Attachment approaches, initially developed by Bowlby (1969, 1973, 1980, 1988) provide a model of how we form links with other people. In these works, Bowlby argues that from birth, we have an innate drive to form a psychological bond with others (in the case of neonates and infants, we usually seek attachment with adults, as the latter can protect the former). The quality of our early attachments (for instance, how sensitive the caregiver is to needs, and how responsive they are to needs once recognized) influences the development of an internal working model of how relationships function – for instance, how/if others can be trusted and relied upon. This model is then carried into adult life, affecting how we relate to others.

More recent perspectives based on this approach have been advanced by Fraley et al. (2000) and Rholes & Simpson, (2004). These perspectives argue that attachment can be broadly separated into two dimensions: attachment anxiety and attachment avoidance. Rholes and Simpson (2004) argued that attachment anxiety is characterized by a high need for attention, but coupled by a distrust that the caregiver has the will or ability to deliver it. In contrast, avoidance anxiety is a difficulty with intimacy and over-reliance on self-sufficiency and independence. These dimensions can be combined to create a taxonomy of four categories of attachment: secure (low on both dimensions), preoccupied (high anxiety, low avoidance), dismissive (low anxiety, high avoidance), and fearful (high on both dimensions). These influence how we seek out/avoid closeness in relationships, rely on others, allow ourselves to have others rely on us, and judge ourselves in contrast (or not) to others’ perceived evaluations. Once established, attachment models are traditionally considered to be relatively fixed for life, although secure attachment can be ‘earnt’ – which can involve an ongoing process of consciously challenging the established internal working model (see e.g. Saunders et al., 2011).

Child attachment patterns have been shown to longitudinally predict the number and quality of later adult relationships ( Lyons-Ruth et al., 2013). Attachment styles have also been linked to mental well-being (e.g. Raque-Bogdan et al., 2011), the ability to function in therapeutic groups ( Marshall et al., 2018) and offspring attachment styles ( Harper, 2005; Moullin et al., 2018). Parental attachment also appears to influence mental health ( Galbally et al., 2020). While the outcomes and emotional/behavioural markers associated with each style are well established, the relationship between attachment and another major process in relation to object relation maturity is relatively unexplored.

Object relation maturity perspectives focus on the complexity of representations of and relationships between the self and other social objects (traditionally defined as people) ( Ogden, 1983). Such approaches argue that as we psychosocially mature we develop more complicated representations of these objects, which allow both positive and negative elements and evaluations of others to be held simultaneously. This allows more nuanced relationships (including navigation of need and reliance on others, being available to others, etc.) to be managed successfully ( Klein, 1952; Ogden, 1986). While object relation maturity and attachment overlap conceptually (as models of how we relate and some features such as self/other reliance, etc.) and arguably in practice therapeutically, they are also generally considered in isolation in terms of theory and practice (likely for historical reasons in the development of the field).

The precursor of object relation maturity is characterized by psychological splitting, which is the focus of this study. Splitting involves the separation of objects into distinct elements (part-objects), which are individually all good or bad, and/or the reduction of complex objects into simple, ‘good’ or ‘bad’ ones. We may feel ambivalent towards dichotomous evaluations of good or bad. For instance, a partner may in turn be completely idolized and vilified. Splitting can include the splitting of the self, with aspects of the self that cannot be self-managed or accepted projected onto others or repressed. Psychosocially, we begin operating solely in this manner by splitting all objects, including the self (in Kleinen terms, operating from a paranoid-schizoid position; Klein, (1952)). Under normal circumstances, we can manage a more complex set of representations (more mature object relations, Klein’s depressive position) at around 6 months of age. While both positions are available across the lifespan, failure to move beyond reliance on splitting in early childhood is seen as a causative factor in borderline personality disorders and other mental health challenges ( Huprich et al., 2017), as well as impacting day-to-day relationships.

In both clinical and non-clinical populations, splitting is argued to be functional as a defense mechanism, as it removes potentially distressing ambivalence around the nature of significant others and our relationships with them (which, many argue, are inherently ambiguous; Gerson, 1984; Siegel & Spellman, 2002). However, when splits are within the self and/or involve projecting or introjecting elements of the self or others, they also provide cognitive distortions that may impact functional relationships with others. In addition to being seen as essential to understanding the pathology of many mental health conditions from the object relations perspective, splitting is observed among nonclinical populations, especially when individuals are exposed to stress ( Lopez et al., 1997).

