Influences of hue differences in photos on perceived emotion

Transcription

1 Influences of hue differences in photos on perceived emotion Emiel Hollander ABSTRACT This research investigates whether hue differences in photos have influence on the emotions perceived in these photos. Participants were shown three photos with different subjects and colour casts, and were asked to rate four given emotions on a scale from zero to five for each photo. Results look promising; a negative colour cast causes far less positive responses and more negative responses for photos with positive content. Further research needs to be done for photos with a positive colour cast. 1. INTRODUCTION Every day we are confronted with shocking or amusing photos in newspapers and magazines. Each of these photos tells its own story. Few photos leave the viewer emotionless; most photos arouse a certain emotion. This is why editors sometimes choose to alter photos that will appear in print. People might be offended by these photos; the emotions those photos evoke will be too strong. Good examples of this are the several versions that exist of a photo taken shortly after the terrorist bombings in Madrid in 2004 [NEW04]. Some newspapers chose to alter parts of the photo to hide the most shocking content. Colours arouse emotions as well. Take a look at the different colours around, on websites, on billboards, etc. This paper focuses on the combination of colours and images. Do the colours in the image have any influence over the emotions felt for that image, or are the emotions aroused by the content far too strong for colours to have any influence? Are we able to predict the influences of these colour casts on the emotions perceived from these photos? Results of this research may be used to further tweak the emotion to be perceived from a photo by adding a colour cast. Shopping websites might profit from this by choosing the correct colours for their photos. It may also be useful in a virtual reality environment, where a change of hue might intensify the emotion conveyed by the scene. The first part of the paper looks into earlier research that has been done regarding colours, photo content and emotions. Based on this research, a problem statement has been made, which is explained in the next section. The fourth part clarifies the research method that has been used. Finally the results of Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission. 4th Twente Student Conference on IT, Enschede 30 January, 2006 Copyright 2006, University of Twente, Faculty of Electrical Engineering, Mathematics and Computer Science this research are presented and discussed. 2. EARLIER RESEARCH Research papers are available on the subject of emotions aroused by the contents of a photo as well as the topic of colour and emotions. 2.1 On emotions There are several ways to measure emotions. Some writers suggest that each emotion is built up from three factors: valence, arousal and dominance. Russell and Mehrabian [RM77] did research into this matter and found that these three factors or dimensions can be further described as follows. The first of these factors, valence or pleasure-displeasure, identifies how pleasant the emotion is, or, as Hanjalic and Xu [HX05] describe it, the type of emotion. Like the other two factors, this is a continuous scale. The scale for valence ranges from unpleasant to pleasant. The second factor is arousal, which describes the intensity of the emotion. Russell and Mehrabian describe the different states of arousal as a continuous range as well, ranging from sleep through intermediate states of drowsiness and then alertness to frenzied excitement at the opposite extreme. The final dimension is called dominance or control. It identifies the amount of control one feels to have over the emotion. This can vary from the feeling to have no control over the emotion at all on one end, and feeling influential and in control on the other end. According to Russell and Mehrabian, a person is constantly in an emotional state. This state can be described as a point in the three dimensional space that has just been described. According to them, these three independent and bipolar dimensions are necessary and sufficient to adequately define emotional states. Another way to measure emotions, which is far more convenient to let people assess their emotions themselves, is by using Plutchik s primary emotions or Ekman s basic emotions. According to Hårleman [Hår04], Plutchik found eight primary emotions a person can feel. These emotions are: fear, anger, sadness, joy, acceptance, disgust, anticipation and surprise. Any combination of these emotions will define the emotional state the person is in. Hårleman says that Ekman s basic emotions are similar to the primary emotions Plutchik found. However, instead of anticipation, Ekman s basic emotions include contempt. Measuring emotions using this theory can be done by letting a person assess for each emotion in what degree they feel this emotion. Letting someone answer this for these primary emotions is easier then letting someone answer their position on the three-dimensional scale of valence, arousal and dominance.

