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Table 1 Overview of study measures and data collection timepoints

From: Exploring multisensory integration of non-naturalistic sounds on body perception in young females with eating disorders symptomatology: a study protocol

Measure

Description

Baseline

Experiment

1

2

Demographic data

Participants’ age. In addition, BMI will be calculated with the following formula: BMI = weight (kg)/(height (m)2) following the World Health Organization’s criterion [45]

X

  

Information consent

Written informed consent

X

  

S-EDE-Q†

To assess body EDs psychopathology. Self-administered questionnaire composed of 28 items using 7-point Likert scales ranging from 0 (not at all) to 6 points (markedly) about the previous 28 days. Four subscales are measured, including: dietary restraint (5 items), shape concerns (8 items), weight concerns (5 items), and eating concerns (5 items). For each subscale, the score ranges from 0 and 6 points. Participants will be grouped according to a global index score which is the average of the four subscale scores. As in Mond et al. [36], we will use a cut-off point ≥ 2.8 as clinically significant. Higher scores indicating a higher ED pathology. The S-EDE-Q have shown adequate internal consistency (Cronbach’s alpha ≥ .81 for all subscales), acceptable sensitivity (≥ 0.95), specificity (≥ 0.90), and positive (≥ 0.59) and negative (≥ 0.99) predictive values, and positive and significant correlation (≥ 0.70) with EDE diagnoses

X

  

HSPS‡

To assess the tendency to process stimuli and information more strongly and deeply than others (sensory-processing sensitivity). Self-administered questionnaire composed of 27 items using 7-point Likert scales ranging from 0 (not at all) to 6 points (markedly). Five subscales are measured including: (1) sensitivity to overstimulation (9 items); (2) aesthetic sensitivity (6 items); (3) low sensory threshold (5 items); (4) fine psychological discrimination (4 items); (5) harm avoidance (3 items). For each subscale, the score ranges from 27 to 189 points. Higher scores indicate higher sensitivity level. A total global score will be obtained by averaging the five subscales. The HSPS have shown adequate internal consistency (Cronbach’s alpha ≥ 0.81 for all subscales) and construct validity in the adult Spanish population

X

  

MAIA§

To measure interoceptive body awareness. Self-administered questionnaire composed of 32 items using 6-point Likert scales ranging from 0 (never) to 5 points (always). Eight subscales are measured, including: (1) noticing (3 items); (2) not-distracting (2 items); (3) not-worrying (2 items); (4) attention regulation (7 items); (5) emotional awareness (5 items); (6) self-regulation (4 items); (7) body listening (3 items) (8) trusting (3 items). It generates a total direct score that ranges from 0 to 160 points. Higher scores indicate higher interoceptive awareness. A total global score will be obtained by averaging the six subscales. The MAIA have shown adequate internal consistency (Cronbach’s alpha 0.64 to 0.83 for all subscales)

X

  

Auditory trials

Presented in four conditions: an anchor task (20 trials); a practice task (3 trials); an experimental block (30 trials) and a questionnaire block (3 trials)

 

X

X

Estimation of body position (finger/waist)

To assess estimation of location or position of fingertip/knuckle (allowing to calculate the estimated finger length can be calculated) and waist width after each auditory experimental trial

 

X

 

Confidence task

It has been found that the reliability of perception might be linked to subjective rather than objective accuracy [41]. For example, previous studies using body illusions report that confidence was not accompanied by increases in objective accuracy (i.e., [42, 43]). Therefore, to assess the reliability of their estimations, after each auditory experimental trial, the feeling of confidence with the estimation of body part position will be explicitly assessed by asking the participants: “From one to seven, how confident are you of your estimation?” (7-point Likert scale)

 

X

X

Body feelings questionnaire (finger/waist) [25]

To assess subjective feelings about their finger/waist after the trials (susceptibility to the illusion). Participants will respond to a questionnaire containing 7-point Likert-type response items ranging from 1 (strongly disagree) to 7 (strongly agree) (Finger: 14 items; Waist: 13 items). In addition, a range of figures representing finger/waist will be presented. Each figure shows a whole hand/trunk selectively shrunk or elongated. Participants will be asked to choose one of the figures to describe the subjective feeling of the size of their finger/waist when listening to the sound. [see Additional file 2 and 3 for more details]

 

X

X

Body visualizer task [44]

To assess the ability to accurately estimate body size (body size discrepancy) as well as the effects of sound feedback on perceived body size. Participants will adjust the weight related dimension of the body of a 3D avatar displayed on the screen to correspond to their perceived body size. Accuracy will be calculated according to the formula (estimated/actual body size) × 100 also-called body perception index (BPI) [45]. Specifically, a negative value represents an underestimation, whereas a positive value represents an overestimation

X

 

X

  1. Body weight will be measured to the nearest 0.1 kg/% by means of a calibrated digital body fat scale (Sinocare CW 286). The Body feelings questionnaire will be directly built into Google Form and completed on a 10.1″ Android tablet (Lenovo M10)
  2. Spanish Version of the Eating Disorder Examination Questionnaire [46]
  3. Spanish version of the Highly Sensitive Person Scale [47]
  4. §The Multidimensional Assessment of Interoceptive Awareness [48]