The Deception of the Eye and the Brain

Transcription

1 PROJECT N 12 The Deception of the Eye and the Brain Elisa Lazzaroli, Abby Korter European School Luxembourg I Boulevard Konrad Adenauer, 23, 1115, Luxembourg, Luxembourg S3 EN Abstract Key words: Optical illusions, brain, interpretation Optical illusions can be defined as the images we see with our eyes but are not actually real. It can be any information that the eye gives to the brain that is not a physical reality. Optical illusions are an error or a false assumption of the brain. They widen the mental horizons and make it clear that things are a little different than they seem. Optical illusions can reveal remarkable vulnerabilities of human visual perception. Optical illusions are particularly good adaptations of our visual system to standard viewing situations. These adaptations are hardwired into our brains, and thus can cause inappropriate interpretations of the visual scene. The brain is constantly constructing things, which helps you to survive. The phenomenon that our brain is constantly looking for known patterns in random structures with low information content is called pareidolia. Some of these constructions can be fiction: A theory a neurobiologist came up with to help explain why we see optical illusions is that they re due to the brain s attempt to see the future. These optical illusions occur during the slight time lag after light reaches the retina in your eye, before your brain translates it into a visual perception. When the brain attempts to generate a perception, it is basically taking a guess at the near future by trying to fast-forward a tenth of a second. Due to this "neural delay", you might not be perceiving an image as it actually is, but as you expect it might soon be. Illusions occur when the brain attempts to perceive the future, and those perceptions don't match reality. 1

2 Although there is no single reason illusions take place, another possible explanation is that the brain is a limited structure with limited resources, including its number of neurons, wires, and neuronal connections, so in some cases, illusions may be due to the brain's need to take shortcuts. Simply put, the brain might need to quickly give more importance to some features in a visual scene than others. 2

3 1. Introduction Optical illusions are something that have been tricking people for centuries. We have all experienced that weird feeling when we look at an optical illusion and suddenly everything started turning. An illusion is proof that you don't always see what you think you do because of the way your brain and your entire visual system perceive and interpret an image. Optical illusions occur due to properties of the visual areas of the brain as they receive and process information. In other words, your perception of an illusion has more to do with how your brain works -- and less to do with the optics of your eye. No one perceives one image in exactly the same way as another person. For our project, we decided to take a less flashy approach, and used subtler illusions, ones that could take time to decipher or some that involved an image in which it is unclear so as to what it is showing. We thought that it would be easier to work with these, as each participant would have a time or a choice of two options. By doing this we were able to analyse our data. The aim of our project is to identify how the characteristics of a person affect the way that the person reacts to an optical illusion. More specifically, we want to focus on how inherent physical characteristics or skills have an effect on their answers or on their response time in an optical illusion. This project will lead us to identify a pattern between a participant and his/her answers. 2. Materials To test our participants, we used - A stop watch And the following optical illusions: - Bad Eyes 3

4 - Dot Box - Bird In The The Hand (BITTH) - Book 4

5 - Girl Picture - Vase / two faces - Dog Face 5

6 - Cube missing a corner / box in a room 3. Methodology In our project, we worked with 35 participants in total. We divided our participants in two main categories: Adults and Under Eighteen (U18). In each category, we created four subcategories: Gender, Glasses, Eye colour, Mathematical and Scientific Abilities. The subgroups of each subcategory are described in the following table. Subcategory Gender Glasses Eye colour Mathematical and scientific abilities Subgroups 1. Male 2. Female 1. Glasses or Contact lenses 2. No glasses or Contact lenses 1. Brown 2. Blue 3. Green 1. Marks 6-8 in maths and science 2. Marks 8-1 in maths and science We took the participants into a quiet room one by one before starting the experiment. 6