2 2.2 Images and emotions A photo can convey numerous emotions. Quite a few questions can arise when looking into this issue. How are people aroused by the content of a photo? Does this arousal appear only with certain types of photos, and if yes, with which types? Which emotions occur when people are aroused by a photo? Research into this matter has been done amongst others by Bradley et al. in [BCC01]. They based their research on physiological reactions measured with humans during picture perception. Measuring was done on, amongst others, heart rate and skin conductivity. They say that by looking at unpleasant pictures, the human defence system can be activated. A human reacting to an unpleasant picture is in a state analogous to that of the freezing animal. Viewing an unpleasant image causes a shift of attention starting with assessment of the situation, and ending with action, e.g. the need to fight or flight. This is just like an animal that is threatened by a predator. Pictures that directly activate the defence system therefore arouse the most unpleasant emotions. According to Bradley, images of predators attacking and death or mutilation of a member of the same species will evoke the defence system most, and will thus cause the most unpleasant emotions. In practice, a mere photo will hardly ever cause enough arousal to let the viewer really freeze and prepare for fight or flight. However, some indications that the defence system has at least been activated to a small extent are indeed measurable, e.g. by heart rate and skin conductivity, amongst others. With positive, or appetitive, motivation, things are a bit more complicated. A positive reaction on certain objects is only given when a person is in a certain mood. An example: you only react to food positively when you are hungry. The only exceptions to this rule are erotic images; these always arouse a positive emotion. Looking at a pleasant image causes an attention shift as well, say Bradley et al. This shift starts with initial attention too, and also ends with action. However, this action will be a positive one, based on a human or animal s natural reaction to this kind of stimuli. A positive photo will also evoke certain systems. Indications that these systems have been activated are again measurable. As with negative subjects, there are also some positive subjects that are just as pleasant as erotic images, but cause less arousal. Adventure and sports are two of these positive categories. Using these theories, the authors conducted an experiment which measured physiological reactions to certain photos. Based on these reactions they rated several subjects on a scale from pleasant to unpleasant. 2.3 Colours and emotions Numerous authors have done research in the field of colours and emotions. It has become clear that a certain colour can bias the perceived emotion of the viewer. Ou, Luo, Woodcock and Wright have created a colour emotion model that predicts how a colour scores on different colouremotion scales in [OLW04]. This model is based on the results of an empirical psychophysical experiment, in which observers assessed twenty colours on ten bipolar colour-emotion scales. Based on this experiment, the authors developed a threedimensional colour emotion space for single colours, that classifies colours according to their colour heat, colour weight and colour activity. These three classifications are based upon the colour-emotion scales that were used to question the observers. After that, the authors proceed to develop models for the classifications used in the colour emotion space, as well as for some of the colour-emotion scales. A comparison has been done between earlier models and the ones just developed. It was seen that the colour models of the three studies that were compared, matched well with each other. Kaya and Epps [KE04] tested emotional responses on five principal hues, being red, yellow, green, purple and blue, five intermediate hues like e.g. yellow-red or green-blue, and three achromatic colours: white, grey and black. Participants were shown each colour and were allowed to state only one emotional response per colour. They specified the colours they used using the Munsell system. The principal hues showed the largest amount of positive responses, with green and yellow scoring highest. Remarkably the hue yellow-green scored lowest with the intermediate hues, eliciting feelings of sickness and disgust. The achromatic hues grey and black also scored very low on positive responses. Kaya and Epps mainly focus on colour association with objects or physical space. They talk about respondents associating autumn or Halloween with certain colours, and conclude that the emotion felt with a certain colour is highly dependent on personal preference and ones past experience. Valdez and Mehrabian conducted similar research in [VM94]. They criticise other research, and mention several problems in these papers. The first problem mentioned is the fact that the colour samples used are underspecified and do not use common colour systems, while the second problem they see is the fact that the techniques used to have participants identify emotions are disputable. To solve this second problem, Valdez and Mehrabian developed a system that classifies emotions based on high or low pleasure, arousal and dominance. This system allows eight different types of emotions. An example of such a type of emotion is the one that consists of high pleasure, low arousal and high dominance (abbreviated by the authors as +P- A+D). Valdez and Mehrabian describe this type of emotion as comfortable, leisurely, relaxed, satisfied, [and] unperturbed. They used this method to let participants rate a selection of colours. The results were then used to find a function from wavelength to pleasure, arousal and dominance. Their results differ a lot from the results we ve seen so far. Valdez and Mehrabian found that blue and green are the most pleasant colours, while yellow is the most unpleasant colour. Yellow however scores higher on arousal and very high on dominance. The colour with the highest score on arousal is green-yellow, which also scores highest on dominance. Their results might differ so much from the results we have seen earlier because of the different system for measuring emotions. The system used by Valdez and Mehrabian utilizes a completely different concept than the systems used in other papers, which all use more or less similar systems. Hårleman [Hår04] did research in full scale rooms on influences of colour on emotion. She found that yellow causes

