Laterality indices consensus initiative (LICI): A Delphi expert survey report on recommendations to record, assess, and report asymmetry in human behavioural and brain research

Laterality indices (LIs) are used to quantify the left-right asymmetry of a wide range of brain and behavioural variables and to provide a single measure that is statistically convenient and seemingly easy to interpret. However, there is substantial variability in how structural and functional asymmetries are recorded, calculated, and reported, suggesting little agreement on the conditions required for its valid assessment. The present study aimed for consensus on general aspects in this context of laterality research, and more specifically within a particular method or technique (i.e., dichotic listening, visual half-field technique, performance asymmetries, preference bias reports, electrophysiological recording, functional task-related MRI, structural MRI, and functional transcranial Doppler sonography). Experts in laterality research were recruited by snowball sampling and invited to participate in a three-round online Delphi survey to evaluate consensus and stimulate discussion. In Round 0, 106 experts generated 453 statements on what they considered good practice in their field of expertise. A team of moderators organized the statements into a 295-statement survey that the experts then were asked, in Round 1, to independently assess for perceived importance and their level of support, and further reduced the survey to 241 statements that were presented again to the experts in Round 2. Based on the Round 2 input, we present a set of critically reviewed key recommendations to record, assess, and report laterality research for various methods.