Tuesday, April 30, 2019

Thought-Control Failure: Sensory Mechanisms and Individual Differences

Measuring Thought-Control Failure: Sensory Mechanisms and Individual Differences. Eugene L. Kwok et al. Psychological Science, April 22, 2019. https://doi.org/10.1177/0956797619837204

Abstract: The ability to control one’s thoughts is crucial for attention, focus, ideation, and mental well-being. Although there is a long history of research into thought control, the inherent subjectivity of thoughts has made objective examination, and thus mechanistic understanding, difficult. Here, we report a novel method to objectively investigate thought-control success and failure by measuring the sensory strength of visual thoughts using binocular rivalry, a perceptual illusion. Across five experiments (N = 67), we found that thought-control failure may occur because of the involuntary and antithetical formation of nonreportable sensory representations during attempts at thought suppression but not during thought substitution. Notably, thought control was worse in individuals with high levels of anxiety and schizotypy but more successful in mindful individuals. Overall, our study offers insight into the underlying mechanisms of thought control and suggests that individual differences play an important role in the ability to control thoughts.

Keywords: thought suppression, thought substitution, binocular rivalry, mental imagery, mindfulness, open data

The ability to control our own thoughts, is an important mental capacity and is important for attention, focus, future planning and ideation [1-4]. Given that up to 80% of the general population experience some form of unwanted intrusive thoughts [5], the ability to control thoughts is also an important determinant of mental wellbeing [6]. Indeed, failure to control thoughts has been linked to various mental disorders including anxiety[7, 8], obsessive-compulsive disorder (OCD) [9, 10] and schizophrenia [11, 12].

Since the work of Freud, the idea of voluntarily repressing a thought, thought suppression, has become an active phrase in the general populace and has attracted muchattention, despite the lack of any clear objective methodology to investigate the phenomenon. Attempting to control thoughts by direct thought suppression (not thinking about a given thought) is often difficult and subjective reports suggest suppression mostly fails [6]. Instead of directly eliminating thoughts from the mind, reports suggest suppression paradoxically leads to heightened preoccupations with these thoughts [13]. For example, individuals instructed to suppress the thought of a white bear are often unable to do so and report intrusions of the thought inadvertently arising a short time later [14]. Research into thought suppression failure (e.g. [15-20]) and its consequences have been studied in a wide variety of domains including organisational behaviour [21], smoking addiction [22], immune function [23] and psychopathology [24-27]. However, largely due to the inherent private subjectivity of thought suppression, its existence as a possible process, dynamics, where and why such suppression failures originate, remains largely unknown. While thought suppression is the most commonly studied thought control strategy, other forms of thought control have been examined and seem to be more effective. For example, thought substitution, in which a suppressed thought is instead replaced by a substitute thought, has shown evidence for reduced thought intrusion frequency and thought control failure [6, 14, 28]. More recently, mindfulness has shown evidence as an effective form of mental control [29].

While these forms of thought control seem more effective than direct thought suppression, without a mechanistic understanding of these processes, research into why one method might work over another, and indeed if there are potentially more effective methods remains limited.

Wegner [13] first attributed the inability to control thoughts using thought suppression to the interaction between two practical, but simultaneously conflicting, mental processes. The first involves a conscious process that attempts to achieve a state of mind free from the to-be-suppressed thought. The second is an unconscious monitoring process that checks for unwanted instances of the to-be-suppressed thought. Wegner proposed thoughts unwillingly enter consciousness due to the ironic opposition between these two processes, ultimately leading to thought control failure. Neuroimaging evidence has generally supported this view [30-32]. However, while mechanisms have been proposed, the empirical investigation and objective measurement of thought control has been limited.

The inherent subjectivity of thoughts has further made the objective examination of thought control difficult. For the most part, previous research has used subjective self-reports to examine thought control ( e.g. [14, 28, 33, 34]). While self-report measures have provided valuable insight into the examination of thought control, these measures may be prone to bias, experimenter demand or social desirability effects [35], and thus make it difficult to examine the underlying mechanisms.

To overcome this subjectivity and to shed light on the underlying mechanisms of thought control and its failure we devised a novel method to objectively study the control of visual thoughts using the illusion binocular rivalry. Binocular rivalry is a visual illusion that arises when two different images are presented one to each eye, inducing bistable perceptual alternations between the two images [36]. Binocular rivalry has been used to objectively measure the sensory strength of mental images [37-40] and prior perceptual stimuli [37, 39, 41]. Here we devised a novel method to utilise a brief binocular rivalry presentation to objectively assess visual representations that might emerge during attempts at thought control.

In each trial, we instructed participants to either imagine, suppress or substitute the thought of a red or green coloured object, before being presented with a brief red-green binocular rivalry stimulus. Any priming for imagined, suppressed or substituted thoughts could then be calculated to provide an objective measure of the sensory strength of these visual thought representations. To probe subjective metacognition of thought control, we instructed participants to report when thought control failed and compared these subjective reports to their level of rivalry priming. Lastly, a Thought Control Index was devised to investigate the relationship between thought control and four psychological traits: anxiety, obsessive-compulsive tendencies, schizotypy and mindfulness.

Results showed suppressed thoughts led to binocular rivalry priming significantly above chance (50%) and almost as strong as priming for intentionally imagined thoughts, indicating a failure to control the sensory trace of thoughts using thought suppression. Surprisingly, priming for trials reported as successfully suppressed was still significantly above chance, suggesting the possibility of emergent non-conscious sensory representations during attempts at thought control. Thought substitution was more, although not completely effective, in controlling the sensory trace of visual thoughts. Individuals with high trait mindfulness exhibited greater levels of thought control, whilethose with high anxiety or schizotypy traits exhibited lower levels of thought control. Interestingly, there was no relationship with obsessive-compulsive tendencies. Our data suggest that thought control failure is linked to the formation of sensory representations during attempts at thought control.

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