3 pleasure and joy, while green causes acceptance. All colours cause some negative emotions. Warm colours cause mostly disgust and anger while cooler colours cause disgust and sadness. Meerum Terwogt and Hoeksma did research on colour and emotion preferences with three age groups [MTH95]. They found that the emotion and colour preferences were consistent within each age group, but differed from one age group to another. The participants were first presented with two colours or two emotions. They were then to answer a question like Which of these two colours do you feel is the most beautiful one? After this, participants were asked to link emotions and colours to one another. For adults, Meerum Terwogt and Hoeksma found that yellow and green arouse happiness. In addition, yellow also aroused anger and a little aversion, while green aroused a little sadness. Black arouses negative emotions like anger, sadness, aversion and fear. White mostly aroused surprise. Further research into linking colours with emotions has been done by Hemphill [Hem96]. He conducted a questionnaire in which participants were asked to list, amongst others, their favourite colour, their emotional responses to colours and the reasons for their choices. He found that blue and green, and to a lesser extent yellow and read, aroused mainly positive emotions. White, pink, red and yellow also aroused some negative emotions, while grey and black aroused mostly negative emotions. Concluding we see that all authors more or less agree. The only outcasts are Valdez and Mehrabian, who seem to disagree with all other articles. All authors, except Valdez and Mehrabian, agree that yellow and green arouse positive emotions. With Valdez and Mehrabian, yellow is even the most negative colour of all. Valdez and Mehrabian found that blue and green are the most positive colours. This claim is partially supported by Hemphill. The other authors do not specifically mention blue as positive colour, while some do mention green. Only Valdez and Mehrabian mention a colour that is really negative according to them. This colour is yellow. While this colour is regarded as positive by other authors, these authors do not mention which colours they found to be negative ones. Only Hårleman mentions the kind of negative emotions aroused by certain colours. 3. PROBLEM STATEMENT Research clearly shows that both the content of a photo and a colour will arouse an emotion with the viewer. Question is what will happen when they are combined. Will they influence each other? Or will one of these aspects have such a large impact on the emotion perceived that the influence of the other aspect is negligible? Therefore, the main research question this paper answers is the following. How can different hues on a photo affect the emotion perceived while watching this photo? 3.1 Hypotheses The expected results for this research are that the negative colour cast causes participants to assess the photo more negatively, i.e. rate the negative emotions higher and positive emotions lower, while the positive colour cast causes participants to assess the photo more positively, i.e. rate the negative emotions lower and the positive emotions higher. The neutral emotions are used as reference. 4. RESEARCH METHOD To research this I selected three photos of which the content arouses a certain emotion with the viewer. I have altered these photos by applying a certain colour cast on them. Participants rated these photos on four different emotions. The research method is explained in the next paragraphs. 4.1 Measuring emotions As discussed in paragraph 2.1 there are several ways to measure perceived emotions. The method that was used in this research is the same as has been used by Hårleman [Hår04], and partially the same as has been used by Kaya and Epps [KE04], Ou et al. [OLW04] and Meerum Terwogt and Hoeksma [MTH95]. The participant is presented with a list of four emotions to choose from. The emotions the participant can choose from have been chosen from the list mentioned by Hårleman. These emotions are fear, anger, joy and surprise. As you can see this consists of two positive and two negative emotions which I think are easy to distil from a photo. This decision was based upon the little amount of time available to conduct the research, as well as the limited number of participants available within the specified time. In addition, each extra emotion increases the number of needed participants in the research. Given these circumstances the chosen method performs rather well. I have chosen two positive and two negative emotions so there is no bias present towards positive or negative emotions in the number of emotions the participant has had to assess. The participant has rated each emotion on a scale from zero, which means that the emotion can not be perceived from the photo at all, to five, the emotion can be perceived a lot from this photo. 4.2 Selecting photos As said before, three photos have been selected to conduct this research. One photo has been chosen so that its content arouses a negative emotion, one with a content that arouses a positive emotion and finally one with a neutral content. All photos have been shown to the participants in colour. They have only been converted to black and white for use in this paper. By using photos in colour, I can achieve more subtle hue changes. When the hue of a greyscale photo changes this is very obvious; I hope to inflict subtle hue changes on a colour photo that are still clear enough to achieve the changed perceived emotion I m after, without creating an unrealistic photo. Bradley et al found out in [BCC01] that using colour or greyscale does not affect the felt emotions for the subject. Most of the experiments researching emotions aroused by photo content have been conducted using IAPS: the International Affective Picture System. This is a set of normative emotional stimuli for researchers to use, developed by the NIMH Center for Emotion and Attention (CSEA) at the University of Florida According to the instruction manual [LBC97], using this set of photos gives researches a number of advantages, e.g. facilitating the comparison of results across different studies.

