Fig 1.
Examples of the stimuli used in the motion and spatial experiments.
(A-B) stimuli used in the motion experiment. (C-D) stimuli used in the spatial experiment. A) Gabor patch of 1 c/deg, 92% contrast, and a diameter of 0.7 deg (diameter = 2 × σxy). B) Gabor patch of 1 c/deg, 92% contrast, and a diameter of 6 deg. C) Example of the orthogonal surround condition. Target of 1 c/deg surrounded by a grating with the same spatial frequency; D) Example of the parallel surround condition. The contrast of the surround was fixed to 25%. On each trial, the target appeared randomly in one out of four possible positions.
Fig 2.
Results of motion and spatial experiments.
A) Duration thresholds (2 × σt) in logarithmic units (mean ± SEM) for each diameter tested (0.7 and 6 deg). B) Contrast thresholds (mean ± SEM) in logarithmic units for the orthogonal and parallel conditions. The horizontal line corresponds to the contrast thresholds (mean ± SEM) for the control condition without surround.
Fig 3.
Scatter plots of motion and spatial experiments.
A) Motion experiment results. Duration thresholds (in log values, mean ± SEM) for the large (Dlarge) stimulus (6 deg) as a function of the duration thresholds for the small (Dsmall) stimulus (0.7 deg). The red line shows the fitted regression line: Dlarge = 0.47 + 0.93 × Dsmall. B) Spatial experiment results. Contrast thresholds (in log values, mean ± SEM) for the parallel condition (Cparallel) as a function of the contrast thresholds for the orthogonal surround (Corthogonal). The red line shows the fitted regression line: Cparallel = 1.40 + 1.34 × Corthogonal. Pearson correlation (r) and p values are inserted in each panel. Dashed lines: 95% regression confidence interval.
Fig 4.
Relationship between Motion Suppression Index and IQ.
(A-C) Motion suppression index (MSI) as a function of IQ, for general (A), verbal (B), and non-verbal (C) intelligence. The red lines represent the fitted regression line. General intelligence: MSI = -0.48 + 0.008 × IQg; verbal intelligence: MSI = -0.26 + 0.006 × IQv; and non-verbal intelligence: MSI = -0.25 + 0.006 × IQn-v. (D-F) Duration thresholds (in log values, mean ± SEM) as a function of IQ, for general (D), verbal (E), and non-verbal (F) intelligence. Green squares, duration thresholds for the large stimulus (Dlarge); blue dots, duration thresholds for the small stimulus (Dsmall). Green lines, fitted regression lines for general intelligence: Dlarge = 1.24 + 0.007 × IQg; verbal intelligence: Dlarge = 1.32 + 0.006 × IQv; and non-verbal intelligence: Dlarge = 1.64 + 0.003 × IQn-v. Blue lines, fitted regression lines for general intelligence: Dsmall = 1.72–0.001 × IQg; verbal intelligence: Dsmall = 1.59–0.0001 × IQv; and non-verbal intelligence: Dsmall = 1.90–0.003 × IQn-v. Pearson correlation (r) and p values are inserted in each panel. Dashed lines: 95% regression confidence interval.
Fig 5.
Results from the spatial experiment.
Contrast suppression index (CSI) as a function of IQ for general (A), verbal (B), and non-verbal (C) intelligence. Red lines, fitted regression line for general intelligence: CSI = 0.95–0.002 × IQg; verbal intelligence: CSI = 0.70–0.0002 × IQv; and non-verbal intelligence: CSI = 1.31–0.005 × IQn-v. Pearson correlation (r) and p values are inserted in each panel. Dashed lines: 95% regression confidence interval.