Alongside splitting operating at an individual level, within close relationships, dyadic splitting is characterized by co-dependence and dramatic shifts between threats to destroy and urgent need to reconcile with the relationship partner, both driven by split object relationships ( Solomon, 1985). Siegel (2006) argues that this dyadic splitting is a constellation of behaviors and defenses such as splitting, denial, and projective identification (inducing another person to experience emotions that the individual cannot tolerate experiencing themselves). Functionally, couples experiencing dyadic splitting may learn to avoid potential conflicts – this eliminates the possibility of growth and leads to exaggerated and destructive responses when the ‘all bad’ version of the self, the other, or the relationship emerges. As both sides of the dyad experience this separately, finding a common shared meaning for events is difficult until they achieve more mature object relations. In contrast to attachment, which has an established evidence base, object relations maturity (and the phenomenon of splitting specifically) has relatively limited empirical evidence (detailed below). This lacuna is both in terms of the genesis and developmental trajectory of object relation maturity and the more observable outcomes (i.e., the act of splitting, projection, etc.). This study begins to expand on the latter aspect (outcomes).

The attachment and object relations maturity approaches both posit that affective and cognitive systems associated with relationships with others guide the function and success of our psychosocial lives. One open question is the extent to which these processes overlap and/or are distinct systems, and how they are conceptually related. The current study explores the relationship between the two major dimensions of attachment (anxiety and avoidance) and the defense mechanism of splitting (an indicator of object relation maturity experienced both at an intra-aethicnd interpersonal level, i.e., splitting and dyadic splitting).

While both broadly object-relation approaches (in that they focus on the relationship between psychosocial objects), attachment style and object-relation maturity perspectives differ in emphasis. Key differences in the approaches focus on the etiology of developmental goals, with attachment theories highlighting the external world (i.e., parental responsiveness and the importance of early social interactions with primary caregivers) vs. an (arguably inaccurate) perception that object relation maturity focuses overly on the child’s internal phantasy world (see Ogden, 1986 for a discussion as to whether this perception of an exclusive focus on the internal world of the child is an oversimplification or not).

Previous empirical studies have linked object relation maturity (in general) with attachment style. Priel and Besser (2001) demonstrated that securely attached women (in their third trimester of pregnancy) have more complex, integrated object relations than those with less secure styles. Structural equation modelling also suggested that the constructs were related but distinct ( Westen, 1991). Similarly, Levy et al. (1998) showed that more securely attached individuals demonstrated more complex integration in their object relations (although fearful attached participants also demonstrated high levels of object relation complexity). Similarly, Calabrese et al. (2005) showed that those who experienced others as providing a secure emotional base and connection also had more complex representations of both self and others.

Specific to splitting, Lopez et al. (1997) showed that both securely attached and dismissive participants had lower splitting tendencies, linking them to lower levels of parental care. Mikulincer and Orbach (1995) highlighted an increase in object relation-related defense mechanisms surrounding perception among individuals with insecure attachment ( Siegel & Spellman, 2002). Looking at intimate relationships, Siegel (2006) observed that links between levels of within-relational problems such as blame, devaluing, conflict, and contempt were all linked to higher levels of dyadic splitting. The same pattern of results was observed in domestic abuse (both in terms of perpetrators and victims; see Siegel and Spellman (2002).

Thus, there is a small but growing evidence base that links attachment security to (i) object relations maturity and (ii) specifically to the use of splitting as a defense. Both impact the quality (and indeed safety) of individual relationships with others in both broad and intimate relationship contexts. However, their relationship remains unknown.

One limitation of the above works is that they categorized participants into attachment types (losing sample variance in the process), relied on narrative-based measures of object relation maturity, and/or focused on relatively narrow populations. By contrast, attachment can be seen as a two-dimensional system based on attachment anxiety and avoidance ( Fraley et al., 2000), and object relation maturity can be measured quantitatively (reducing potential subjectivity). In addition, while some existing studies look at the covariance between attachment and object relation maturity, they do not consistently look at mental wellbeing/distress as an outcome. Given the importance of splitting and attachment issues as features in a variety of mental health conditions, it is important to understand how these are linked (or not). Finally, the above studies have not looked at the relative impact of attachment and splitting on outcomes; rather, they have assumed (or implied) a causation between attachment style and subsequent object relation maturity.

The current study aimed to build upon extant research while also exploring conceptual models that describe relevant relationships. Specifically, the study explored a model in which the effects of splitting are mediated through attachment (i.e., splitting is related to attachment avoidance and/or anxiety, which in turn is linked to mental health) and an alternative in which attachment effects are mediated through splitting. This approach allows an exploration of which processes predict unique variance in outcomes and provides possible models of the interrelationship between these constructs. Given the relative paucity of work in this area, exploratory analyses were undertaken with no a priori hypotheses beyond the expectation that higher splitting, attachment anxiety, and attachment avoidance would be linked with higher mental distress.

All scales can be seen on the OSF site for this project (see Extended Data, below for details).

