Figure 1
Stimuli and luminance modulations used. Each row represents one presentation cycle (360° or 2π, corresponding to 0.588s at 1.7 Hz in steps of 30° (π/6)). In this example, the face image always represents the left and the house image the right eye. Note that the luminance modulation depicted here is only approximate depending on screen/printer calibration; in the actual experiment modulation was adjusted to be sinusoidal in luminance by correcting for display Gamma (γ = 2.26). Top: phase shift of 180° (π; counterphase). Middle: phase shift of 90° (π/2). Bottom: same phase (control).
Figure 2
Analysis of individual presentation cycles. Example data from one observer (luminance modulated condition at 180° phase difference; observer #3, block 2). Top: luminance modulation presented to the left (blue) and right eye (red). Middle: Raw z-standardized pupil trace. Colors indicate the percept reported by button press (blue: image in left eye, red: right eye). Bottom: F1 Fourier component of pupil signal at 1.7 Hz. Colors as in middle panel.
Table 1
Order of presentation conditions.
| Block | Condition name | Description (details see text) |
|---|---|---|
| 1 | initial static | house and face presented statically |
| 2–3 (counterbalanced) | 180° modulation (naïve) | face and house luminance-modulated in counterphase |
| 90° modulation (naïve) | face and house luminance-modulated with 90° phase shift, left eye leading | |
| 4 | 0° luminance-modulation control | both stimuli luminance-modulated in phase |
| 5–6 (counterbalanced) | 180° modulation (attention instruction) | face and house luminance-modulated in counterphase, instruction to attend either face or house alternating in 30s intervals |
| 90° modulation (attention instruction) | face and house luminance-modulated with 90° phase shift, left eye leading, instruction to attend either face or house, alternating in 30s intervals | |
| 7 | final static | house and face presented statically |
Figure 3
Pupillary response at 1.7 Hz (F1 component) over the duration of one presentation cycle, averaged over participants for all luminance modulation conditions and same phase control. Colors indicate reported percept (blue: left eye image, red: right eye image), shaded bands indicate +/–1 SEM.
Figure 4
Complex plane representation of F1 component, averaged across presentation cycles for each participant and luminance modulation condition. Blue circles indicate reported percept of left eye image, red circles report of right eye image. Lines connect opposing perceptual reports within each individual.