4 In this research I was not able to use photos from IAPS because there was no time to order the system. Figure 1. Negative content Instead, I searched for appropriate pictures myself based upon several categories mentioned mainly by Bradley et al. in [BCC01]. I found applicable photos on a site called stock.xchng [SXC05] which offers copyright free photos for download. According to Bradley et al [BCC01], pictures with attacks or mutilation cause the highest unpleasant arousal. However, since I want the colours I alter the photos with to still have effect on the emotions felt, I chose not to select subjects with highest arousal. Instead I chose content that caused a little less arousal, but was found to be just as unpleasant as the subjects that do cause highest arousal. A little more at the centre of Bradley s scale are illness, contamination and accidents. I decided to pick my photo from one of these three categories. The photo I chose to reflect negative emotions can be seen in figure 1. The burning barn is a photo of an accident that is still threatening to most people. It is unpleasant enough to arouse negative emotions, but not too negative. I chose to select a subject in the category of adventure or sports for a positive emotional reaction. Most sports photos are very colourful; the shirts of people practising sports usually have vibrant colours, and with water sports there is a huge amount of blue caused by the water. I found a photo of children playing a soccer match, which contained a wide scale of not too vibrant colours. It is shown in figure 3. Finally a photo with a neutral subject was needed. In the middle of Bradley s scale are household objects and mushrooms. It was impossible to find a neutral photo of a household object without the rest of the room causing emotions. I therefore chose another subject, which aroused slightly positive emotions in Bradley s research: nature. The neutral photo consists of a landscape with a village. I am aware that this photo arouses slightly positive emotions, but the arousal value is low enough that I think it suffices as photo with a neutral content. The photo is shown in figure Selecting colours These photos were all slightly altered with a certain colour cast. This cast was especially chosen to arouse certain emotions with the viewer. The decision was mainly based on the results of Hårleman s research [Hår04] since she used the set of emotions that I have chosen to use a subset from. Figure 2. Neutral content People tend to be positively aroused by erotic photos of the opposite sex, say Bradley et al. But since this is also a subject that causes high arousal, I chose not to select it. Further down the scale are adventure, sports and food. Food has the problem that it only evokes a positive reaction when one is hungry, so therefore I did not select a photo with this subject as well. Figure 3. Positive content The colours I chose to go with different emotions really differ from the results found by Valdez and Mehrabian in [VM94]. Because they have used a completely different system for measuring emotions and I have not used this system, nor have the other papers I based my decisions on used this system, the results of their research have not been used to determine which colours to modify the images with. I have altered the photos to add colour casts of colours that arouse a negative and a positive emotion. I also added a photo without any colour cast to the research to be able to measure the differences between this neutral cast and the two other colour casts. As we have seen in paragraph 2.3, the colours yellow and green arouse mostly positive emotions. The combination of these two colours however is seen as negative. For this reason I have chosen a mainly yellow colour cast with in addition a slight green cast as positive colour cast. This way I hope to evoke mostly the positive emotions felt with yellow and green.

