perception of the flash-lag effect - ut · the perception of the flash-lag effect is caused by the...

UNIVERSITY OF TARTU

FACULTY OF MATHEMATICS AND COMPUTER SCIENCE

INTRODUCTION TO COMPUTATIONAL NEUROSCIENCE

(MTAT.03.291)

PERCEPTION OF THE FLASH-LAG EFFECT RESEARCH PROJECT

Maksims Ivanovs

Student ID No B40200

Advisor: Jaan Aru

TARTU 2014

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Acknowledgements

I would like to express my sincere gratitude to my advisor Jaan Aru for his

supervision of my work on this project, his valuable advice and comments, and in

particular for his endless patience. His sense of humor was of great value as well, as it

made our cooperation truly enjoyable. I would also like to thank all the participants of

this study, because without their contribution it would not be possible to conduct it.

Finally, I would like to thank the administrative staff of the Faculty of Mathematics

and Computer Sciences and the Faculty of Philosophy of the University of Tartu and

the Faculty of Humanities of the University of Latvia for their assistance with

administering the survey.

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Contents

Introduction 4

Chapter 1 – Research Procedure 6

Chapter 2 - Design of the Survey and the Pilot Study 6

Chapter 3 – Administering the Survey 10

Chapter 4 - Description of the Raw Data and its Preliminary Processing 11

Chapter 5 - Analysis of the Data, Findings, and Interpretaion of Findings 13

Conclusions 20

References 21

Appendix 1 – Survey in English (10, 15 … 1 rpm order) 22

Appendix 2 – Survey in Latvian (10, 15 … 1 rpm order) 26

Appendix 3 – Survey in Russian (10, 5 … 15 rpm order) 30

Appendix 4 – Normalised Responses 35

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Introduction

The purpose of the present research is to study the perception of the visual

illusion known as the flash-lag effect. The said optical illusion can be best described

on the basis of its model available on the website of the notable researcher of visual

illusions Michael Bach (Figure 1; see also Online 1).

Figure Intro.1. Screenshot of a model of the flash-lag effect

The model consists of two blue lines rotating against the gray background; one

of the lines is visible all the time, while another line is flashing once in a while. As

Bach points out in his comments on the model (Online 1), these two lines may be

perceived in two different ways, namely, either they are perceived as aligned, i.e. the

flashing line as if continues another line without stopping, or the flashing line appears

to lag behind another line. In reality the two lines are always perfectly aligned, and

the perception of the flash-lag effect is caused by the pecularities of human visual

perception, which will be briefly outlined below. It should be pointed out that the

effect occurs when the lines rotate at a certain speed, but it disappears (i.e. the lines

are perceived as aligned) when the rotation speed is lowered to a certain threshold; in

Bach’s model it can be done by means of the menu next to the model. Thus, the effect

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is rather noticeable at the preset rotation speed, which is 10 rounds per minute (rpm)

and becomes even more conspicuous when the rotation speed is increased. However,

as Michael Bach observes, when the rotation speed is slowed down either to 2 or 1

rpm, by most of the observers the lines are perceived as aligned (Online 1). It is worth

noticing that the above Michael Bach’s comments on the model imply that for

different people the threshold at which the illusion disappears is different, i.e. there is

not just one set threshold value for all the observers.

As it has already been mentioned, the flash-lag effect is caused by certain

pecularities of visual perception. As Nijhawan points out (2002: 387), most of the

researchers that have studied the effect argue that this visual illusion is most likely

caused by neural delays in arrival of photoreceptor signals from retina to visual

cortical areas. However, as more detailed explanations of the nature of the neural

processes underlying the flash-lag effect provided by different authors are rather

dissimilar ( see ibid.: 387-391), it is necessary to study the effect in a greater detail.

The flash-lag effect has been previously studied by Bachman and Põder (2001) and

by Nijhawan (2002). However, according to the information available to the author of

the present paper, it appears that there has not been a large-scale study aiming at

investigating of whether the perception of the flash-lag effect is affected by gender,

age, or other similar characteristics of observers. The study of the effect of these

predictors would possibly allow to gain an insight into the neural processes

underlying the flash-lag effect. Therefore, the purpose of the present research was to

study the effect of the age, gender, and level of education of respondents on the

perception of the flash-lag effect. The following hypotheses were proposed:

• Gender of the respondents has an effect on the threshold at which the

illusion disappears;

• Age of the respondents has an effect on the threshold at which the

illusion disappears;

• Education of the respondents has an effect on the threshold at which

the illusion disappears;

Taking into account that such study would require quite large number of

participants, the study was conducted in the form of an online survey.

