anxious-avoidant. About 50% of people display characteristics of the secure attachment style, 20% exhibit anxious characteristics, and 25% exhibit avoidant characteristics. Only 3-5% of people fall under the anxious-avoidant category. Throughout the text, Levine and Heller emphasize The Importance of Understanding Attachment Styles and identifying one’s own. In addition, the authors encourage identifying a partner’s attachment style to determine compatibility. To aid readers with this process, Levine and Heller incorporate various assessments.

Present within the brain, the attachment system is a biological mechanism that builds attachment to attachment figures, which can include parents, children, and intimate partners. The attachment system also regulates attachment. The attachment system activates when separation occurs between attachment figures. As a result, certain emotions and behaviors emerge as a means of reestablishing connection. Levine and Heller describe how lack of awareness of one’s attachment system leads individuals, particularly those with an anxious attachment style, to struggle in intimate relationships. The categories of attachment style inform the kind of attachment system activated.