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The clinical literature predominantly usesthe Intrusive Memory Interview

(Hackmann et al., 2004) to measure personally experienced intrusive memories. In this methodology, participants make retrospective assessments of the number of memories they have experienced over the past 7 days (Newby & Moulds, 2011a; Williams & Moulds, 2007c; Williams & Moulds, 2008b). Conversely, the involuntary memory literature primarily uses diary measures to study memory characteristics (Berntsen, 1998; Berntsen, 2001; Watson, Berntsen, Kuyken, & Watkins, 2013). Furthermore, when memory frequency is not the focus of the study, participants are often only asked to record first two involuntary memories they experience in a given day, until they have recorded a total of fifty memories. This is done as an attempt to reduce potential demand effects, for example artificially inflating the number of involuntary memories participants experience (Berntsen, 1998; Watson et al., 2012). Other times, involuntary memory studies use a two-structured approach where participants complete a small set of questions immediately after the memory, and a larger set of questions at a later time that suits them. This is done to reduce time

demands of the diary methodology and try to ensure, as far as possible, that participants comply with the task instructions (Berntsen, 2011).

There are advantages and limitations to the reliability of both retrospective and diary measures. For example, retrospective ratings may be distorted, especially in the presence of low mood (Beck, 1979) or stressful memories (Buchanan, 2007). Additionally, Rasmussen, Johannessen, and Berntsen (2014)suggest that as

involuntary memories are often experienced briefly and pertain to everyday events, retrospective assessments may easily underestimate the frequency of these memories. However, as noted above, diary measures are also potentially inaccurate if

participants do not comply with the instructions, for example because they had an involuntary memory at a time it was not convenient to record the details, or if they forgot to. Furthermore, Verwoerd et al. (2008) argue that the number of memories recorded in a diary may to some extent reflect an individual’s ability to keep the goal of recording memories in mind, resulting in a higher number of memories being recorded by individuals high in attentional control. On the other hand, they also suggest that asking participants to keep a diary may artificially increase the number of intrusive memories experienced, because it may increase the activation of the

memory. Their results support this second proposal; participants who kept a diary about their film-induced intrusive memories recorded three times as many as participants who retrospectively reported their memories. This finding has

implications for the question of potential deficits in cognitive control. For example, Verwoerd et al. (2008) found that attentional control only predicted film-related intrusive memories in a group instructed to keep a diary of their intrusive memories. There was no relationship between participants who were asked to retrospectively

report on their intrusive memories. This suggests that keeping a diary did

meaningfully impact frequency of the memories. To address this trade-off, and to ensure frequency estimates are as accurate as possible, the diary method will be used in all three investigations into cognitive control and intrusive/involuntary memory experience, specifically to assess frequency of negative involuntary memories (chapter four and six) and involuntary memories (chapter five). In addition, the retrospective measures of intrusive memories will be used to assess the frequency of intrusive memories in chapters four and six. Chapter five, which investigates a potential link between cognitive control and involuntary memory (regardless of the valence of the memory) will only use the diary methodology, as to my knowledge there are no validated retrospective measures of involuntary memories.In this study, however, given thepossibility that participants will not fully comply with instructions to record all of their involuntary memories, they will be asked at the end of the

procedure to estimate the number of memories they experienced, but did not write in the diary, for any reason.The properties of the measures used to index these aspects of intrusive and involuntary memories are summarized below.

Intrusive Memory Interview (IMI, Hackmann et al. (2004)):

The IMI will be used to measure the frequency of intrusive memories in chapters three, four and six. It is verbally administered and addresses participants’ subjective

experience of negative ‘spontaneous’memories experienced over the past 7 days.

Participants are given a definition of a spontaneous memory and are asked about the frequency of intrusions, along with content and sensory information concerning the memory. Participants rate various memory features on a scale of 0 (not at all) to 100 (very much), including distress, sense of nowness, interference with daily activities.

Participants also rate the vantage perspective of the memory from -3 (completely first person) to +3 (completely third person). If participants experience intrusive memories about more than one event, subsequent questions are answered in relation to the most intrusive or most distressing of the memories.

Diary of intrusive/involuntary memories:

Diary measures will be used to assess both intrusive and involuntary memories in chapters four, five and six. The booklet consists of a small number of questions for each intrusive/involuntary memory they experience over a 7-day period, based on work by Berntsen and colleagues (Berntsen & Hall, 2004; Watson et al., 2012). Participants were told this could include any intrusive or involuntary memory they experienced; it was not restricted to the memory talked about in the initial session. Participants are asked to provide a short description of the memory, rate their current mood on a 5-point scale (0 very bad to 5 very good) and indicate whether the memory affected their mood (my mood became better/worse/uninfluenced). As an attempt to reduce demand effects as far as possible, participants are told not to worry if they do not experience any intrusive or involuntary memories over the week, and also that they should not feel obliged to record any details they did not want to. In addition, for the involuntary memory study (chapter five) participants will be asked to rate the valence of the memory on a scale from 0-5 (0 representing an extremely negative memory, 5 representing an extremely positive memory). See Appendix A for examples of an intrusive/involuntary memory diary page.

Compliance questionnaire:

This measure will be used in the involuntary memory study (chapter five). After handing in their diaries,participants are given a questionnaire which asked them to estimate the number of times they experienced a memory that they could not put into words, the number of times they experienced a memory when it was impractical to record details of the memory and the number of memories they did not report for any other reason. No other detail of the memory was asked, therefore this measure allows

participants to include memories they did not want to disclose any specific details about. The total number of memories indicated on this questionnaire was added to the number of memories recorded in the diary to form a summative measure of

involuntary memories. See Appendix B.