The present paper consists of five chapters. Chapter 1 describes the

research procedure. Chapter 2 is dedicated to the design of the survey and the pilot

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study. Chapter 3 deals with administering the survey. Chapter 4 comprises the raw

data and their preliminary processing. Chapter 5 is dedicated to the analysis of data,

findings, and interpretation of findings.

CHAPTER 1 – RESEARCH PROCEDURE

Chapter 1 describes the research procedure of the present study. The research

procedure consisted of the following steps:

• First, the initial version of the survey was designed, the pilot study was

conducted, and the final version of the survey was designed. The purpose of

the pilot study was to investigate whether the questions of the survey would be

comprehensible for the participants and to obtain the suggestions of the

participants of the pilot study as to how the design of the survey could be

improved;

• Second, the survey was administered to as large number and as diverse range

of participants as possible by means of sharing links to it via Facebook and

email;

• Third, the obtained data were processed preliminary in order to exclude

invalid responses and to prepare the data for statistical analysis;

• Finally, the data were analysed and the findings of the research were

formulated and interpreted.

CHAPTER 2 – DESIGN OF THE SURVEY AND THE PILOT

STUDY

Chapter 2 deals with the design of the survey and the pilot study. The design

of the survey was based on two key considerations. On the one hand, it was necessary

to obtain from the respondents the amount of information that would be sufficient to

test the hypotheses. On the other hand, taking into account that as a rule respondents

are rather reluctant to dedicate too much time to taking a survey, it was necessary to

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make the survey as short and comprehensible as possible. In order to satisfy the

former consideration, the survey included the questions regarding the perception of

the flash-lag effect with different rotation speed of the lines as well as questions about

the gender, age, level of education, and country of origin of respondents. In order to

satisfy the latter consideration, the questions were carefully worded to exclude

ambiguity as well as most of the questions were multiple choice questions rather than

open-ended questions.

The survey was hosted on the Google Docs platform. The initial version of the

survey consisted of three parts, namely, the introductory part, the part with the

questions regarding the perception of the flash-lag illusion, and the part with the

questions regarding the participant himself or herself.

The introductory part briefly introduced the purpose of the research to the

respondenta, provided them with the instructions on how to take the survey, included

the contact information (email address) of the research in case there should be any

difficulties with taking the survey, and provided a link to the visual stimulus used in

the research. The said visual stimulus was a modified version of the flash-lag effect

available on Michael Bach’s website (Online 1). The essence of modification was that

Bach’s description of the model and comments on the model were made invisible,

that is, when opening the link to the stimulus the respondent would see only the

model itself and the menu next to it. The purpose of the modification was to avoid

possible influence of the description of the effect and in particular comments on it on

the responses of the respondents.

The second part consisted of the questions regarding perception of the visual

stimulus. The respondent had to have two tabs or windows of the Internet browser

opened: the first one with the survey itself and the second one with the visual

stimulus. The questions asked the respondent to report how he or she perceived the

visual stimulus. The respondent was provided with three response options: either the

flashing line appeared to lag behind the other line, or the both lines were aligned, or,

if the respondent was not satisfied with these response options, he or she could choose

the option ‘other’ and provide his or her own response. As to the visual stimuli, for

the first time the visual stimulus was presented with the preset rotation speed of the

lines of 10 rpm, but when responding to the following questions the respondent was

asked to change the rotation speed of the lines himself or herself, using the menu to

the right of the stimulus.

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The third part of the survey consisted of the questions about the respondent

himself or herself. Namely, the respondent was asked to provide information about

his or her gender, age, level of education, and country of origin. When the questions

were answered and the survey was completed, the respondent would receive a

notification on the screen informing him or her that that the responses had been saved

and thanking him or her for the participation.

When the initial version of the survey was designed, the pilot study was

conducted. The pilot study included 8 respondents: 4 males and 4 females from

Latvia, Estonia, and Germany, with age ranging from 22 to 31 and level of completed

education ranging from secondary school up to master’s degree (see the file

Pilot_data.xlsx). In addition to taking the survey, they were asked to give some

feedback on the design and comprehensibility of the survey. In general they reported

that taking the survey did not cause any particular difficulty for them; however, their

feedback also resulted in some changes in the design of the survey. Apart from minor

changes, such as correction of spelling slips and improved wording of the

instructions, some more significant changes were introduced as well. First, the survey

was supplemented with the illustration of how the rotation speed of the lines could be

changed. The illustration was added to the second question regarding the perception

of the visual stimulus, because when answering that question the respondent would

have to change the rotation speed of the stimulus for the first time and could

experience some difficulty with finding the proper option in the menu next to the

stimulus. Second, the survey was supplemented with one more question regarding the

perception of the visual stimulus. Namely, the initial survey included questions

regarding the perception of the stimuli at the rotation speed of the lines of 10 rpm, 15

rpm, 5 rpm, 4 rpm, 2 rpm, and 1 rpm, while the final version of the survey in addition

to the above questions also included the question about the perception of the stimulus

at 3 rpm, which by accident was omitted from the initial version.

