According to Sullivan, personality refers to the relatively enduring pattern of recurrent interpersonal situations which characterize a human life. This emphasizes the interpersonal situation. The interpersonal theory has two assumptions:

• The most important expressions of personality occur in interpersonal situations.
• Interpersonal is a fundamental concept and not necessarily observable (i.e. interpersonal refers to a sense of primacy).

Integrating tendencies bring people together in mutual pursuit of satisfaction (1), security (2) and self-esteem (3). Dynamisms refers to the dynamic between the self and the interacting partner. This gives rise to long-lasting concepts of the self and the other.

Each situation ranges from rewarding to very anxious (i.e. on an anxiety gradient). Interpersonal learning of self-concept and social behaviour is based on an anxiety gradient. The interpersonal situation underlies genesis (1), development (2), maintenance (3) and mutability (4) of personality through the continuous patterning and repatterning of interpersonal experience in relation to the needs. Individual variation in personality occurs through interaction between a person’s level of cognitive maturation and characteristics of the interpersonal situation encountered. Abnormal personality is expressed via disturbed interpersonal relations.

The interpersonal circumplex refers to a system of personality. It is not necessarily a classification system. It assumes that behaviour could be understood when related to a dynamic theory of personality. However, the circumplex is not an operationalization of the interpersonal theory. It describes enduring patterns of interpersonal behaviour and can demonstrate behavioural rigidity.

Interpersonal mechanisms refer to the process variables of personality (i.e. personality in action). It reflects the interaction process between group members. The focus is on behaviour and the variables can be measured on a scale of behavioural intensity. The basic dimensions of the circumplex are latent variables. The circumplex states that normal and abnormal personality lie on a continuum.

Interpersonal traits refer to enduring tendencies of personality. A trait refers to how a person behaves in certain situations. Abnormality refers to rigid reliance on a limited class of interpersonal behaviours regardless of situational influences or norms. They are often enacted at inappropriate levels of intensity. Normality refers to the flexible and adaptive deployment of behaviours covering the entire circumplex within moderate ranges of intensity.

Extremity refers to a person’s deviance from a normative position on a particular dimension on the circumplex. This is likely to be undesirable and rarely situationally appropriate or successful. Rigidity refers to a summary of one’s limited repertoires across various interpersonal situations. This is a characteristic of a person.

Intraindividual variability in interpersonal behaviours may be an important and stable individual difference variable. However, traditional measures of interpersonal functioning involve assessments at a single point in time. Flux refers to the variability of an individual’s mean score on a particular interpersonal dimension (e.g. aggression). Spin refers to the variability of the person’s angular position across time. Pulse refers to the variability in vector length.

The inventory of interpersonal problems measures abnormal personality traits. It measures whether people do something too much (e.g. arguing) or too little (e.g. standing up for oneself) and the amount of distress this causes. Vector elevation appears to be strongly related to general maladjustment.

Agency (i.e. vs. passivity) refers to the condition of being a differentiated individual. This is manifested in a person’s strivings for power and mastery which can enhance and protect one’s differentiation. Communion (i.e. vs. dissociation) refers to the condition of being part of a larger social or spiritual entity. This is manifested in strivings for intimacy (1), union (2) and solidarity (3) with the larger union. Agency and communion are superordinate to the circumplex.

Agency and communion mitigate each other. High levels of either are maladaptive because they preclude the expression of the other. A balance is optimal for psychological well-being;

1. Unmitigated agency
   This refers to the focus on the self and exclusion of others. This is associated with poor health behaviours (1), poor health outcomes (2) and interpersonal difficulties (3).
2. Unmitigated communion
   This refers to the focus on others and exclusion of the self. This is associated with negative views of the self (1), interpersonal difficulties (2) and interpersonal distress (3).

The interpersonal field refers to two personalities interacting. This eventually leads to the integration or disintegration of the interpersonal situation. A variety of transactional influences and reciprocal interpersonal patterns exist within this field. These patterns can resolve (1), negotiate (2) or disintegrate the interpersonal situation (3).

Social behaviour functions to fulfil the need to belong (1), the need to be yourself (2) and the need to be anxiety-free (3). The need to belong corresponds with communion. The need to be yourself corresponds with agency. Personality traits affect social behaviour (e.g. the tendency to trust in the goodwill of others).

Behaviour can be rated along agency and communion. These axes (i.e. agency and communion) can be explained by meta-concepts. This includes the needs (e.g. need to belong). It is possible that the need to be anxiety-free overrules the need to belong. This leads to distancing behaviour.

Integration in interpersonal situations refers to a process in which complementary needs are resolved or aggregated (1), reciprocal patterns of activity are developed or disintegrated (2) and a foresight or satisfaction of similar needs is facilitated (3). The interpersonal contingency process refers to a tendency for a given individual’s behaviour to be constrained or controlled in more or less predictable ways by the behaviour of the interaction partner. Interpersonal behaviours tend to invite restricted classes of responses from the other (e.g. friendly domination asks for friendly submission). If the desired response does not occur, negotiating or even disintegration of the interpersonal situation can occur.

Interpersonal complementarity refers to when there is a match between the field-regulatory goals of each person (i.e. agentic and communal goals). Reciprocity on dominance (1), correspondence on nurturance (e.g. friendliness) and equivalent behavioural intensity (3) define complementary behaviours. There can also be anticomplementary:

1. Acomplementary patterns (i.e. needs for agency and communion partially met)
   This refers to interpersonal patterns which meet one of the two rules for complementarity. This leads to negotiation to achieve complementarity.
2. Anticomplementary patterns (i.e. needs for agency and communion not met)
   This refers to interpersonal patterns which meet neither of the rules for complementarity. This leads to disintegration of the interpersonal situation.

Complementary reciprocal patterns promote relational stability. The perception of others’ behaviour and our enacted behaviour is affected by our self-concept. The interpersonal transactional cycle consists of four components:

• A person’s covert experience of the interaction partner.
• A person’s overt behaviour towards the person.
• A person’s covert experience in response to an action.
• A person’s overt behavioural response.

An interpersonal interaction is adaptive when interbehavioural contingencies mutually satisfy the agentic and communal needs of both participants. However, it becomes maladaptive when one person relies on a limited class of interpersonal behaviours. The other person can validate this behaviour (i.e. leading to repetition of this rigid behavioural cycle) or disintegrate the interaction.

Parataxic distortion refers to when the current interaction that takes place and the mental representation of the interaction does not correspond to one another (e.g. believing one is trying to harm you while this is not made clear in the interaction at all). The effects are chronic distortions of new interpersonal experiences in the covert phase of an ongoing transaction cycle and generation of rigid, extreme interpersonal behaviour in the overt phase of an ongoing transaction cycle. Abnormal interpersonal functioning is promoted when the covert interpersonal field is chronically encoded in distorted or biased ways.

One key aptitude distinguishing normal and abnormal personality is the capacity to enter into new proximal interpersonal situation without parataxic distortion. Impact messages refer to fundamental covert aspects of the interpersonal situation. It consists of four parts:

1. Feelings
   This refers to the elicited emotions.
2. Action tendencies
   This refers to the pull to do something (e.g. shout at the other person).
3. Perceived evoking messages
   This refers to the subjective interpretation of the other’s intentions (1), desires (2), affect state (3) or perception of interpersonal situation (4).
4. Fantasies
   This refers to the elaborations of the interaction beyond the current situation.