Early ideas about love and relationships in the 20th century were heavily influenced by Freudian psychoanalytic theory. Other theories that emerged during this period included behaviourism and the social exchange theory.

The triarchic theory of love proposed by psychologist Robert Sternberg suggests that love can be broken down into three components: intimacy, passion, and commitment.

Three common challenges that romantic relationships face include communication issues, conflicts about expectations, and differences in values.

In the early 20th century, laws in several US states prohibited inter-racial marriages, with some states legally enforcing this through the notorious 'one-drop rule'.

The Reinforcement-Affect Theory of Attraction suggests that we tend to be drawn to people who provide us with positive reinforcement.

Three notable psychologists in the field of relationships research include John Gottman, Sue Johnson, and Robert Sternberg.

The similarity-attraction hypothesis suggests that people are more likely to be attracted to and form relationships with individuals who have similar characteristics to themselves.

Attachment styles describe the way we relate to others in close relationships. These styles can be divided into avoidant, anxious, or secure attachment styles that are closely linked to the way people experience and respond to intimacy.

In recent decades, marriage rates have declined as people are waiting longer to get married and choosing to cohabitate. Additionally, social and cultural changes around gender, sexuality and social norms have contributed to a decrease in the importance of marriage, particularly in Western societies.

Empathy is a key factor in building successful relationships. Being able to accurately understand and recognise other people's emotions, and respond appropriately, is a key component of developing healthy and fulfilling relationships.

Some common misconceptions about love include the idea that love is solely a feeling, that love is enough to maintain a successful relationship, or that true love should be effortless.

Common challenges faced by long distance relationships include trust issues, a lack of physical intimacy, and limited communication due to time zone differences.

The mere exposure effect states that people tend to become more attracted to stimuli that they are frequently exposed to.

The social exchange theory suggests that relationships are influenced by the costs and benefits associated with them. People are motivated to pursue relationships that offer the potential for positive outcomes.

Online dating poses challenges around authenticity, with users potentially creating inaccurate profiles or engaging in deceptive behaviours. Additionally, matching algorithms may not be effective predictors of attraction or compatibility.

The self-expansion model of intimate relationships proposes that seeking experiences that broaden and expand our self-concept is a key motivator in relationship formation and satisfaction.

The evolutionary perspective suggests that our attraction to others is influenced by the biological goal of maximising reproductive success. For example, men may be attracted to women who exhibit cues of fertility and women may be attracted to men who exhibit cues of social status.

Communication is a critical factor in building and maintaining healthy relationships, allowing partners to build trust, promote empathy, and negotiate conflicts and differences.

The attachment theory of love suggests that our attachment needs as infants continue to shape our patterns of relating to others throughout our lives.

Families with partners in the military face a range of challenges, including long periods of separation, frequent relocation, and the psychological impact of deployments and service-related injuries.