5 Blue and purple were mostly cited as colours that arouse mostly negative emotions, as can be seen in paragraph 2.3 as well. Based on this information, I chose to use a magenta-blue colour cast for negative emotions. Finally, each photo has also been presented with a neutral colour cast. To make sure this photo is as neutral as possible I used Photoshop to remove any colour cast that might be present in the original photo. All photos have been altered using Adobe Photoshop s Variations function. I adjusted highlights and shadows as well as midtones. However, the midtones could not be altered as much as the highlights and shadows without creating an unrealistic photo. Therefore I made finer adjustments to the midtones and more coarse adjustments to the highlights and shadows. 4.4 Experiment website For people to participate in the experiment, a website was created. A website enables people to easily participate wherever they are. This has advantages as well as disadvantages. An advantage is that a participant can take part in the experiment very easily. He can sit down wherever he wants to and answer the questions. A quiet place without many distractions can be chosen, as well as a quiet moment so that the participant can assess the emotions as good as possible. This advantage is at the same time the largest disadvantage as well. There is no influence over where the participant takes part in the experiment, and by which things he is distracted. He could go and sit in a noisy environment, and answer the questions in a grumpy mood. To avoid this, the participant first gets to see a screen containing instructions before he starts with the experiment. These instructions prepare him for the questions that will be asked and request him to take certain precautions. The first precaution the site asks the participant to take is to make his browser appear full screen. This diminishes distractions from other computer programmes running, as well as from colourful buttons on other parts of the screen. Secondly, the participant is given the list of emotions in advance. He is asked to have a close look at the emotions to be prepared to answer them with regard to the photos. He is also given the instruction to rate the emotions for three photos, and to press a button when he is done with one particular photo. The website always displays the photos in the same order. The photo with negative content (see figure 1) always comes first, then the photo with neutral content (see figure 2) and finally the photo with positive content (see figure 3). This order might influence the emotions people feel with the second and third picture; they might be more positive after viewing the first photo. This could be taken into account while viewing the results. On the other hand, the differences are not very large, since only the photos themselves are shown in the same order each time. The order of the different colour casts changes with each participant. So all three variations of the photo with the same content have the same bias caused by the order the photos have been shown in. While the order of the photos stays the same with each participant, the order of the colour cast changes each time. To make sure there is enough data available for each colour cast, the order each cast is shown to a particular participant is not chosen at random. With three colour casts, six different orders to show these colour casts in can be made. Each time a new participant takes part in the experiment, the website chooses the next order of colour casts in line. When the six different orders have all been done, it starts over with the first order of casts again. This assures there is enough data available for all the colour casts. The answers from all participants are collected and stored in a database, so that in the end they can easily be accessed to determine the results of the experiment. 5. RESEARCH RESULTS A total of 22 people participated in the research. They have each rated three photos, which gives a total of 66 measurements. There are therefore 22 ratings for each photo as well as 22 ratings for each colour cast. While discussing the results, and in the various graphs shown, I refer to Photo 1 for the photo with negative content as shown in figure 1. Photo 2 is used for the photo with neutral content as shown in figure 2, and finally I refer to the photo with positive content, as shown in figure 3, as Photo 3. This is also the order in which the photos have been presented at the experiment website. The graphs are presented per photo, having three bars for each emotion. The leftmost bar represents the average of all the answers for the negative colour cast, the centre bar represents the average of all the answers for the neutral colour cast and finally, the rightmost bar represents the average of all the answers for the positive colour cast. 5.1 Negative content This section discusses the results for the photo with negative content. The results can be seen in figure 4. Figure 4. Results for photo 1 First of all it is visible that the content of the photo was correctly chosen. The participants have chosen mostly negative emotions for this photo. It is plainly visible that the differences between different colour casts exist mainly between the neutral colour on one side and both colour casts on the other side.

