1. PERCEPTION OF THE FLASH-LAG EFFECT Maksims Ivanovs University of Tartu / University of Latvia Advisor: Jaan Aru

2. Introduction The flash-lag effect: http://www.michaelbach.de/ot/mot- flashLag/index.html Most likely caused by the neural delays in arrival of photoreceptor signals from retina to visual cortical areas Threshold: 1 rpm / 2 rpm Why it is important

3. The Present Research Purpose: to study possible effect of gender, age, education Hypotheses – Gender has an effect on the threshold – Age has an effect on the threshold – Education has an effect on the threshold Data gathering: a large-scale online survey

4. Survey The pilot study: 8 participants Design: – 3 parts: introduction, the questions regarding the perception of the visual stimulus, the questions regarding the participants himself / herself Two orders of the stimuli: – 10, 15, 5, 4, 3, 2, 1 rpm – 10, 5, 4, 3, 2, 1, 15 rpm Three languages: English, Latvian, Russian All in all – six versions

5. Administering the Survey Facebook, email Personal contacts Facebook groups: – ESN Tartu Spring 2014 – Neuroscience – Psychology Forwarding via email to the students: – UT Faculty of Mathematics and Computer Science – UT Faculty of Philosophy – UL Faculty of Humanities Key principles: – order of stimuli, gender, age, level of education

6. Raw Data N = 238 10, 15 … 1 rpm = 134 10, 5 … 15 rpm = 104 Gender: – Males: 63 – Females: 175 Age: group from 20-29 = 172 Education: – Secondary school = 88 – Bachelor degree = 80 Country of origin: 30 countries (Estonia, Latvia, Syria, Israel, Australia, etc.)

7. Preliminary Processing of the Data Invalid responses: – Don’t see any lines; – Inconsistent responses (5 rpm = Y, 4 rpm = N, 3 rpm = Y); – Not observing the effect at 15 rpm or 10 rpm Normalisation of the responses: – The questions regarding the respondent – The questions regarding the perception of the stimuli

8. Preliminary Processing of the Data Normalisation of the responses to the questions regarding the perception of the stimuli: – Normalised = 3 – Not normalised = 24 – ‘when vertical or horizontal, they [lines] appear aligned; when at 45 or 135 degrees, the flashing line appears to lag slightly’ – ‘[the flashing line (or the first line!?)] sometimes lags a little behind, sometimes [is] aligned and sometimes [runs] ahead’

9. Data N = 175 By gender: M = 51, F = 124

10. Data Age

11. Data Education

12. Average threshold = 2,594 rpm Bach = 1 rpm / 2 rpm

13. M = 2,35 F = 2,69 Wilcoxon rank sum test: p = 0.064 Not statistically significant, yet there is a trend

14. Spearman correlation test: rho = -.177, p < 0.025 Weak negative correlation

15. Kruskall Wallis test: p > 0.2 No effect

16. Conclusions Fairly large sample All respondents: 2,594 rpm vs 1 rpm / 2 rpm Gender: trend rather than effect Age: weak negative correlation Education: no effect Limitations of the research Further study: – Sample distribution by gender – Sample distribution by age

17. Thank you!