As in can be seen from the above description of the changes in the design of

the survey, although these changes were quite significant and essential for the purpose

of the research, in general they consisted of the corrections of mistakes and omissions

made in the initial version of the survey rather than presented radical changes in

comparison with the initial version. In addition to these changes, there were also more

significant improvements in the design of the survey related to the question regarding

the perception of the visual stimulus and the language of the survey. As to questions

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regarding the perception of the visual stimulus, it has already been mentioned that

after the addition of the omitted question the survey included questions regarding the

perception of the flash-lag effect with the rotation speed of the lines of 10 rpm, 15

rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, and 1 rpm. However, it was assumed that having

just one order of the stimuli would not produce enough variation; therefore, in

addition to the version of the survey with the above order of changes in the rotation

speed of the lines another version of the survey was designed with the order of

changes of 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, and 15 rpm. As it can be seen,

the stimulus with the highest rotation speed, 15 rpm, was moved from the second

position in the order to the last position. As to the language of the survey, it was

decided to design separate versions of the survey in three languages, namely, in

English, Latvian, and Russian, as it was obvious that it for a participant it would be

easier and less time-consuming to take the survey in his or her native tongue or at

least in the foreign language he or she is quite familiar with. Therefore, introduction

of several versions of the survey in different languages would make it more likely that

the respondents would be willing to participate in the survey and would avoid

mistakes caused by misunderstanding the questions. The choice of the above three

languages was determined by the supposed range of the participants as well as the by

the linguistic competence of the author of the present research.

Taking into account the introduction of two different orders of the rotation speed

of the lines and three languages, all in all the survey included of the six versions:

• Version in English with 10 rpm, 15 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, and 1

rpm order;

• Version in Latvian with 10 rpm, 15 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, and 1

rpm order;

• Version in Russian with 10 rpm, 15 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, and 1

rpm order;

• Version in English with 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, and 15

rpm order;

• Version in Latvian with 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, and 15

rpm order;

• Version in Russian with 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, and 15

rpm order.

10

The English version with 10, 15 … 1 rpm order, the Latvian version with 10, 15…

1 rpm order, and the Russian version with 10, 5, … 15 rpm order are accordingly

available in Appendix 1, Appendix 2, and Appendix 3.

CHAPTER 3 – ADMINISTERING THE SURVEY

Chapter 3 is devoted to the description of administering the survey. Taking

into account that it was necessary to involve a large number of participants, the

respondents were invited to take part in the survey by means of the use of electronic

means communication, namely, social network Facebook and email. Potential

respondents were addressed in several different ways. First, the author of the research

sent messages and emails with a link to one of the survey version to potential

respondents on Facebook and via email. The language of the message and of the

version of the survey were fitted to the language of a potential respondents. Second,

the author posted brief information about the survey, links to it and invitations to

participate in it in various Facebook groups, such as ESN Tartu Spring 2014 (Online

2), Psychology (Online 3), and Neuroscience (Online 4). The language of the posts

and surveys was English, as it was assumed that it is the lingua franca of social

networks. Third, invitations to participate in the survey and links to it were forwarded

to the students of Faculty of Philosophy and the Faculty of Mathematics and IT of the

University of Tartu and the Faculty of Humanities of the University of Latvia by

means of intermediacy and thanks to the kind help of the administrative staff of these

academic establishments. Observing the principle of trying to fit the language of the

invitation and the language of the survey to potential respondents, the Estonian

audience was addressed in English, while the Latvian audience was addresses in

Latvian.

Another essential principle of administering the survey was that it was

attempted to achieve as high representativeness of the population as possible, namely:

• To involve approximately the same number of male and female participants;

• To involve as broad range of participants in regard to their age as possible;

• To involve as broad range of participants in regard to their level of education

as possible.

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Finally, it was attempted to involve approximately the same number of

participants for the three versions of the survey with the order of change in the

rotation speed of the lines 10 rpm, 15 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, and 1 rpm as

for the three surveys with the order 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, and

15 rpm. In order to achieve that goal, the total number of responses for each order of

was monitored and in case of discrepancy the links to the surveys which currently

had smaller number of participants were shared more intensively than their more

successful counterparts.

