To date, only one other study7 has addressed objectum sexuality (OS) and our research is the first to take an empirical behavioural approach in studying this form of sexual orientation. We recruited a group of individuals who self-identify as OS and a group of non-OS controls. Our study was motivated by the hypothesis that autism and synaesthesia (i.e., object-personification synaesthesia) might play a role in OS, at least for some OS individuals.

We found a number of significant relationships between OS and synaesthesia. Firstly, we found that the romantic affections of OS individuals towards objects do appear to be driven, at least in part, by object-personification synaesthesia. This was revealed by the fact that OS individuals do tend to sense personality traits in their object-partners, and that these show the synaesthetic hallmark of consistency-over-time (i.e. the OS group were significantly more consistent compared to controls when assigning personalities to inanimate objects). We propose that synaesthetic personalities and genders might increase the anthropomorphic qualities of inanimate objects which could facilitate the development of intimate and romantic feelings over time. Finally, OS was also associated with a broader synaesthetic phenotype in showing significantly elevated rates of two other types of synaesthesia, grapheme-personification synaesthesia and grapheme-colour synaesthesia.

We found too that rates of diagnosed autism were over 30 times higher in OS individuals than otherwise expected (or 14 times higher even with our most conservative estimate). Differences were most associated with the Social Skills sub-scale of the AQ (finding social situations difficult or unenjoyable, with a preference for objects over humans in one AQ question). Poor inter-human relationships may be relevant to why OS individuals develop relationships with objects although it is unclear whether poorer social skills might be a contributing factor towards OS or indeed a consequence. For instance, objectum sexuals experience considerable social stigma attached to their orientation2 which could affect social skills through an avoidance of interactions with other people. Relatedly, anthropomorphizing has been suggested to be a compensatory mechanism when individuals experience increased levels of loneliness36 and autistic individuals report higher ratings of loneliness compared to controls37. Other autistic traits might also facilitate feelings of intimacy with objects: a strong need for routine might be fulfilled more easily in relationships with objects rather than people, while higher attention-to-detail and a tendency for special interests could promote heightened focus on, or appreciation for particular objects7. Finally, synaesthetic personifications may further reinforce this attention since objects with positive synaesthetic personalities are even known to bias eye-movements for synaesthetes15. Nonetheless, we point out that just over one third of OS individuals did not report a diagnosis of autism and did not score above the AQ threshold (although a number of these scored closely). It is therefore possible that autism is not a necessary prerequisite for OS in all cases. Nevertheless, our current data suggests that OS, autism, and synaesthesia are linked at multiple levels and future research could focus on delineating the precise nature of how autism and synaesthesia interact in OS.

An important methodological consideration is the fact that our OS participants were recruited from forums online. We took this approach because it would have been difficult to achieve in-person testing given that OS is rare, internationally distributed, and without any regular real-world meeting place (as far as we are aware). More importantly, our participants were reassured by the protection of anonymity, meaning that in-person testing would inevitably have reduced sample size. Importantly, one might wish to argue that recruiting from online platforms could disproportionally attract people with social difficulties (and thereby elevate AQ scores). However, we point out that the OS group scored higher than controls across all factors of the AQ (Social skills, Attention-switching, Attention-to-detail, Communication, and Imagination) suggesting that our results are not skewed by the social traits of people drawn to online forums. Relatedly, one might wish to argue that rates of autism may be a priori higher on such forums, but we point out that rates of diagnosed autism in OS individuals was almost 40%, a prevalence that is hard to explain away as the result of our online recruitment methods.

In addition to the above consideration, we note that our online methodology did not allow for us to perform clinical diagnoses of autism; we therefore took participants’ reports of autism at face-value. Nevertheless, we were careful to ask about “formal” diagnoses, and we replicated our findings on a sub-set of participants whose formal diagnoses were backed-up with substantive details (i.e., when their diagnoses had taken place). We further replicated using AQ scores (based on the autism threshold of ≥3219). Given these conservative approaches, we are confident our classifications of autism are accurate, and we also point out that our findings are replicated by our analysis of autism rates in the cohort tested by Marsh7 (see Introduction). Finally, we address one last concern, that AQ scores in OS participants could be circular, given that one question in the AQ (out of 50) could potentially define OS (i.e., the reverse-coded “I find myself drawn more strongly to people than to things”). If we remove this question from our AQ analysis we still observe the same pattern of results (i.e. OS individuals still score significantly higher on the Social skills factor of the AQ with a large effect size; and 10 OS individuals compared to 2 controls still score above the diagnostic threshold ≥32 on the AQ overall; see Supplementary Information Table S2). Nonetheless, even aside from the ‘literal’ question described above, it could be argued that high scores on the social factor of the AQ might simply reflect the social challenges of identifying as OS. Importantly however, OS individuals were elevated across all sub-scales of the AQ. We are therefore confident that our results speak to rates of autism, rather than being a circular finding about OS per se.

Our data speak to biological38, psychological39,40 and philosophical41 models of sexuality or romantic love. We inform biological theories by showing that certain sexual orientations can be found at higher rates within recognised neurodevelopmental conditions with known genetic traits10,42 and specific neurological profiles43,44 independent from the sexual orientation itself. Fifty-three percent of our OS cohort was characterised as having either synaesthesia and/or autism (from diagnosis or elevated AQ scores, with a further 9% scoring close to threshold), placing these well-understood neurodevelopmental conditions firmly at an intersection with this sexual orientation. Our data also support one very recent suggestion45 that autism might dictate sexual preference to some extent, and suggest the need for raised awareness among medical practitioners to support and promote inclusion for autistic people regarding orientation. Our data also speak to models of synaesthesia showing synergistic outcomes when synaesthesia and autism co-occur within individuals6 and they speak to the study of anthropomorphism36 by validating the use of detailed personality questionnaires46 for non-human targets. We suggest that this methodology might be further exploited to ask whether personality profiles for objects in OS (or indeed in general anthropomorphism) are random or ordered. For example, our methods could test whether object-personalities reflect the personality traits of those humans making judgements – as would be predicted if object personifications arise from mechanisms within self-other judgements16,47. Finally, our data address psychological39 and philosophical41 models of romantic love which have traditionally been defined around personhood (i.e., a feeling of pleasure derived from an attraction towards another person). Our findings suggest, crucially, that personification rather than personhood may be the necessary pre-requisite for romantic love to arise.

Our study is the first behavioural treatment of OS in the scientific literature. Although inquiry into OS has gained little traction in modern science, wider understanding would be particularly beneficial given that objectum sexuals are often marginalised for their orientation2. In summary, we have shown links between OS, synaesthesia and autism, and propose that increased anthropomorphizing in OS may sometimes occur as a result of differences in social cognition and other autism-driven traits as well as object-personification synaesthesia.