Scientific Background

The BRO test is based on the discovery by Pettigrew and Miller (1998) that binocular rivalry is slower in persons with bipolar disorder than in controls. A follow-up paper (Miller et al, 2003) replicated the finding and extended the research, showing that binocular rivalry did not appear to be slower in subjects with schizophrenia or major depression (disorders commonly misdiagnosed as bipolar disorder, and vice versa), though some individuals in these groups and in non-clinical controls did appear to exhibit slow rivalry. The slow rivalry trait does not appear to be affected by a participant's clinical state or medication, though these issues require further investigation (see Ngo et al, 2011 and some additional relevant studies listed on the References page).

Pettigrew and Miller (1998) proposed that slow binocular rivalry might represent a trait marker, or "endophenotype" for bipolar disorder that can be used in genetic studies to help identify genes that contribute to development of the disorder (see also Ngo et al, 2011). This proposal received support from a large twin study (Miller et al, 2010) that showed a substantial (~50%) genetic contribution to an individual's rate of binocular rivalry.

Comprehensive reviews of this work, with proposals for related research, can be found in Miller et al (2012), Ngo et al (2013) and Miller (2020), available on the References page. Independent replication studies include Nagamine et al (2009), Vierck et al (2013) and Zhu et al (2013). These citations can be found on the References page. A detailed resource on binocular rivalry research (Miller, ed, 2013) is available at:

https://benjamins.com/#catalog/books/aicr.90/main

In order to fully examine the genetic and clinical diagnostic utility of the slow binocular rivalry trait, as well as related issues such as potential effects of medication and clinical state, large-scale studies are required. This has led to development of the BRO test (see About BRO). To examine the range of methods for eliciting binocular rivalry, with a view to identifying the method most suitable for online testing, a review of the literature was conducted (Law et al, 2013).

Studies to examine whether eye movements could potentially explain or confound an individual's binocular rivalry rate were conducted and suggest eye movements do not explain or confound the trait (Law et al, 2015; Law et al, 2017a). To examine stimulus properties for potential use with BRO, a study with healthy persons was performed (Law et al 2017b). Following this study, to ensure the BRO test presentation method (anaglyph glasses) elicits slow binocular rivalry in bipolar disorder, comparable to that with our previously used stimuli, a comparative study was conducted with both persons with bipolar disorder and control participants (Law et al, in preparation). A full description of the BRO test method, and means of ensuring accurate responses from subjects when tested online, will also be forthcoming. All of our published binocular rivalry studies are available on the References page.

The finding of slow binocular rivalry in persons with bipolar disorder also has important mechanistic implications concerning the pathophysiology of bipolar disorder. For full details of such implications, see Miller (2020; available on the References page).