CHAPTER 4 – DESCRIPTION OF THE RAW DATA AND ITS

PRELIMINARY PROCESSING

Chapter 4 is dedicated to the description of the raw data and its preliminary

processing. The raw data were as follows:

• The overall number of respondents: 238

• The number of the respondents for the version of the survey with the order 10

rpm, 15 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm: 134

• The number of the respondents for the version of the survey with the order of

stimuli 10 rpm, 5 rpm, 4 rpm, 3 rpm, 2 rpm, 1 rpm, 15 rpm: 104

• Male respondents: 63

• Female respondents: 175

• Respondents by age:

o up to 19 years of age: 15

o 20-29 years of age: 172


o > 40 years of age: 18

• Respondents by level of education:

o Less than secondary school: 1

o Secondary school: 88

o Bachelor degree or equivalent: 80

o Master’s degree or equivalent: 52

o Doctoral degree or equivalent: 13

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o Other: 4

• Number of the different countries of origin: 30

The raw data is available in the file Raw_data.xlsx.

In order to proceed with the statistical analysis of the data, the raw data were

preliminary processed. The preliminary processing of the data consisted of the

following stages:

• First, the several respondents who reported not seeing any lines on the

screen or not understanding the instructions were removed from the data,

as their responses were obviously invalid;

• Second, the respondents who provided inconsistent responses were

removed from the data. The term ‘inconsistent response’ stands for the

cases when the respondent reported the disappearance of the effect at a

certain rotation speed (e.g. 5 rpm) and then reported observing it again at a

lower speed (e.g. 2 rpm). The reason for the removal of such responses

was that the flash-lag effect becomes more noticeable as the rotation speed

increases; therefore, it is likely that such respondents were inattentive, or

by mistake chose the wrong response option, or just chose the response

option at random;

• Third, as the subsequent statistical analysis of the data would require

coding of the responses to the questions regarding the perception of visual

stimulus in the form or ‘yes’ or ‘no’ responses, the cases when the

respondents responded to such question by means of choosing the

response option ‘other’ were investigated. The purpose of the investigation

was to normalise the ‘other’ responses to ‘yes’ / ‘no’ responses or, when it

was impossible, to remove respondents who provided such responses from

the data. All in all 27 cases were investigated; in three cases it was

possible to normalise the ‘other’ responses, while in 24 cases it was

necessary to remove the respondent from the data. The table with the

normalised responses is available in Appendix 4. It should be pointed out

that in some case when the respondent had to be removed from the data

the ‘other’ responses were quite interesting. Thus, one of the respondents

reported that at the rotation speed 5 rpm she observed that ‘when vertical

or horizontal, they [lines] appear aligned; when at 45 or 135 degrees, the

13

flashing line appears to lag slightly’. Another respondent reported that

‘Where the two lines meet they appear aligned, however, the flashing line

seems to be angled in a way that makes it appear lagging’. Yet another

respondent reported that ‘[the flashing line (or the first line!?)] sometimes

lags a little behind, sometimes [is] aligned and sometimes [runs] ahead’.

• Fourth, the respondents who reported not observing the flash-lag effect at

15 rpm or 10 rpm, as it was rather improbable that the threshold were so

high.

• Fifth, the responses ‘other’ to the questions regarding the level of

education and the country of origin of the participants were normalised.

The normalisation did not cause any significant difficulty. For instance,

the response of one of the participants to the question regarding the level

of education ‘1st year of PhD’ was normalised to the response ‘Master’s

degree or equivalent’; the response of another participant to the question

regarding the country of origin ‘Eesti’ was normalised to the response

‘Estonia’.

• Finally, all the data were put in one data sheet and the threshold was

determined of each of the respondents. As it has already been mentioned,

the threshold is defined as the rotation speed rotation of the lines at which

the respondent reports not observing the flash-lag effect. Thus, for the

respondent who observes the effect at 10 rpm, 15 rpm, 5 rpm, 4 rpm, and 3

rpm, but reports not seeing it at 2 rpm and 1 rpm the threshold is 2 rpm.

CHAPTER 5 – ANALYSIS OF THE DATA, FINDINGS, AND THE

INTERPRETATION OF THE FINDINGS

Chapter 5 is dedicated to the analysis of the data, description of the findings of

the present research, and the interpretation of the findings. The data that were

considered valid for the further analysis after the preliminary processing are available

in the file All_data.xlsx and were as follows:

• The overall number of the respondents: 175

• Respondents by gender:

14

o Males: 51

o Females: 124

Figure 5.1. Respondents by gender

• Respondents by age:

o Up to 19 years of age: 14



o > 40 years of age: 10

Figure 5.2. Respondents by age

0

20

40

60

80

100

120

140

N of respondents by gender

Males

Females

0

20

40

60

80

100

120

140

N of respondents by age

Up to 19

20-‐29

30-‐39

> 40

15

• Respondents by level of education:

o Secondary school: 72

o Bachelor degree or equivalent: 59

o Master’s degree or equivalent: 36

o Doctoral degree or equivalent: 8

Figure 5.3 Respondents by level of education

As it can be seen, the overall number of the respondents is fairly large and may

considered to be quite sufficient for the purpose of the present research. However, it

should be observed that the distribution of the respondents by gender and by age is far

from desired. Namely, as to the distribution by gender, there is a significant

predominance of female respondents over male respondents; as to the distribution by

age, the group of the respondents aged from 20 to 29 is unproportionally large

compared with other age groups. In addition, it should be mentioned that there were

not respondents younger than 18 or older that 50. The distribution of the respondents

by level of education again demonstrates discrepancies, as the number of the

respondents on earlier stages of their education is larger than the number of

participants on later stages of their education. The above discrepancies regarding the

distribution of the participants by gender, age, and level of education should be

considered as the limitations of the present research.

The first step of the statistical analysis of the data was to calculate the average

threshold and the standard deviation for all participants. The corresponding values are

provided below in Table 5.1.

0

10

20

30

40

50

60

70

80

N of respondents by education

Secondary School

Bachelor degree

Master's degree

PhD

16

Table 5.1. The average threshold and standard deviation for all respondents

Measurement Value

Average Threshold 2,594285714

Standard Deviation 1,755441926

Figure 5.4. The average threshold and standard deviation for all respondents

As it can be seen, the average threshold for all respondents is somewhat higher

than the average threshold reported by Bach, according to whom the flash-lag effect

disappears for most observers at 1 or 2 rpm.

The second step of the statistical analysis of the data was to calculate the

average threshold and the standard deviation by gender. The corresponding values are

provided below in Table 5.2.

Table 5.2. The average threshod and standard deviation by gender.

Gender Average Threshold Standard Deviation

Male 2,352941176 1,683134331

Female 2,693548387 1,781464727

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

1

Average threshold for all respondents

Average threshold for all respondents

17

Figure 5.5. The average threshod and standard deviation by gender.

In addition, in order to determine whether the predictor ‘gender’ has any

statistically significant effect on the threshold the Wilcoxon rank sum test was used.

The test yielded the result p = 0.064. Therefore, although strictly speaking the

predictor ‘gender’ cannot be considered to have a statistically significant effect on the

average threshold, there is a certain trend observed.

The third step of the statistical analysis of the data was to calculate the average

threshold and the standard deviation by age. The corresponding values are provided

below in Table 5.3.

Table 5.3. The average threshold and standard deviation by age

Age Average Threshold Standard Deviation

0-19 3,142857143 1,703261255

20-29 2,637096774 1,773035051

30-39 2,222222222 1,804552647

> 40 2,3 1,418136492

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Male Female

Average threshold by gender

Average Threshold

18

Figure 5.6. The average threshold and standard deviation by age

Figure 5.7. Scatter plot for the average threshold by age

In addition, in order to determine whether the predictor ‘age’ has any effect on

the threshold, the Spearman correlation test was applied. The test yielded the results

rho = -.177, p < 0.025. Therefore, there is a weak negative correlation between the

predictor ‘age’ and the average threshold.

0

1

2

3

4

5

6

0-‐19 20-‐29 30-‐39 > 40

Average threshold by age

Average Threshold

0

1

2

3

4

5

6

0 10 20 30 40 50 60

Average Threshold by Age

Average Threshold by Age

19

The fourth step of the statistical analysis of the data was to calculate the

average threshold and the standard deviation by level of education. The corresponding

values are provided in Table 5.4.

Table 5.4. The average threshold and standard deviation by education

Education Average Threshold Standard Deviation

SS 2,722222222 1,745999227

BA 2,694915254 1,868562395

MA 2,333333333 1,690308509

PHD 1,875 1,125991626

Figure 5.8. The average threshold and standard deviation by education

In addition, Kruskall Wallis test was applied to the data in order to investigate

whether the predictor ‘education’ has any statistically significant effect on the average

threshold. As the test yielded p > 0.2, it may be concluded that the predictor

‘education’ does not exert any statistically significant influence on the average

threshold.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

SS BA MA PHD

Average threshold by education

Average Threshold

20

CONCLUSIONS

The purpose of the present research was to investigate the perception of the

flash-lag effect. In the course of the research three hypotheses were tested, namely,

the hypothesis that the gender of an observer has an effect on the threshold at which

the effect disappears, the hypothesis that the age of an observer has an effect on the

threshold at which the effect disappears, and the hypothesis that the education of an

observer has an effect on the threshold at which the effect disappears. The data was

gathered by means of conducting a large-scale online survey. The initial number of

the respondents was 238, the number of responded whose responses were considered

valid after the preliminary processing of the data was 175. The average threshold for

all respondents was 2,594, which is slightly higher than than the average threshold

reported by Bach, according to whom the flash-lag effect disappears for most

observers at 1 or 2 rpm. The statistical analysis of the data did not confirm that the

predictor ‘education’ has any statistically significant effect on the average threshold.