7 1. First, we asked our participants what age group they are a part of (if they are under 18 or adults), their eye colour, if they wear glasses, and their mathematical and scientific abilities 2. Then, we showed our participants a series of eight optical illusions, four of them were timed and the other four had two options the participants had to choose from. Each image from the categories is shown one by one in alternation. 3. The optical illusions are described below: o The first illusion is called Bad Eyes (shown above). We asked the participant to stand at a certain point and to look at the image and eventually it could take a while or not at all they would be able to decipher two words: BAD EYES o The second illusion is called Dot Box. In this case, we simply asked them if they saw the red dot inside the box or on the outside surface of it o The third one, A Bird In The The Hand (BITTH), was the second timed illusion. In reality, there is a second the in the triangle, but we just told the participants to read what was written out loud (until they found the mistake on their own) o The fourth illusion is simply called Book. We showed the participants the image and asked them which way the open book was facing: as if we were reading it (cover) or as if they were reading it? (text) o The fifth illusion is named Girl Picture. We asked the participant to stand in front of a white wall or board. They were to stare at the red dot on the girl s nose for thirty seconds, and when those thirty seconds were up, to look up and blink, staring at the white surface in front of them. The image would then appear, in the inverted colours, and most likely move around. When the picture was gone, the participant had to notify us. o Our sixth illusion is Vase / Two Faces. The participant was instructed to look at the image and tell us what they saw: a vase or two faces? o The seventh illusion is Dog Face. The participants were shown the image and they had to describe it to us, until they realised that it is in fact a dog s snout which is covering the girl s face. o The eighth and final illusion is an image of either a cube missing a corner, or a box in a room. The participants had to look at the image and tell us what they saw first: a cube missing a corner or a box in a room. 7

8 Time (minutes) 4. Results We have analysed our results, and have noticed some patterns. Below are some of our graphs: UNDER 18 We started off by analysing some data from the under 18 category. Glasses / No glasses (Bad Eyes) Under 18 4,5 4 3,5 3 2,5 2 1,5 1,5 fastest slowest average glasses no glasses Here we see that people who wear glasses (or contact lenses) are faster at seeing the words BAD EYES on average than the people who don t wear glasses. Also, our fastest and slowest participants within the glasses and no glasses categories have a significant difference: the glasses wearers took half the time the people without glasses took. 8

9 Time (minues) percentage Gender (Dot Box) Under Female Male Total Inside Outside In this graph, we see that about 2/3 of both female and male participants saw the dot to be inside the box, and the other 1/3 saw it on the outside. This shows that whether the participant was male or female had little effect on the results. 1,8 1,6 1,4 1,2 1,8,6,4,2 Gender (BITTH) Under 18 fastest slowest average female male Here we see that males are slightly slower at spotting the second the than the females (on average). The fastest female and male were equally fast, but the slowest male participant was a fair bit slower than the slowest female. 9

10 percentage percentage Gender (Book) Under male female total text cover This graph also shows that, once again, the gender had no effect on the results. For both the females and males, a bit less than 2/3 saw the book as if they were reading the text in it, and the same goes with the total Eye colour (Vase / Two faces) Under 18 blue green brown total vase two faces In this graph, we see that the eye colour does influence what the participants saw: a white vase or two black faces. The light colours (like blue and, to some extent, green) leaned more towards seeing the white vase, but instead the darker colours (brown) mostly went for the two black faces. 1

11 percentage Under 18 and adults comparisons We decided to do a few graphs to compare the two categories: Under 18 and adults. 12 Eye colour (Book) Under 18 and Adults Brown U18 Green U18 Blue U18 Brown AD Green AD Blue AD Total U18 Total AD Total U18 + AD cover text Here we see that the eye colour and the fact that the participant is an adult or is under 18 does influence the results. The Under 18 participants didn t have any very drastic differences in percentage, except for blue eyed participants, of which about 2/3 picked cover. In the adults, instead, nobody with brown eyes picked text, and in the other categories there was a high preference for cover. In the green eyes category, 4/5 of the adults picked cover, but more Under 18 participants picked text. The blueeyed participants had more similar results. Both the adults and Under 18 participants had about 2/3 choose cover, although more picked cover in the adults category. In total, about half of the under 18 participants picked text, and the rest (slightly over half) picked cover. For the adults, in total 8% of them picked cover. Finally, looking at both adults and under 18 we see that the preference was cover by quite a bit, with about 2/3 of the participants picking it. 11

12 time (minutes) Gender (Bad Eyes) Under 18 and Adults Fastest Slowest Average Female U18 Male U18 Female AD Male AD This graph compares the speed at which the participants saw the words BAD EYES. On average, the males from the under 18 category were slowest, but the males from the adults category were the fastest. In the under 18 category, the female s fastest participant was slightly slower than the male s fastest participant, but the female s slowest participant took half the time the male s slowest participant took. The adults were a lot faster than the under 18s. Both the female s and male s fastest and slowest participants took the same amount of time, but on average the males were slightly faster than the females. We can see that the adults were a fair amount faster than the under 18s, in all the categories, and that there was a lot more variation in the results of the Under 18 males. 12

