Table 3. ROI correlation results for the two separate VBM analyses with Muller-Lyer and Ebbinghaus illusions, respectively.

Illusion used in VBM analysis	Identified cluster	Illusion used in ROI correlation analysis	Analysis results
Muller-Lyer	Right anterior PHC (MNI: 21, −7, −24)	Ebbinghaus	Rho = 0.356, p = 0.005, CI [0.00:0.64]
		Muller-Lyer	Rho = 0.460
		Ponzo	Rho = −0.127, p = 0.349, CI [−0.45:0.24]
		vertical-horizontal	Rho = 0.033, p = 0.808, CI [−0.33:0.37]
		contrast	Rho = 0.003, p = 0.986, CI [−0.33:0.33]
	Left posterior PHC (MNI: −27, −46, −8)	Ebbinghaus	Rho = 0.360, p = 0.002, CI [0.06:0.61]
		Muller-Lyer	Rho = 0.503
		Ponzo	Rho = −0.061, p = 0.662, CI [−0.41:0.29]
		vertical-horizontal	Rho = −0.085, p = 0.542, CI [−0.42:0.28]
		contrast	Rho = 0.085, p = 0.502, CI [−0.24:0.40]
Ebbinghaus	Right anterior PHC (MNI: 21, −10, −23)	Ebbinghaus	Rho = 0.423
		Muller-Lyer	Rho = 0.417, p = 0.001, CI [0.08:0.67]
		Ponzo	Rho = −0.118, p = 0.390, CI [−0.44:0.25]
		vertical-horizontal	Rho = 0.128, p = 0.345, CI [−0.22:0.45]
		contrast	Rho = −0.046, p = 0.726, CI [−0.38:0.30]
	Left posterior PHC (MNI: −30, −43, −12)	Ebbinghaus	Rho = 0.421
		Muller-Lyer	Rho = 0.451, p < 0.001, CI [0.16:0.67]
		Ponzo	Rho = −0.073, p = 0.613, CI [−0.44:0.30]
		vertical-horizontal	Rho = −0.078, p = 0.578, CI [−0.42:0.29]
		contrast	Rho = 0.086, p = 0.479, CI [−0.23:0.39]

The columns are: (1) the illusion used in VBM analysis for cluster identification; (2) the clusters identified in VBM analysis; (3) the illusion used for ROI correlation analysis and (4) the correlation analysis results. Note, that no statistical significance was determined when the same illusion was used for cluster identification and ROI analysis. Note the high correlations (marked with bold) for all clusters for Muller-Lyer and Ebbinghaus illusions. CI denotes 99% confidence intervals (accounting for multiple comparison correction, number illusions = 5).