It was discovered that there was a slight negative correlation between the predictor

‘age’ and the average threshold; although the p-value for the predictor ‘gender’

exceeds the threshold of 0.05 (p = 0.064) and therefore strictly speaking cannot be

considered statistically significant, there is still a trend present indicating the possible

influence of this predictor on the average threshold. Taking into account that males

and the age groups other than respondents from 20 to 29 years of age were rather

underrepresented in the study, large-scale research involving equal proportions of

participants of both genders and with better representation of all age groups is

required in order to investigate the possible effect of gender and age of observers on

the average threshold.

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References: 1. Nijhawan, R. (2002) Neural delays, visual motion and the

flash-lag effect. In TRENDS in Cognitive Sciences Vol.6 No.9 September 2002, Pages

387-393

2. Bachmann, T., Põder, E. (2001) Change in feature space is not necessary for

the flash-lag effect. In Vision Research. Volume 41, Issue 9, April 2001, Pages

1103-1106

Online sources: 1. Online Source 1. Flash-lag effect http://www.michaelbach.de/ot/mot-

flashLag/index.html

2. Online Source 2. Facebook group ESN Tartu Spring 2014

https://www.facebook.com/groups/458756300902163/

3. Online Source 3. Facebook group Psychology

https://www.facebook.com/pages/Psychology/57848692847?fref=ts\

4. Online Source 4. Facebook group Neuroscience

https://www.facebook.com/Neuroscience.LabRootsPage

22

Appendix 1

Survey in English (10, 15, 5, 4, 3, 2, 1 rpm order)

Page 1

Research on Visual Perception

Maksims Ivanovs, University of Latvia / University of Tartu

[email protected]

Dear participant,

Thank you very much for your willingness to contribute to the research. The purpose

of the research is to study some peculiarities of visual perception. The questionnaire

will not take more than 3 minutes for you to answer, as the questions are very simple.

Yet please consider the following instructions before you proceed with the questions:

1. When answering the questions, please concentrate on them. Do NOT talk to other

people, or read anything, or browse the Web at the same time.

2. Please answer ALL the questions, including those about your age, gender,

education, and the country of origin. The questionnaire is anonymous, yet the above

information about the participants is very important for the purpose of the present

research.

3. If you experience any problems with the questionnaire or would like to ask any

questions about the research, do not hesitate to contact me at

mailto:[email protected]

4. Now please open the link http://michaelbach.de/ot/mot-flashLag/capp/index.html in

a new tab or a new window. It is a link to the visual stimulus that will be used in the

research.

Do NOT close the tab/the window with the questionnaire.

Page 2

Question 1

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Now you see the moving blue line, and the second blue line flashing once in a while.

Please report what you see:

• the moving blue line and the flashing blue line are aligned

• where the two lines nearly meet, the flashing line appears to lag a little behind

the other line

• Other:

Page 3

Question 2

Please change the speed of the rotation of the lines to 15 rpm. You can do that by

using the menu to the right of the figure (the small window with “rpm” written next to

it; the red arrow is pointing at in the illustration below). Please report what you see.



the other line

• Other:

24

Page 4

Question 3

Please change the speed of the rotation of the lines to 5 rpm. Please report what you

see.



the other line

• Other:

Page 5

Question 4


see.



the other line

• Other:

Page 6

Question 5


see.



the other line

• Other:

Page 7

Question 6


see.


25


the other line

• Other:

Page 8

Question 7


see.



the other line

• Other:

Page 9

Gender

What is your gender?

• male

• female

Age

What is your age?

Education

What is the highest level of education you have completed?

• Less than secondary school

• Secondary school

• Bachelor's degree or equivalent

• Master's degree or equivalent

• Doctoral degree or equivalent

Country of origin

What is your country of origin?

26

Page 10 / Confirmation page

Thank you very much for your contribution! Your response has been recorded.

