## 2 Materials and Methods
### Instruments and Variables  
_Sociodemographic information and dart-throwing experience._ During the screening phase, an ad hoc interview was conducted to collect basic sociodemographic information including year of birth, gender, the existence of diseases and medications that could interfere with participation, and dart-throwing experience of the participants. It was not a standardized interview, but one developed specifically for gathering the relevant information needed for this particular research. To evaluate the level of experience in dart-throwing, participants were asked to answer two questions: (1) to indicate their experience in dart-throwing on a scale from 0 (I have never played darts) to 10 (I have a lot of experience, I even compete, equivalent to several years of regular practice), and (2) they were asked: 'Approximately how many times do you estimate that you have played darts in the last two years? (Less than 5 times, between 6 and 15 times, between 16 and 25 times, more than 25 times)'.  
_Self-Efficacy._ This was measured using the General Self-Efficacy Scale (GSS) [34; 35], which was also administered during the screening phase. This scale assesses the stable feeling of personal competence to handle stressful situations. Higher scores reflect greater perceived self-efficacy. The scale consists of 10 items (e.g., item 2.--\"I can solve difficult problems if I try hard enough\") with 4-point Likert-type response scales. (1.--\"Not at all true\", 2.--\"Barely true\", 3.--\"Moderately true\" and 4.--\"Exactly true\"). In the present study, the scale yielded a Cronbach's alpha coefficient of 0.74. This allowed for controlling for the possible influence of self-efficacy on subsequent performance, as self-efficacy resulting from experiences during the practice of a motor task is found to predict performance in subsequent motor learning tests [14; 16] or performance [36; 37].  
_State anxiety._ We used the State Anxiety subscale of the State-Trait Anxiety Inventory (STAI) [38], and it was measured before proceeding with the dart-throwing. This subscale consists of 20 items (e.g., item 1.--\"I feel calm\") with 4-point Likert-type response scales (0.--\"Not at all\", 1.--\"Somewhat\", 2.--\"Quite a lot\" and 3.--\"Very much\"). In this study, this scale yielded a Cronbach's alpha of 0.86. Anxiety has been found to exert a relevant influence on both motor learning and motor performance [39].  
_Dart preference and forced allocation._ Before the start of throwing, to control for the influence that forced allocation or lack of choice and dart preference may have on the performance and outcomes of a motor task [40; 41], participants were asked to rank five darts based on their preference for the color and pattern of the dart feather. The scale ranged from 0 (least liked) to 4 (most liked). Then, before starting the throws, they were allowed to choose between the darts ranked 3-4.  
_Attentional focus and perceived pressure._ The effect of attentional focus [2; 42; 43] was controlled at the end of Phases 2, 3, and 4 when participants were asked about where they had focused their attention during the throws, using the following question: \"In this phase, during the dart throws, where did you focus your attention: (a) on the dartboard, where you wanted to aim the dart (External Focus); (b) on the arm-hand position, the sensations and movement of the body and arms (Internal Focus); and (c) mixed, alternating between both (Mixed Focus)\". At the same time, and to assess whether the pressure to achieve the maximum number of points was influenced by the information received, they had to quantify this pressure on a scale that ranged from 0 (\"I didn't notice any pressure\") to 10 (\"I noticed a lot of pressure\"). Perceived pressure has been found to exert a relevant influence on motor performance [3].