Expectations on the severity and frequency of intrusions are increased while expectations on the controllability of intrusions are decreased.

Expectations on the severity and frequency of intrusions are decreased while expectations on the controllability of intrusions are increased.

Expectations on the severity and frequency of intrusions and on the controllability are neither increased nor decreased.

Participants are watching a video tape of a trauma expert who provides selective information on the development of intrusive memories. This video tape aims to increase positive expectations.

Participants are asked to complete a pen-and-paper diary 7 days in a row, reporting on intrusive memories in reference to the trauma film. They are asked to state the number of intrusions per day; each day of the diary is labeled and split into three sections (morning, afternoon, evening), and they are asked to mark in a box in the appropriate section when they experienced an intrusion. For each intrusion, they indicate the quality of the intrusion (image, thought or both), the intensity of and distress caused by the intrusion both on a scale ranging from 0 ("not at all") to 10 ("extremely"), the content of the intrusion, and the situation in which the intrusion occurred. Intrusive memory frequency across 7 days are calculated, whilst higher sum scores represent more intrusions. Severity of intrusions are calculated by combining the average score of the intensity and distress scale across all intrusions, whilst higher values indicate higher intensity/distress of reported intrusions.

Participants are asked to respond 22 items in reference to the trauma film (e.g., "Pictures about the film popped into my mind.") by indicating how often each reaction occurred during the past seven days with respect to the film they watched last week. Items are rated on a 4-point-Likert-scale ranging from 0 ("not at all"), 1 ("rare"), 3 ("sometimes") to 5 ("often"). The IES-R consists of three subscales: "intrusion", "hyperarousal", and "avoidance". The total score (sum score for the total scale comprising the sum scores of all three subscales) is calculated ranging from 0 to 110 with higher values represent a worse outcome, i.e., higher total distress due to the trauma film in the past week. In addition, the sum score for the intrusion subscale is separately calculated ranging from 0 to 35 (Items 1, 3, 6, 9, 14, 16, 20) with higher values represent more intrusions due to the trauma film in the past week.

The Appraisals of Intrusions Questionnaire is 25-item measure that assesses metacognitions of intrusive thoughts and memories. Participants rated the strength of each belief when they experienced their intrusive memories on a scale ranging from 0 (I didn't believe that at all.) to 100 (I was completely convinced that this was true.). Metacognitive appraisals are divided into four categories: "necessity of control", "external consequences", "psychological problem" and "negative self-evaluation". A total score is calculated, whilst higher values indicate more dysfunctional metacognitive beliefs.