Appendix 2

Survey in Latvian (10, 15, 5, 4, 3, 2, 1 rpm order)

Page 1

Pētījums par vizuālo uztveri

Maksims Ivanovs, Latvijas Universitāte / Tartu Universitāte

[email protected]

Cienījamais / cienījamā pētījuma dalībniek / dalībniece,

Paldies par Jūsu gatavību piedalīties pētījumā! Šī pētījuma mērķis ir izpētīt dažas

vizuālās uztveres īpatnības. Aptaujas aizpildīšana prasīs ne vairāk kā 3 minūtes, jo tās

jautājumi ir ļoti vienkārši. Tomēr pirms atbildat uz tiem, lūdzu, uzmanīgi izlasiet

sekojošas instrukcijas:

1. Atbildot uz jautājumiem, lūdzu, koncentrējieties uz tiem! Lūdzu, nerunājiet ar

citiem cilvēkiem un nenovērsiet Jūsu uzmanību uz citu materiālu lasīšanu vai citu

Interneta mājas lapu skatīšanos šīs aptaujas aizpildīšanas laikā!

2. Lūdzu, atbildiet uz VISIEM jautājumiem, ieskaitot jautājumus par Jūsu vecumu,

dzimumu, izglītību un izcelsmes valsti! Aptauja ir anonīma, bet šī informācija par

aptaujas dalībniekiem ir ļoti svarīga priekš šī pētījuma.

3. Ja Jums rodas kādas problēmas ar aptaujas aizpildīšanu vai ir kādi jautājumi par šo

pētījumu, lūdzu, sazinieties ar mani, rakstot uz epastu

[email protected]

4. Tagad, lūdzu, atveriet saiti http://michaelbach.de/ot/mot-flashLag/capp/index.html

Interneta pārlūkprogrammas jaunajā logā vai cilnē. Jūs ieraudzīsiet vizuālo stimulu,

27

kas tiks izmantots šajā aptaujā. Lūdzu, neaizveriet Interneta pārlūkprogrammas logu

vai cilni ar aptauju!

Page 2

1. jautājums

Tagad uz ekrāna Jūs redzat kustīgu zilu līniju, ka arī otru līniju, kura ik pēc laika

mirgo. Kā Jūs redzat šīs līnijas? Lūdzu, izvēlieties vienu no atbildes variantiem.

Piezīme: “other” nozīmē “cita atbilde”.

• Kustīgā zilā līnija un mirgojošā zilā līnija ir izlīdzinātas attiecībā viena

pret otru

• Tur, kur divas līnijas gandrīz satiekas, mirgojošā līnija mazliet atpaliek no

otras līnijas

• Other:

Page 3

2. jautājums

Lūdzu, nomainiet līniju griešanās ātrumu uz 15 apgriezieniem minūtē. Lai to izdarītu,

izmantojiet izvēlni pa labi no vizuālā stimula, proti, lodziņu ar uzrakstu “rpm”.

Ilustrācijā uz to norāda sarkana bulta. 1 rpm = 1 apgrieziens minūtē. Ko Jūs redzat

tagad?

• Kustīgā zilā līnija un mirgojošā zilā līnija ir izlīdzinātas attiecībā viena pret

otru


otras līnijas

• Other:

28

Page 4

3. jautājums

Lūdzu, nomainiet līniju griešanās ātrumu uz 5 apgriezieniem minūtē. Ko Jūs redzat

tagad?


otru


otras līnijas

• Other

Page 5

4. jautājums


tagad?


otru.


otras līnijas

• Other:

Page 6

5. jautājums


tagad?


otru


otras līnijas

• Other:

Page 7

6. jautājums

29


tagad?


otru


otras līnijas

• Other:

Page 8

7. jautājums

Lūdzu, nomainiet līniju griešanās ātrumu uz 1 apgriezienu minūtē. Ko Jūs redzat

tagad?


otru


otras līnijas

• Other:

Page 9

Dzimums

Lūdzu, norādiet Jūsu dzimumu!

• vīriešu

• sieviešu

Vecums

Lūdzu, norādiet Jūsu vecumu!

Izglītība

Lūdzu, norādiet augstāko izglītības līmeni, kuru Jūs esat pabeidzis/pabeigusi!

• Nepabeigta vidusskolas izglītība

• Vidusskolas izglītība

• Bakalaura grāds vai tam pielīdzināms grāds

• Maģistra grāds vai tam pielīdzināms grāds

30

• Doktora grāds vai tam pielīdzināms grāds

• Other:


Paldies par Jūsu piedalīšanos pētījumā! Jūsu atbildes uz aptaujas jautājumiem tika

saglābātas!

