The Association Between Physical Sensations and Thinking Styles

The Priming Paradigm measures panic related associations. During this task, participants will be instructed to sort target words as words versus non-words (lexical decision task). Before a target appears, however, a prime will be presented. Participants will be instructed to look at the prime but to not react to it. Following the design of Hermans et al. (2010), we will use the following prime-target combinations: panic-panic, panic-neutral, neutral-neutral, neutral-panic. There will also be prime-target combinations with non-words as targets.

The Single Target Implicit Association Test (STIAT) measures the associative strength between a target concept and two attribute dimensions. Participants are asked to sort stimuli into three categories by means of two response keys: one category represents a target concept, and two categories represent two poles of an attribute dimension. The target category is paired with both attributes. The present STIAT is designed as follows: targets: bodily changes, attributes: alarming vs. meaningless, and it takes over the structure as suggested by Wigboldus et al. (2006): (a) attribute discrimination, (b) target categorization practice, (c) first combined block, (d) reversed target categorization practice, and (e) reversed combined block.

The Scrambled Sentence Task (SST, Wenzlaff & Bates, 1998) measures panic-related interpretation biases. It consists of six-word strings participants are asked to unscramble to form a five-word sentence, leaving out one word. The present SST can be completed such that the resulting five-word sentences produce either a panic-related or neutral interpretation. During the SST, there is a cognitive load, i.e., participants have to memorize a 6 digit number.

The Interpretation Bias Questionnaire (IBQ) measures panic-related interpretation biases. It consists of 18 brief scenarios used in earlier studies (Ebert, 1993, Foa & McNally, 1987). Nine items describe panic-related situations, and the other nine describe negative, threat-related situations. Following each scenario, three explanations are presented (for panic-related scenarios: one panic-related explanation and two panic-unrelated explanations, for negative, threat-related situations: one very negative, threat-related interpretation and two harmless explanations). Participants have to indicate how likely each explanation for the corresponding scenario is, using rating scale from 0 (not likely) to 100 (very likely).

The ASI (Ehlers, 1986; Reiss, Peterson, & McNally, 1986) is a 16-item self-report questionnaire measuring fear and concerns regarding anxiety-related symptoms such as "It scares me when my heart beats rapidly". Items are rated on a five-point Likert scale (0 = "Very little" to 4 = "Very much").

The DASS-21 (Lovibond & Lovibond, 1995; Nilges & Essau, 2015) questionnaire comprises three 7-item subscales assessing levels of depression, anxiety, and stress.

The ACQ (Chambless, Caputo, Bright, & Gallagher, 1984; Ehlers, Margraf, & Chambless, 1993) measures maladaptive thoughts about the potential for disastrous consequences arising from anxiety or panic. It includes 14 items which can be scored as a total scale, or according to its two subscales, "loss of control" and "physical concerns".

The BSQ (Chambless, Caputo, Bright, & Gallagher, 1984; Ehlers, Margraf, & Chambless, 1993) includes 17 items that reflect specific bodily sensations (e.g., heart palpations, dizziness). Participants are asked to indicate the degree to which they experience anxiety related to these sensations by means of a five-point Likert scale (1 = "Not at all" to 5 = "Extremely").

The PDSS (Shear et al., 1997) is a 7-item scale and provides a composite severity score of frequency, distress, and impairment associated with panic attacks.

The MI (Chambless, Caputo, Jasin, Gracely, & Williams, 1985, Ehlers, Margraf, & Chambless, 1993) consists of 26 items and measures agoraphobic avoidance using a five-point Likert scale (1 = "Never avoid" to 5 = "Always avoid"). Each item has to be answered twice, once for when being accompanied and once for when being alone.

A symptom checklist will assess the presence of panic-relevant symptomatology in line with the DSM-5 criteria for panic disorder, e.g., occurrence and frequency of panic attacks, experienced distress during panic attack, fear of going crazy, dizziness etc. (for a similar procedure, see Wilhelm, Gerlach, & Roth, 2001). It also assess participants' level of generally anxiety and whether or not participants experienced a panic attack. This will be completed repeatedly within each testing session.

An adapted version of the procedure described by Kossowsky, Wilhelm, and Schneider (2013) and Wilhelm et al. (2001) will be used in the present study. During the hyperventilation, participants will breathe through their nose and their breathing will be monitored by a capnograph. There will be 3 phases.

Phase 1: Participants will undergo a 'paced breathing' procedure. That is, they will be asked to keep a breathing speed of 18 cycles/minute (breaths per minute, bpm). Breathing speed will be paced by computerized audio instructions. At the end of phase 1, the end-tidal CO2 level should be 25mmHg (for recommendations for the end-tidal level, see Meuret et al., 2005).

Phase 2: The goal of this phase is to maintain the 25mmHg CO2 level while participants keep on breathing with a 18 bpm paced breathing pattern.

Phase 3: This is a 3 minute recovery phase. During this phase, participants are supposed to breath normally again.

An Electrocardiogram (ECG) will assess heart rate variability (HRV) during each testing session

An Electromyography (EMG) will assess facial muscle activity during each testing session.

Following recommendations of Ritz and Dahme (2006), the HRV assessment will be combined with a respiratory assessment. Respiration will be assessed by means of two plethysmography belts (thorax and abdomen) during each testing session.

Electrodermal activity (EDA), i.e., variations in the electrical characteristics of the skin, will be assessed during each testing session.

Saliva samples will be collected at the start, during, and at the end of each testing session to analyze changes in cortisol levels, which serve as indices of arousal and stress.

Saliva samples will be collected at the start, during, and at the end of each testing session to analyze changes in alpha amylase, which serve as indices of arousal and stress.