6 The positive colour cast lessens the amount of negative reactions, for anger in particular. There is no increase of positive emotions however. This might indicate that the content of the photo arouses the viewer too much for the colour to have very much influence. Table 1. Standard deviations for photo 1 Cast Fear Anger Joy Surprise Negative Neutral Positive The immense changes for surprise are interesting. The photo with neutral colours causes a lot more surprise than both colour casts. However, as we can see in table 1, the standard deviation for surprise with the neutral photo is much higher than for the two colour casts. This means that, although the average is higher, the participants answers were also more widespread. As we see in figure 4, surprise can be seen as both a positive and a negative emotion. While it has initially been selected as a positive emotion, people also selected it with this photo containing negative content. That it has positive aspects as well becomes clear in the next sections about photos with neutral and positive content. The negative colour cast seems to have the same effect on responses as the positive colour cast. However, the standard deviations for the positive colour cast are far lower than those for the negative colour cast. For the negative colour cast, participants chose more extreme values, while for the positive colour cast people stuck more to the average. Still, noting that a negative colour cast has been applied, the averages for fear and anger should have been much higher for this photo. Figure 4 clearly shows that for the negative colour cast the answers given for the emotions fear and anger are much lower than for the neutral colour cast. There is a possible explanation for the lower amount of negative reactions on the negative colour cast. The colour cast I applied consisted of blue and magenta. Since fire mostly consists of warm colours like red and orange, this might have decreased the impact of the fire itself on the emotion of the viewer, thus causing the participant in the experiment to select a lesser rating for these negative emotions. The same explanation could be used for the diminished responses that have been given for anger with the positive colour cast. Green and yellow also lessen the amount of red in the photo. 5.2 Neutral content As predicted when selecting it, photo 2 with neutral content aroused more positive emotions than intended. However, it is nearly not as positive as photo 3, and definitely not negative as photo 1, so, while not as neutral as the intention was, I still regard photo 2 as neutral enough for this research. The results for this photo are graphed in figure 5. It can be seen that for both colour casts, people have started rating this neutral content with negative emotions, although joy and surprise stay at roughly the same levels. Figure 5 however clearly shows that joy scored highest for the photo with a negative colour cast. For this cast, joy also has the lowest standard deviation. The values for joy only get lower with the neutral colours and positive colour cast. Table 2. Standard deviations for photo 2 Cast Fear Anger Joy Surprise Negative Neutral Positive Some authors indicated that, while yellow and green are positive colours by themselves, the combined cast arouses mainly negative emotions. This might be the cause for the lower scores for joy, and might explain the values of fear and anger for the positive cast. Figure 5. Results for photo 2 Fear and anger were also selected for the negative colour cast, as was expected when choosing this cast. 5.3 Positive content The results for photo 3 with positive content also show that the content itself was correctly chosen. The photo arouses mainly positive emotions. It also arouses much more positive emotions than the neutral photo. The results for this photo can be seen in figure 6. We again see that negative emotions have been selected for both colour casts, but not for the neutral photo. Table 3. Standard deviations for photo 3 Cast Fear Anger Joy Surprise Negative Neutral Positive The results for the positive colour cast are very different from what could have been expected based on the selected colours. While the aim was to arouse more positive emotions, this has not happened at all. The positive responses are for this photo also lower for the positive colour cast than for the neutral colours.

7 Also, for this photo as well as the photo with neutral colours, with a positive colour cast negative responses are higher than for the same photos with neutral colours. These results completely differ from what was to be expected. Figure 6. Results for photo 3 For the negative cast, the participants selected negative emotions as was expected. The average for joy however is higher than with the neutral colours and the positive cast. As discussed with photo 2, this might have to do with the positive cast that was selected. 6. CONCLUSIONS Conclusions can be drawn for each photo and each colour cast. Some photos and colour casts have aspects in common though. Comparing the results for photos, we see the negative photo on one hand and the other two photos on the other hand. The neutral and positive photos have similar results. Also, the positive and negative colour cast share a lot of results when compared to the photo variations with neutral colours. In essence it can be seen that a negative photo with a cast, regardless whether it is positive or negative, lessens the amount of negative emotions. Positive emotions are not really present with the negative photo at all, when we disregard surprise as an emotion that only has positive aspects. The neutral and positive photos show similar results. This may have to do with the fact that the content of the neutral photo was slightly positive to start with. On this photo any cast, regardless of which cast, has the same effect on negative emotions. Both the negative and positive casts arouse more negative emotions. Here, the positive cast causes the smallest amount of positive emotions while the negative cast causes the largest amount. Suspicions arise that, although yellow and green are related to positive emotions by themselves, the combination of these two colours indeed arouse negative emotions, as has already been suggested by several authors. 