The perceived directions of the dual barber poles in which the temporal frequency of the two component barber poles differed.

<p>A. Three example dual barber poles with the temporal frequency of left component barber pole 2/3 times (upper panel), equal (middle panel), or 3/2 times (lower panel) that of the right component barber pole. B–C. The probability the subject perceived a global percept observed in an example subject (B) and in the mean across subjects (C). D–E. The perceptual bias observed in an example subject (D) and in the mean across subjects (E). *: <i>p</i> < 0.05 across conditions.</p

The perceived directions of dual barber poles in which the phase of the two component barber poles differed.

<p>A. Three example dual barber poles in which the phase difference between the bilateral component barber poles was 0 (upper panel), 1/4 (middle panel), or 1/2 (lower panel) cycles. B–C. The probability of perceiving a global motion observed in an example subject (B) and in the mean across subjects (C). D–E. The perceptual bias observed in an example subject (D) and in the mean across subjects (E). *: <i>p</i> < 0.05 across conditions.</p

Examples of visual stimuli and illustrations of the filling-the-gap hypothesis.

<p>A–C. Single barber pole with aspect ratios (height: width) of (A) 1:1 (1.19°/1.19°), (B) 1:1.41 (1°/1.41°), and (C) 1.41:1 (1.41°/1°), and a fixed aperture area of 1.41 (°)². D–I. To test whether the perceived direction of the dual barber poles is mediated through the filling-the-gap hypothesis, we presented a series of completed barber poles (as shown in G, H, and I) constructed by filling the grating into the inter-component space of the dual barber poles in D, E, and F, respectively.</p

The perceived directions of the dual barber poles in which the two component barber poles had different temporal frequencies, but the same speed.

<p>A. Three example dual barber poles with the wavelength of the left component barber-pole 2/3 times (upper panel), equal (middle panel), or 3/2 times (lower panel) that of the right component barber pole. Their speed was fixed so that their temporal frequency ratio was inversely proportional to their wavelength ratio. B–C. The probability the subject perceived a global percept observed in an example subject (B) and in the mean across subjects (C). D–E. The perceptual bias observed in an example subject (D) and in the mean across subjects (E). *: <i>p</i> < 0.05 across conditions.</p

The perceived directions of single and dual barber poles and the predictions of the perceived directions of the dual barber poles based on the filling-the-gap and simple concatenation hypotheses.

<p>A. The mean perceptual bias toward the horizontal direction as a function of the aspect ratio induced by single barber poles illustrated in Figure 1A–C. The three barber poles with aspect ratios (height/width) of 1:1.41 (1°/1.41°), 1:1 (1.19°/1.19°), and 1.41:1 (1.41°/1°) are illustrated in the upper panel. The error bars indicate standard error of mean. B The mean perceptual bias toward the horizontal direction induced by the dual barber poles as a function of inter-component distance. Examples of the dual barber poles with inter-component distances of 0.03°, 0.41°, and 1.66° are illustrated in the upper panel. The perceptual bias to dual barber poles (circle trace) peaked when the inter-component distance was zero (yielding a single horizontal barber pole) and, as the inter-component distance increased, gradually decreased to approach the perceived direction of the single component barber pole. The dashed line indicates the perceptual bias induced by the single component barber pole (with an aspect ratio of 1.41:1) shown in (A). C–D. The perceptual bias to the dual barber poles at various inter-component distances (circle trace), the predictions made by the filling-the-gap (star trace) and simple concatenation hypotheses (dotted line), and the perceptual bias induced by the single component barber pole (dashed line), observed in an example subject (C) and in the mean across subjects (D) (* symbols indicate significant difference between the dual barber pole and completed barber pole, <i>p</i> < 0.05 using repeated-measures ANOVA).</p

The perceived directions of the dual barber poles in which the wavelength of the two component barber poles differed.

<p>A. Three examples of dual barber poles (inter-component distance = 0.21°) with the wavelength of the left component barber pole 2/3 times (upper panel), equal (middle panel), or 3/2 times (lower panel) that of the right component barber pole. The length of the arrows indicates the speed of the drifting grating. B–C. The probability the subject perceived a global percept instead of two individual component barber poles moving at different velocities observed in an example subject (B) and in the mean across subjects (C). The standard dual barber poles always elicited a global percept and the dual barber poles in which the wavelength differed in the component barber poles still tended to elicit a global percept. D–E. The perceptual bias observed in an example subject (D) and in the mean across subjects (E) decreased when the wavelength differed in the component barber poles and the inter-component distance was small (* symbols indicate the inter-component distance in which the perceptual bias differed among the three temporal frequency conditions, <i>p</i> < 0.05).</p

The perceived directions of the dual barber poles in which the contrast of the two component barber poles differed.

<p>A. Three example dual barber poles in which the contrast of the left component barber pole was 33% (upper panel), 50% (middle panel), or 75% (lower panel), and the right component barber pole was 75%. B–C. The probability of perceiving a global motion observed in an example subject (B) and in the mean across subjects (C) indicated that the dual barber poles in which the duty cycle differed in the component barber poles could still elicit a global percept. D–E. Surprisingly, the discrepancy in the contrast between the component barber poles did not alter the perceptual bias observed in an example subject (D) and in the mean across subjects (E) (<i>p</i> > 0.05 in all cross-condition comparisons).</p

The perceived directions of the dual barber poles in which the duty cycle of the two component barber poles differed.

<p>A. Three example dual barber poles with the duty cycle of the left component barber pole 2/3 times (upper panel), equal (middle panel), or 3/2 times (lower panel) that of the right component barber pole (duty cycle = 50%). B–C. The probability of perceiving a global motion observed in an example subject (B) and in the mean across subjects (C). D–E. The perceptual bias observed in an example subject (D) and in the mean across subjects (E). *: <i>p</i> < 0.05 across conditions.</p