Appendix 3

Survey in Russian (10, 5, 4, 3, 2, 1, 15 rpm order)

Page 1

Исследование зрительного восприятия

Максим Иванов, Латвийский университет / Тартуский университет

[email protected]

Уважаемый/ уважаемая участник/-ца исследования,

Прежде всего, спасибо за Ваше согласие участвовать в исследовании! Целью

данного исследования является изучение некоторых особенностей зрительного

восприятия. Так как вопросы в анкете, на которую Вам предстоит ответить,

очень простые, Вам потребуется не более 3 минут на ее заполнение. Тем не

менее, перед тем, как Вы начнете отвечать на вопросы, пожалуйста

ознакомьтесь со следующими инструкциями:

1. Отвечая на вопросы, пожалуйста сосредоточьтесь на них. Не говорите с

другими людьми, не отвлекайтесь на чтение или просмотр других интернет-

страниц во время заполнения анкеты.

2. Пожалуйста, ответьте на ВСЕ вопросы в анкете, включая вопросы о Вашем

возрасте, половой принадлежности, образовании и стране происхождения.

Результаты анкетирования анонимны, но вышеуказанная информация очень

важна для данного исследования.

31

3. Если у Вас возникли какие-либо проблемы при заполнении анкеты или же у

Вас имеются какие-либо вопросы о данном исследовании, пожалуйста

свяжитесь со мной с помощью электронной почты. Мой адрес электронной

почты - mailto:[email protected]

4. Теперь пожалуйста откройте ссылку http://michaelbach.de/ot/mot-

flashLag/capp/index.html в новой вкладке или новом окне Интернет-браузера.

Эта ссылка приведет Вас на страницу с визуальным стимулом, который будет

использоваться в данном исследовании. Пожалуйста, НЕ ЗАКРЫВАЙТЕ

вкладку или окно Интернет-браузера, в котором у Вас открыта данная анкета!

Page 2

Первый вопрос

На экране Вы видите движущуюся синюю линию, а также вторую линию,

которая время от времени мигает. Какими Вы видите эти линии? Выберите

один из вариантов ответа. Примечание: "other" означает "другой вариант

ответа"

• движущаяся синяя линия и мигающая линия выровнены относительно

друг друга

• там, где две линии почти встречаются, мигающая линия немного отстает

от другой линии

• Other:

Page 3

Второй вопрос

Пожалуйста, установите скорость вращения линий на 5 оборотов в минуту. Вы

можете это сделать, используя меню справа от визуального стимула - окошко,

рядом с которым написано "rpm". На изображении внизу на это окошко

указывает красная стрелка. 1 rpm = 1 оборот в минуту. Что Вы видите теперь?


друг друга

32



• Other:

Page 4

Третий вопрос

Пожалуйста, установите скорость вращения линий на 4 оборота в минуту. Что

Вы видите теперь?


друг друга



• Other:

Page 5

Четвертый вопрос



33


друг друга



• Other:

Page 6

Пятый вопрос




друг друга



• Other:

Page 7

Шестой вопрос

Пожалуйста, установите скорость вращения линий на 1 оборот в минуту. Что



друг друга



• Other:

Page 8

Седьмой вопрос

Пожалуйста, установите скорость вращения линий на 15 оборотов в минуту.

Что Вы видите теперь?


друг друга

34



• Other:

Page 9

Пол

Пожалуйста, укажите Ваш пол:

• мужской

• женский

Возраст

Пожалуйста, укажите Ваш возраст:

Образование

Пожалуйста, укажите самый высокий уровень образования, который Вы

закончили на данный момент:

• Ниже, чем средняя школа

• Средняя школа

• Диплом бакалавра или эквивалент

• Диплом магистра или эквивалент

• Доктор наук или эквивалент

• Other:

Страна происхождения

Пожалуйста, укажите свою страну происхождения


Ваши ответы на вопросы анкеты были сохранены. Большое спасибо за Вашу

помощь в проведении исследования!

35

Appendix 4

Normalised Responses

Table Appendix4.1 contains normalised responses ‘other’ to the question regarding

the perception of the visual stimulus

Table Appendix4.1. Normalised responses ‘other’ to the question regarding the perception of

the visual stimulus

In which survey it is occurs

N of the row in

the survey

Text of the ‘other’ response

Translation into English

(if the response is in Russian

or in Latvian)

Rotation speed

of the

lines rpm

Normalised response

ENG 1-15

29 where the two lines nearly meet, the

flashing line appears to lag a little behind the other line, also a little lean backwards.

- 10 Y

RU 15-1 6 мигающая линия несколько

отклонена от места соприкосновения с основной, как и смещена от самого этого месста

the flashing line is

somewhat sloping in the place where it

touches the main line as well as it is is shifted from that

place

15 Y

ENG 15-1

124 the flashing line is tilted with respect to

the solid line

the flashing line is tilted with respect to

the solid line

the flashing line is slightly tilted with respect to the solid

line

- - -

10

15 5

Y

Y

Y

perception of the flash-lag effect - ut · the perception of the flash-lag effect is caused by the...

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