TABLE 1.

Types of possible investigation and possible dependent variables in the study of iconic gestures in comprehension.

Methodological aspects	Possible variations
Investigation	– Behavioral (Beattie and Shovelton, 2002). – Electrophysiology (Wu and Coulson, 2007a). – Transcranial magnetic stimulation (Zhao et al., 2018). – Transcranial direct current stimulation (Cohen-Maximov et al., 2015). – Functional magnetic resonance imaging (Holle et al., 2008). – Magneto encephalogram (Drijvers et al., 2018). – Eye tracking (Beattie et al., 2010).
Gesture-speech integration	– Implicit (Sekine et al., 2015) or Explicit (Perrault et al., 2019).
Task during stimuli presentation	– Passive observation (Habets et al., 2011). – Dual task paradigm (Wu and Coulson, 2014). – Lexical decision (So et al., 2013). – Attentional task (Green et al., 2009). – Target relatedness task (Ping et al., 2014). – Stroop-like task (Kelly et al., 2010a).
Attention during stimuli presentation	– Speech. – Gesture (Bohn et al., 2020). – Stimuli as a whole (Vogt and Kauschke, 2017). – Unrelated aspect (Kelly et al., 2010a).
Type of iconic gesture	– Action (Stanfield et al., 2013). – Physical attributes (Dick et al., 2009). – Position (Beattie and Shovelton, 2002). – Typical vs. Atypical (Dargue and Sweller, 2018b).
Gesture-speech relationship	– Redundant (Holler et al., 2009) or Complementary (Kelly et al., 2004). – Congruent vs. Incongruent (Wu and Coulson, 2005). – Presence vs. Absence (Iani and Bucciarelli, 2017).
Type of stimuli	– Video clips (speech + gesture) (Kelly et al., 2010b). – Soundless video clips (Novack et al., 2016) – Live gestures (Kartalkanat and Göksun, 2020). – Target words/pictures (Bernardis et al., 2008; Wray et al., 2016). – Cartoons (Wu and Coulson, 2005).
Stimuli content	– Sentences (Momsen et al., 2020). – Single words (Sekine et al., 2020). – Narration (Macoun and Sweller, 2016). – Visual stimuli (Aussems and Kita, 2019).
Gesture length	– Full gesture (Kelly et al., 2007) or Stroke (So et al., 2013).
Origin of gesture	– Spontaneous (Holle et al., 2010) or Scripted (Holler et al., 2015).
Visibility of actor	– Knees up (Wolf et al., 2017). – Waist up (Dick et al., 2014). – Torso (Zhao et al., 2018). – Visible (Green et al., 2009) or Masked face (Zhao et al., 2018).