“… Ellis et al, 2006 ; Perlstein et al, 2003 ; Silberstein et al, 2001 ), and tonic states of vigilance ( Silberstein et al, 1990 ) among other factors (reviewed in Norcia et al, 2015 ; Vialatte et al, 2010 ). Of these possible explanations, we considered one of the likeliest candidate interpretations, in this experimental paradigm in particular, to be that SSVEP responses primarily reflect fluctuations in the allocation of attention ( Mora-Cortes et al, 2018 ). Indeed, attention increases the likelihood of PFI in psychophysical experiments ( De Weerd et al, 2006 ; Lou, 1999 ) and SSVEP amplitude has been extensively validated as a measure of attention to a flickering stimulus ( Ding et al, 2006 ; Hillyard et al, 1997 ; Kashiwase et al, 2012 ; Kim et al, 2007 ; Morgan et al, 1996 ; Müller et al, 2006 , Müller et al, 1998 ; Müller and Hillyard, 2000 ; Müller and Hübner, 2002 ; Steinhauser and Andersen, 2019 ; Toffanin et al, 2009 ; Walter et al, 2012 ).…”