7. DISCUSSION The results of this research look promising. Colour casts do seem to have an influence over the emotions perceived while looking at a photo. The results for the selected positive colour cast however are not consistent with the other results. This may have several reasons. I may have selected wrong colours to arouse positive emotions for this colour cast. While yellow and green arouse positive emotions by themselves, several authors mention that the combination of these two colours arouses negative emotions. There is also a possibility that emotions are not affected in the way I thought they would be affected. I expected a positive colour cast to always have a positive effect on emotions felt when looking at that photo. This might not be the case at all. Further research needs to be done to support this claim. Another reason may be that it is hard to achieve positive emotions with a colour cast. A positive colour cast may have less effect on perceived emotions than a negative one. Also, the results for a negative cast on a photo with negative content are interesting. This negative cast causes the participants to select less negative emotions, opposite to what was to be expected. The reason for this might be the content of this particular photo. Fire is usually red, and when applying a blue-magenta colour cast, the influence of this red colour lessens. This will then lessen the amount of negative emotions chosen. Since only 22 people participated in this research, it is hard to say whether the results are reliable enough to draw actual conclusions. A larger experiment is needed to confirm these results. Since the average values for each emotion per photo are about the same for each colour cast, I can say that the photos have been well-chosen and had the effect I expected them to have. The differences between the colour casts however are not very clear. It seems like the colour casts have an effect on the perceived emotion, but I would suggest further research to support this claim. Standard deviations are fairly high, with a whopping 1.92 on surprise for the neutral photo with a positive colour cast. This is quite large for a scale from 0 to 5. The results furthermore show that surprise is not the best choice for a positive emotion. Surprise can be looked at in both a positive and a negative way. I chose surprise as second positive emotion, so that the amount of positive emotions the participant would have to assess would be the same as the amount of negative emotions. Using a website to conduct this research has several advantages. Participants can take part in the experiment wherever and whenever they want. They can go and sit in a quiet place to answer the questions. But, as mentioned before, a website also has some disadvantages. The participant could answer the questions in a grumpy mood. This might alter the answers this person gives in response to the questions. It might be worthwhile to redo the experiment in a more controllable setting. The order in which the images were shown might also have had influence over the results. The first image was always the one with negative content. This might alter the way someone feels over the more positive second and third picture. Randomizing this order will help avoid this. 7.1 Further research I would really recommend further research into this matter, as the first results look very promising. Research with a larger set of images would help to get more reliable results. Furthermore, having more participants will greatly enhance the reliability of

8 the results. Also selecting other hues to alter the photos with will help to achieve better results. Other research could also discard the decision I made to use positive and negative colour casts. As discussed, the effects of colour casts on photos might not be as I thought them to be. Selecting a number of casts, without giving them the predication positive and negative will clarify this. Further research could also be done using computer generated images, or virtual reality environments, to see whether there is any difference between these images, which of themselves are already less realistic than photos. 8. REFERENCES [BCC01] Bradley, Margaret M.; Codispoti, Maurizio; Cuthbert, Bruce N.; Lang, Peter J. Emotion and Motivation I: Defensive and Appetitive Reactions in Picture Processing. Emotion, vol. 1, no. 3, [Hår04] Hårleman, Maud. Colour emotion in full-scale rooms. In Proceedings of the Interim Meeting of the International Color Association, Porto Alegre, Brazil, November 3-5, 2004, [Hem96] Hemphill, Michael. A Note on Adult s Color- Emotion Associations. Journal of Genetic Psychology, vol. 157, no. 3, [HX05] Hanjalic, Alan; Xu, Li-Qun. Affective Video Content Representation and Modeling. IEEETransactions on Multimedia, vol. 7, no. 1, [KE04] Kaya, Naz; Epps, Helen. Color-emotion associations: Past experience and personal preference. In Proceedings of the Interim Meeting of the International Color Association, Porto Alegre, Brazil, November 3-5, 2004, [LBC97] Lang, P.J.; Bradley, M.M. and Cuthbert, B.N. International affective picture system (IAPS): instruction manual. Technical Report A-6. University of Florida, Gainesville, FL. [MTH95]Meerum Terwogt, Mark and Hoeksma, Jan B. Colors and Emotions: Preferences and Combinations. Journal of General Psychology, vol. 122, no. 1, [NEW04] cat_madrid_bombings.php Taken December 3 rd, [OLW04]Ou, Li-Chen; Luo, M. Ronnier; Woodcock, Andrée; Wright, Angela. A Study of Colour Emotion and Colour Preference. Part I: Colour Emotions for Single Colours. Colour Research and Application, vol. 29, no. 3, [RM77] Russell, James A. and Mehrabian, Albert. Evidence for a Three-Factor Theory of Emotions. Journal of Research in Personality, vol. 11, no. 3, [SXC05] stock.xchng. Taken November 26 th, [VM94] Valdez, Patricia and Mehrabian, Albert. Effects of Color on Emotions. Journal of Experimental Psychology: General, vol. 123, no. 4,