Pupillary response to moving stimuli of different speeds

Purpose: To investigate the pupillary response to moving stimuli of different speeds and the influence of different luminance environments. Methods: Twenty-eight participants with normal or corrected-to-normal vision were included. The participants were required to track moving optotypes horizontally, and their pupils were videoed with an infrared camera. Stimuli of different speeds were presented in different luminance environments. Results: Experiment 1 demonstrated that the motion stimuli induced pupil dilation in a speed-dependent pattern. The pupil dilation increased as the speed increased, and the pupil dilation gradually increased, then reached saturation. Experiment 2 showed that a stimulus targeting the rod- or cone-mediated pathway could induce pupil dilation in a similar speed-dependent pattern. The absolute but not relative pupil dilation in the cone paradigm was significantly larger than that in the rod paradigm. As the speed increased, the pupil dilation in the cone paradigm reached saturation at speed slower than the rod paradigm. Conclusions: Motion stimuli induced pupil dilation in a speed-dependent pattern, and as the motion speed increased, the pupil dilation gradually increased and reached saturation. And the speed required to reach saturation in the cone paradigm was slower than in the rod paradigm

The Eyes Have It: Sex and Sexual Orientation Differences in Pupil Dilation Patterns

Recent research suggests profound sex and sexual orientation differences in sexual response. These results, however, are based on measures of genital arousal, which have potential limitations such as volunteer bias and differential measures for the sexes. The present study introduces a measure less affected by these limitations. We assessed the pupil dilation of 325 men and women of various sexual orientations to male and female erotic stimuli. Results supported hypotheses. In general, self-reported sexual orientation corresponded with pupil dilation to men and women. Among men, substantial dilation to both sexes was most common in bisexual-identified men. In contrast, among women, substantial dilation to both sexes was most common in heterosexual-identified women. Possible reasons for these differences are discussed. Because the measure of pupil dilation is less invasive than previous measures of sexual response, it allows for studying diverse age and cultural populations, usually not included in sexuality research

Effect of pharmacological pupil dilation on measurements and iol power calculation made using the new swept-source optical coherence tomography-based optical biometer

Purpose: to determine whether pupil dilation affects biometric measurements and intraocular lens (IOL) power calculation made using the new swept-source optical coherence tomography-based optical biometer (IOLMaster 700©; Carl Zeiss Meditec, Jena, Germany). Procedures: eighty-one eyes of 81 patients evaluated for cataract surgery were prospectively examined using the IOLMaster 700© before and after pupil dilation with tropicamide 1%. The measurements made were: axial length (AL), central corneal thickness (CCT), aqueous chamber depth (ACD), lens thickness (LT), mean keratometry (MK), white-to-white distance (WTW) and pupil diameter (PD). Holladay II and SRK/T formulas were used to calculate IOL power. Agreement between measurement modes (with and without dilation) was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots. Results: mean patient age was 75.17 ± 7.54 years (range: 57–92). Of the variables determined, CCT, ACD, LT and WTW varied significantly according to pupil dilation. Excellent intraobserver correlation was observed between measurements made before and after pupil dilation. Mean IOL power calculation using the Holladay 2 and SRK/T formulas were unmodified by pupil dilation. Conclusions: the use of pupil dilation produces statistical yet not clinically significant differences in some IOLMaster 700© measurements. However, it does not affect mean IOL power calculation

Mental workload evaluation of pilots using pupil dilation

This study aims to propose a convenient method for evaluating human stress during high cognitive workload in hermetic space via monitoring changes in the eye pupil dilation. An experiment was carried out to establish the correlation between the changes in eye pupil dilation while operating human-machine system and both the pilot’s stress level and National Aeronautics and Space Administration Task Load Index (NASA-TLX). The experimental results indicate that detection accuracy of the flight operation task notably decreased and reaction time was prolonged when there was increased mental workload. At the same time, standard deviation of the recorded pupil dilation percentage significantly decreased. This highlights that the differences in eye pupil dilation can be used as reflective measure for mental workload level and performance assessment

N400 Amplitude Reduction Correlates with an Increase in Pupil Size

Pupil dilation is classically associated with increase in cognitive load in humans. Here, we studied the potential link between human pupil dilation and meaning integration effort as indexed by event-related brain potentials (ERPs). We recorded pupil size variation and ERPs simultaneously while participants were presented with matching or unrelated picture–word pairs. Whilst relatedness in meaning between spoken words and pictures typically modulated ERPs, pupil size was also affected quickly after picture onset. Moreover, during the time-window associated with meaning integration, greater pupil dilation correlated with less negative N400 amplitudes elicited by unrelated pictures. Since pupil dilation has been linked to activity of the locus coeruleus–norepinephrine (LC–NE) system, these findings may provide new insights into the suggested link between human high-level cognitive function and activity of the LC–NE system