Splitting. The Gerson (1984) splitting scale was used to measure splitting. This included ten items such as ‘I hate to hear someone close to me being criticized and When I am angry, everyone around me seems rotten.’, ‘There are times my partner seems as strong as iron, and at other times as helpless as a baby,’ which capture the tendency to split objects into good and bad. The anchors were 1 (Strongly Disagree) and 7 (Strongly Agree). The scale author reported good internal reliability (Cronbach’s α = 0.70, Gerson, 1984), and later authors reported similar (Cronbach’s α 0.68, Lopez et al., 1997). In the current sample, reliability was moderate (Cronbach’s α = .66) with 10 items. Internal reliability analysis revealed that dropping one item (‘It’s hard for me to get angry with people I like”) increased reliability to 0.74, and this nine-item model was adopted for the current study. Higher scores indicated increased splitting. This scale is not a proprietary research instrument.

Dyadic splitting. For participants who indicated that they were in an intimate relationship (n = 37), the Siegel and Spellman dyadic splitting scale was deployed ( Siegel & Spellman, 2002). This comprised items anchored at 1 (Strongly Disagree) and 4 (Strongly Agree). Sample items include; “We have a roller-coaster relationship. I never know when things are going to fall apart quickly.” and “I never know whether my partner is going to think I am the best or the worst person in the world.” . Reliability was good (Cronbach’s α = 0.83). Higher scores indicated increased splitting. This scale is not a proprietary research instrument.

Attachment style. The ECR-R scale was used to measure anxiety and avoidant attachment ( Fraley et al., 2000). This is a 35-item scale with items anchored at 1 (Strongly Disagree) and 7 (Strongly Agree). For anxious attachment, sample items included I do ‘not often worry about being abandoned’ and ‘My romantic partner makes me doubt myself.’. For avoidance, sample items included ‘I am nervous when partners get too close to me.’ and ‘I find it easy to depend on romantic partners.’ For all items, scores were coded such that higher scores were related to more anxiety/avoidance. The anxious attachment reliability was good (Cronbach’s α = .93). Avoidant attachment reliability was also good (Cronbach α = .94). This scale is not a proprietary research instrument.

Mental distress. Mental distress was measured using the combined General Anxiety Disorder questionnaire (GAD7, Spitzer et al., 2006) and the Patient Health Questionnaire (PHQ-8, Kroenke et al., 2009). These scales measure frequency of symptomology experienced problematically over the last 2 weeks, including items such as ‘Feeling nervous, anxious, or on edge,’ ‘Feeling down, depressed, or hopeless,’ ‘Being so restless that it’s hard to sit still’ and ‘Poor appetite or overeating.’ In line with Kroenke et al. (2016), these scales were collapsed to create a single distress score (Cronbach α = .91). These scales are not proprietary research instruments.

Procedure. Participants completed the online measures. First, a participant information sheet was presented. Following this, all participants provided written informed consent via the questionnaire platform (see Ethics, below) participants completed the measures in the order presented above. Finally, they were thanked and debriefed. Please see the Extended Data (below) for details on how to access full versions of these documents.

Ethics: This study received ethical oversight and approval from London South Bank University (reference number ETH2223-0024, granted 14th October 2022). It was conducted in accordance with APA’s ethical standards. All the participants provided written informed consent and were debriefed at the end of the study.

To test the proposed direct and indirect relationships, a mediation model was developed using the Hayes PROCESS macro (v4.2, Hayes, 2017). In the first model (n = 69 due to incomplete cases; see Figure 1 for model), splitting was included as the predictor and mental distress as the criterion variable. The 95% confidence intervals were reported from 5000 bootstrap samples ¹ . The overall model was significant ( R ² = .23, F(3,65) = 6.76, p <.001. Splitting scores were related to anxious attachment ( a ₁ = 0.61, CIs = 0.35, 0.87) and avoidant attachment ( a ₂ = .40, CIs = 0.14, 0.67). In the full model, splitting was also related to mental distress ( c’ = 3.82, CIs = 1.27, 6.36). Anxious attachment was not related to mental distress ( b ₁ = 1.44, CIs = -0.69, 3.57) or avoidant attachment ( b ₂ = -0.12, CIs = 2.15, -1.90). No significant indirect effect of splitting on mental distress via anxious ( a ₁ b ₁ = 0.88, CIs = -0.92, 2.41) or avoidant ( a ₂ b ₂ = -.05, CIs = -1.08, 0.74) attachment was observed. Achieved power analysis, calculated using the med function from the pwr2pll R library, revealed the sample was sufficient to detect mediation with a power of 0.80 when α = 0.05.

Although the sample for dyadic splitting was too small to draw conclusions from (n = 37), confirmatory analysis using dyadic splitting as the predictor variable showed the same pattern of results and significance levels.

In summary, this analysis suggests that the variance in mental distress is related to splitting, but we did not observe mediation via attachment. Moreover, it also suggests that the variance across both splitting and attachment is considered simultaneously, and attachment dimensions do not predict unique variance.

Two alternative mediations with each dimension of attachment as predictors of mental distress, mediation by splitting, revealed no significant relationship between the attachment dimension and distress (as expected from the previous analysis), direct links between splitting and mental distress (again, as one would expect), and no mediation.