13 percentage Glasses / no glasses (Vase / Two faces) Under 18 and Adults glasses U18 no glasses U18 glasses AD no glasses AD glasses total no glasses total total vase two faces In this graph, we see that the white vase was picked in majority. In the under 18 category, the two black faces were picked more frequently than the white vase, the participants without glasses picking vase and two faces equally, whilst the participants with glasses picked the two faces a bit more frequently. The adults, instead, picked the vase a lot more. Unlike the under 18s, there was a lot more variation in both the glasses category and the no glasses category. 4/5 of the glasses wearers picked vase (unlike the under 18, who preferred the two faces), and a bit less than 2/3 of the participants who don t wear glasses picked two faces (the under 18 without glasses had picked vase and two faces evenly). In total, participants with glasses preferred the vase, and the participants without glasses the two faces. 13

14 time (minutes) percentage Adults Finally, we analysed our data from the Adults category Eye colour (Dot Box) Adults blue green brown total inside outside This graph shows us that for the adults, their eye colour does change their results. From all our adult participants, only some with blue eyes saw the dot to be on the outside of the box, whilst everyone else saw it inside the box (all the participants with green and brown eyes).,3 Mathematical and Scientific abilities (Girl picture) Adults,25,2,15,1,5 fastest slowest average 6 to 8 8 to 1 It is shown through this graph that on average, participants with strong mathematical and scientific instincts saw the girl for less time than the participants who don t have very strong mathematical and 14

15 percentage scientific instincts. The fastest participant (to have the girl disappear) with strong mathematical and scientific instincts saw the girl for about ¼ of the time the fastest participant which doesn t have very strong mathematical and scientific instincts took. The slowest participant (to have the girl disappear) with strong mathematical and scientific instincts saw the girl for longer than the slowest participant which doesn t have very strong mathematical instincts. 12 Glasses / No glasses (Box / Cube) Adults glasses no glasses total Box in a room Cube missing a corner Here we see that adult participants with glasses saw with more frequency a box in a room by far, with only 1% of them seeing a cube missing a corner. Half of the participants without glasses saw a box in a room, and the other half a cube missing a corner. In total, the majority of the participants saw a box in a room, rather than a cube missing a corner. 15

16 time (minutes) time (minutes) Gender (BITTH) Adults 1,6 1,4 1,2 1,8,6,4,2 fastest slowest average female male In this graph, we see that females were faster than the males to notice the second the, both on average and with the slowest participant (who saw it in about ¼ of the time the slowest male participant took). The two genders were only the same in time when it comes to the fastest participant from both genders.,7,6,5,4,3,2,1 Mathematical and Scientific abilities (Dog Face) Adults fastest slowest average 6 to 8 8 to 1 Finally, this graph shows that participants with strong mathematical and scientific abilities were faster on average to realise that a dog s snout covered the woman s face, in comparison with the participants who don t have very strong mathematical and scientific abilities. The slowest participant 16

17 with strong mathematical and scientific abilities took about half the time the slowest participant of the other category took. At last, the fastest participant from both the categories took the same amount of time to spot the dog. 5. Discussion Our analysis has shown that the way a person reacts to an optical illusion does depend on his/her characteristics. Here we present our most important findings. General findings 1. Adults are faster than the Under 18s as their response time is shorter. 2. People with glasses or contact lenses are quicker than those without glasses. Findings sorted by optical illusion BOOK: The gender and the eye colour do not affect the choice of a participant. DOT BOX: The gender and the eye colour do not affect the choice of a participant. GIRL PICTURE: People with strong mathematical and scientific abilities see the girl for less time that those who don t have a strong background in the sciences. BOX/CUBE: Most of the participants see a box in a room. BITTH: Female participants are faster than males to notice the second the in both categories (U18 and Adults). VASE/TWO FACES: The eye colour affects the choice of a participant. Participants with dark eyes tend to choose the black figure and participants with light eye colours the white option. We didn t notice any differences between glasses wearers and adults/u18 participants, which means that both categories do not affect the choice of a participant. Our study has limits as the findings describe our sample and our results cannot be generalised to the whole population. In order to extract general rules on how each characteristic affects the way a person reacts to an optical illusion we need to continue our study with more participants. 17

18 6. Conclusion The optical illusions are divided in many categories based on their type and how they work. Each category works with a specific way and cheats the brain. It would be useful to identify how the characteristics of humans affect the way they interact with each category of illusions. This will lead us to realise how each category of illusions works. We have been able to identify some patterns due to different characteristics, and have found that there are some links here and there, but we would need to look more into it so as to find more details. 7. Acknowledgements We would like to thank our mentor and physics teacher Ms. Georgia Theodoulou for all her help, guidance, and patience. 8. References