Pupil Dilation is Not Associated with Memory for Prior Remembering

This experiment was conducted to assess the relationship between pupil dilation and memory for prior remembering. Prior remembering is the judgment of whether a memory was previously remembered. Previous studies have suggested that pupil dilation can change in response to emotional stimuli as well as “old” versus “new” stimuli in recognition memory tests. The present experiment had participants view emotional and neutral context image-word pairs before they completed two separate cued-recall tests. Critically, some image-word pairs changed between tests. During the second cued-recall test, participants were also asked to make a judgment about whether they previously retrieved a given word on the first test. It was found that pupil dilation was significantly greater for incorrectly remembered words compared to correctly remembered words during the first cued-recall test. No other hypotheses were supported, and pupil dilation did not differ whether participants were correct or incorrect about their judgment of prior remembering. Differences between the analyses that were run and stimuli presented in comparison with previous studies could have led to the null findings. These results suggested that a relationship may not exist between pupil dilation and memory for prior remembering

Fluctuation Patterns of Autonomic Arousal Predict Mental Arithmetic Performance

Pupil dilation, an autonomic arousal response, can measure attention because pupil dilation positively correlates with attention. This study investigated the predictability of mental arithmetic performance from pupil dilation fluctuation patterns of 11 college students. Arithmetic problems consisted of basic addition and varied in difficulty. The mental arithmetic task was administered while recording pupil dilation at 60 Hz with an ISCAN eye tracker. A pupil diameter baseline was measured before problems. Patterns of pupil diameter change from the baseline over time were analyzed by difficulty and performance. A marginal effect of Difficulty, marginal effect of Performance, and significant effect of Time on Pupil Dilation change were observed. Both Time by Difficulty and Time by Performance interacted significantly. However, Difficulty and Performance did not interact. These findings support the conclusion that attention increased over time during mental arithmetic problems. Furthermore, attention over time increased more on difficult problems and on correct problems

Pupil dilation reveals top–down attentional load during spatial monitoring

It has long been known that the diameter of human pupil enlarges with increasing effort during the execution of a task. This has been observed not only for purely mechanical effort but also for mental effort, as for example the computation of arithmetic problems with different levels of difficulty. Here we show that pupil dilation reflects changes in visuospatial awareness induced by attentional load during multi-tasking. In the single-task condition, participants had to report the position of lateralized, briefly presented, masked visual targets ("right", "left", or "both" sides). In the multitasking conditions, participants also performed additional tasks, either visual or auditory, to increase the attentional load. Sensory stimulation was kept constant across all conditions to rule out the influence of low-level factors. Results show that event-related pupil dilation strikingly increased with task demands, mirroring a concurrent decrease in visuospatial awareness. Importantly, pupil dilation significantly differed between two dual-task conditions that required to process the same number of stimuli but yielded differed levels of accuracy (difficulty). In contrast, pupil dilation did not differ between two conditions which were equally challenging but differed both in the modality of the dual task (auditory vs. visual) and in the number of stimuli to be attended. We conclude that pupil dilation genuinely reflects the top-down allocation of supramodal attentional resources

Truth and lies in your eyes: Pupil dilation of White participants in truthful and deceptive responses to White and Black partners

In the present study, we examined the pupillary response of White participants who were asked to tell the truth or lie to White or Black partners. Research on cues to deception has assumed that lying is more cognitively demanding that truth telling. In line with this assumption, previous studies have shown that lying is associated with greater pupil dilation, a behavioral cue that typically manifests itself under conditions of stress or cognitive effort. In accordance with these results, we predicted greater pupil dilation when lying than when telling the truth. Furthermore, pupil dilation was expected to be greater when responding to White than Black partners. Finally, we hypothesized that pupil dilation would be greater when lying to White than Black partners. Participants were instructed to answer a set of questions, half truthfully and half deceptively. They were led to believe that White vs. Black partners (one male and one female) would ask the questions via computer connection. Indeed, we used feminine and masculine synthetic voices. Pupil dilation was assessed with a remote eye-tracking system. Results provided support for the first two hypotheses. However, the predicted interaction between race of partners and truth status of message (lying vs. telling the truth) was nonsignificant. Our findings highlight the importance of considering race in the study of truthful and deceptive communications

Pupil Dilation to Explicit and Non-Explicit Sexual Stimuli

Pupil dilation to explicit sexual stimuli (footage of naked and aroused men or women) can elicit sex and sexual orientation differences in sexual response. If similar patterns were replicated with non-explicit sexual stimuli (footage of dressed men and women), then pupil dilation could be indicative of automatic sexual response in fully noninvasive designs. We examined this in 325 men and women with varied sexual orientations to determine whether dilation patterns to non-explicit sexual stimuli resembled those to explicit sexual stimuli depicting the same sex or other sex. Sexual orientation differences in pupil dilation to non-explicit sexual stimuli mirrored those to explicit sexual stimuli. However, the relationship of dilation to non-explicit sexual stimuli with dilation to corresponding explicit sexual stimuli was modest, and effect magnitudes were smaller with non-explicit sexual stimuli than explicit sexual stimuli. The prediction that sexual orientation differences in pupil dilation are larger in men than in women was confirmed with explicit sexual stimuli but not with non-explicit sexual stimuli