investigate the role of self-control in relation to mindfulness and eating behaviour. Self-control can be defined as a subset of self-regulatory processes that aim to override prepotent
impulses. Self-control concerns the capacity to reduce discrepancies between goal states and current behaviour in situations where they conflict. Although the studies in this thesis do not provide direct evidence for a mediating role of self-control in determining eating behaviour as a function of mindfulness, they are restricted in a number of ways that may be addressed in further research. These include limitations of the Attentional Control Scale, the use of cueing manipulations, and the highly specific nature of the goal accessibility task.
In investigating self-control, I focused on the role of executive function, in line with the model proposed by Teper et al. (2013) which outlines how mindfulness increases self-control ability via improvements in executive function. In Studies 2 to 4 I used the Attentional Control Scale (ACS) to assess executive function ability. The ACS is a self-report measure of executive function with a two-factor structure, the focusing subscale refers to the ability to maintain attention while inhibiting attentional capture by distractors, the shifting subscale assesses ability to redirect attention between tasks. This structure maps onto the three executive functions of updating, shifting, and inhibition proposed in Miyake et al.’s (2000) influential framework. Accordingly, the ACS predicts performance on numerous indicators of these
executive function abilities including maintenance of task goals, inhibition of responses, and task switching on an anti-saccade task (Judah et al., 2014), rate of inhibition errors on a Go/No- Go task (Wiersema & Roeyers, 2009), and attentional focus and inhibition on the Flanker task (Reinholdt-Dunne, Mogg, & Bradley, 2013).
Although the ACS does predict inhibition on executive function task assessments, the items of the focusing subscale, the subscale most relevant to inhibition (Judah et al. 2014), pertain primarily to attentional focus and ability to inhibit attentional capture by irrelevant information rather than inhibition of response. It is the inhibition of prepotent responses that is the primary feature of inhibition as defined by Miyake et al. (2000), and highlighted by Teper et al. (2013). Whether the ACS is uniquely predictive of inhibitory executive function to a large enough extent to accurately test the hypotheses derived from Teper et al.’s model in the current studies require further consideration; it should be noted that the focusing subscale did not provide a predictive advantage over the shifting subscale in any of the studies included in this thesis. An alternative approach to investigating the role of self-control, as conceptualised in Teper et al.’s model, may be to use task measures of executive function that are specifically tailored to investigating inhibition. Two such measures are the Stroop Task (Stroop, 1935) and the Go/No-Go Task (see e.g., Lustig, Hasher, & Zacks, 2007). The Stroop Task requires
participants to name the colour of ink that words are presented in, these words may represent the congruous colour to the ink (e.g. blue written in blue ink) or be incongruous with ink colour (blue written in green ink). Correctly naming ink colour requires inhibition of prepotent
impulse to read the word rather than name the colour and involves cognitive functions of response inhibition, interference resolution, and behavioural conflict resolution (Adleman et al., 2002). The Stroop Task has been used to study executive function in a range of cohorts (Zysset, Müller, Lohmann, & von Cramon, 2001), producing large and reliable effects
(MacLeod, 1991). Furthermore, poorer response inhibition as assessed with the Stroop Task is associated with greater BMI and adiposity (Deng et al., 2018; Stinson, Krakoff, & Gluck, 2018).
press, when certain targets are presented and withhold response when non-targets or distractors are presented, the go response is trained over multiple trials to be the prepotent response and false alarms (go responses on no-go trials) are used as the primary outcome measure. This task allows for investigation of response inhibition under conditions in which other cognitive/behavioural processes are minimised (Simmonds, Pekar, & Mostofsky, 2008), and may be used to examine impulsive responses to food stimuli (Meule, 2017).
In addition to my studies that used the Attentional Control Scale to measure self- control, in Studies 4 to 6 I aimed to investigate self-control processes using methods that were less dependent on assessment of executive function, and instead focused on self-control in a more dietary context specific manner. In Studies 4 and 5 I used a food cueing paradigm to manipulate the need for self-control and so infer self-control ability, but found no evidence of an effect of the cueing manipulation. In Study 6 I used a task measure intended to assess self- control ability specifically in the context of dietary behaviour. This goal accessibility task involved a priming procedure in which the degree of cognitive activation of dieting goals in response to food primes gives an indication of the level of self-control specific to eating behaviour. This task is based on the principles of Counteractive Control Theory (Trope & Fishbach, 2000) and relies on testing the strength of automatic associations between food stimuli and goal representations that develop as a result of multiple pairing of temptation and self-control (Fishbach et al., 2003). However, the results of Study 6 showed that more mindful people actually exhibited slower responses to dieting words, suggesting more deliberative, rather than automatic, responses. This result is consistent with Brown and Ryan’s (2003) time interval hypothesis, which proposes that mindfulness creates an interval in which individuals are able to observe their own behavioural choices rather than acting in an automatic manner, and with additional studies that suggest more deliberative responding on attentional tasks as a function of mindfulness (Di Francesco et al., 2017; Rodriguez-Vega et al. 2014). To build on this finding, further research may utilise context dependent measures of self-control that do not assess automatic self-control processes, but instead focus on deliberative actions.
One approach may be to assess the degree to which mindful people are able to ‘think cool’ when presented with goal conflict events. Based on delay of gratification research, in which participants must resist immediate tempting stimuli, Metcalfe and Mischel (1999) proposed a dual-process model in which self-control is governed by interacting ‘hot’ and ‘cool’ systems. The hot emotional system reacts to appetitive and fear inducing stimuli to trigger impulsive responding, while the cool system is a cognitive, reflexive system which overrides hot responses to provide self-control. Cool generated ideation in the face of tempting stimuli, or ‘thinking cool’, involves self-generated thinking about and cognitive transformations of the stimulus to access its cool properties. This thinking allows dominance of the cool system, representing greater self-control and increasing the ability to keep goals in mind and monitor progress in attaining them when presented with goal conflict events.
In a body of work that has developed since the inception of this thesis, the construct of decentring as a component of mindfulness has been investigated based on similar principles to those of ‘thinking cool’. Based on grounded cognition principles (Barsalou, 2008), Papies and colleagues (e.g., Papies, Pronk, Keesman, & Barsalou, 2015; Papies, van Winckel, & Keesman, 2016) have proposed that exposure to appetitive foods triggers reward simulations of eating and enjoying foods, based on previous experiences. These eating and reward simulations contribute to craving and desire, but applying a decentred perspective, in which thoughts are viewed as transient, may make the reward simulation less subjectively real and prevent the development of full-blown craving and desire. Food specific experiences of decentring, for example, the ability to distance oneself from thoughts about food, have been shown to be associated with reduced instance of food craving in experienced meditators (Papies et al., 2016), and a brief training exercise in which participants were taught to take a decentred perspective when viewing images of food resulted in healthier food choices and reduced energy intake in a student sample (Papies et al., 2015). It appears then that investigation of thought processes and mental representations of attractive environmental stimuli, and the
role that they play in determining control over behaviour in more and less mindful individuals represents a promising avenue for further research.
6.2.2 Non-conflict driven self-regulation. Self-control represents just one aspect of