Table 1.
Summaries of studies on the effect of red/blue colors on temporal perception (modified after Yang et al.).
Fig 1.
Experimental protocol for one trial.
(A) Depiction of one trial sequence in the experiment. Stim1 and Stim2 in the duration-discrimination task refer to either the reference interval (RI) or comparison interval (CI). In Experiment 2, the luminance of the color stimuli was adjusted based on PLR amplitude instead of subjective equiluminance. (B) Illustration of experimental conditions for the duration-discrimination task.
Fig 2.
Mean psychometric functions (subjective equiluminance).
Left panel: Psychometric function fitting by the proportion of comparison interval–longer (CI) response in congruent color sequence. Right: For an incongruent color sequence. Abbreviations: B–blue, R–red, CI–comparison interval, RI–reference interval.
Fig 3.
Mean PSE of each color sequence.
Violin plots of mean PSE as a function of stimulus sequence. The plots show the data distribution with a solid black line for the mean of the data. The overlaid semitransparent dot indicates the mean value for each participant’s data. * Indicates statistically significant (p < 0.05) differences in the analysis of variance and post-hoc testing. Abbreviations: B–blue, R–red, CI–comparison interval, PSE–point of subjective equality.
Fig 4.
Pupillary response to each color stimulus (subjective equiluminance).
(A) Mean change in pupil diameter from stimulus onset. Each line represents pupillary responses to RI and CI stimuli, whereas the shaded regions are standard errors of the mean. The x-axis range is limited to 1,600 ms, the shortest CI duration. (B) Mean peak PLR amplitude of each color condition. Peak PLR amplitude is determined as the minimum pupil diameter between 300–1,300 ms in the time domain. *** Indicates a statistically significant (p < 0.001) main effect by ANOVA. The semitransparent dots indicate each participant’s data. Abbreviations: ANOVA–analysis of variance, CI–comparison interval, PLR–pupillary light reflex, RI–reference interval.
Fig 5.
Example pupillary response and peak PLR amplitude.
(A) One participant’s mean pupillary response to different hues and luminances (color and luminance: two (color) × five (luminance) = ten combinations). Solid lines represent pupillary responses for each condition. (B) An example of mean peak PLR amplitude for each color condition. PLR diameter is computed as the minimum pupil diameter. The two dashed lines represent the fitted linear regression model, composed of discrete luminance and peak PLR amplitude data points, for red and blue stimuli, respectively. Abbreviations: PLR–pupillary light response.
Fig 6.
Pupillary response to each color stimulus (PLR-based equiluminance).
(A) Mean change in pupil diameter from stimulus onset. Each line represents pupillary responses to RI and CI stimuli, whereas the shaded regions are standard mean errors. (B) Mean peak PLR amplitudes for each color condition. Peak PLR amplitude is determined as the minimum pupil diameter between 300–1,300 ms in the time domain. The overlaid semitransparent dots indicate each participant’s data. Abbreviations: CI–comparison interval, PLR–pupillary light reflex, RI–reference interval.
Fig 7.
Mean psychometric functions (PLR-based equiluminance).
Left panel: Psychometric function fitting according to the proportion of comparison interval–longer (CI) responses in congruent color sequence. Right: For incongruent color sequence. Abbreviations: B–blue, R–red, CI–comparison interval, RI–reference interval.