The Print Shop at Sheffield Hallam University is thanked for providing high quality reproductions of the portraits used in this study. Michael Pickard and Jonathan Dean are thanked for their valuable insights.

The protocol was approved by the Faculty Research Ethics Committee at Sheffield Hallam University for studies on human subjects.
1. Inter-observation Stage
<ol>
	<li>Identify how and why La Bella Principessa&#39;s expression appears ambiguous.
	<ol>
		<li>Display a good quality, frameless and exact sized foam backed digital copy of La Bella Principessa (33.2 cm in height x 23.8 cm in width) on an easel in diffuse lighting.</li>
		<li>Have four participants discuss the ambiguous expression in...

<ol>
	<li>Kemp, M., Cotte, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> La Bella Principessa: The Story of the New Masterpiece by Leonardo da Vinci. , (2010).</li><li>Livingstone, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+it+warm?+Is+it+real?+Or+just+low+spatial+frequency.">Is it warm? Is it real? Or just low spatial frequency.</a> Science. 290 (5495), 1299 (2000).</li><li>Soranzo, A., Newberry, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+uncatchable+smile+in+Leonardo+da+Vinci's+La+Bella+Principessa+portrait.">The uncatchable smile in Leonardo da Vinci's La Bella Principessa portrait.</a> Vis.Res. 113, 78-86 (2015).</li><li>Silverman, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Leonardo's Lost Princess. , (2012).</li><li>Kemp, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Leonardo. , (2011).</li><li>Kemp, M., Cotte, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> La Bella Principessa. The Story of the New Masterpiece by Leonardo da Vinci. , (2010).</li><li>Bozzi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=L'interosservazione+come+metodo+per+la+fenomenologia+sperimentale+[Interobservation+as+a+method+for+experimental+phenomenology].">L'interosservazione come metodo per la fenomenologia sperimentale [Interobservation as a method for experimental phenomenology].</a> Giorn. It Psic. 5, 229-239 (1978).</li><li>Bozzi, P., Martinuzzi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Un+esperimento+di+interosservazione+[An+experiment+of+interobservation].">Un esperimento di interosservazione [An experiment of interobservation].</a> Riv. Psic. 74, 11-46 (1989).</li><li>Kubovy, M., Wilson, R. A., Keil, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gestalt+Psychology.">Gestalt Psychology.</a> The MIT Encyclopedia of the Cognitive Sciences. , 346-349 (1999).</li><li>Harr&#233;, R., Secord, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Explanation of Social Behaviour. , (1972).</li><li>Asch, S. E., Guetzkow, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+group+pressure+on+the+modification+and+distortion+of+judgments.">Effects of group pressure on the modification and distortion of judgments.</a> Groups, Leadership and Men. , 177-190 (1951).</li><li>Setlur, V., Gooch, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+that+a+smile?+Gaze+dependent+facial+expressions.">Is that a smile? Gaze dependent facial expressions.</a> NPAR 2004 Proceedings 3rd int. symp. on non-photorealistic animation and rendering. , 79-151 (2004).</li><li>Ekman, P., Friesen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Unmasking the face. A guide to recognizing emotions from facial cues. , (1975).</li><li>Latto, R., Russell-Duff, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+oblique+effect+in+the+selection+of+line+orientation+by+twentieth+century+painters.">An oblique effect in the selection of line orientation by twentieth century painters.</a> Emp stud. Arts. 20 (1), 49-60 (2002).</li><li>Glaser, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Basics of Grounded Theory Analysis. , (1992).</li><li>Glaser, B. G., Strauss, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Discovery of Grounded Theory: Strategies for Qualitative Research. , (1967).</li><li>Strauss, A., Corbin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grounded+theory+research:+Procedures,+canons,+and+evaluative+criteria.">Grounded theory research: Procedures, canons, and evaluative criteria.</a> Qual. Soc. 13, 3-21 (1990).</li><li>Strauss, A., Corbin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Grounded Theory in Practice. , (1997).</li><li>Kurtz, T. E., Arscott, J., Taggart, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Gold Edition Reference Guide for the True BASIC Language System. , (2010).</li><li>Z&#246;llner, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ueber+eine+neue+Art+von+Pseudoskopie+und+ihre+Beziehungen+zu+den+von+Plateau+und+Oppel+beschrieben+Bewegungs+phaenomenen.+[On+a+New+Kind+of+Pseudoskopics+and+its+Relationship+to+the+Motion+Phenomena+Described+by+Plateau+and+Oppel].">Ueber eine neue Art von Pseudoskopie und ihre Beziehungen zu den von Plateau und Oppel beschrieben Bewegungs phaenomenen. [On a New Kind of Pseudoskopics and its Relationship to the Motion Phenomena Described by Plateau and Oppel].</a> Annalen der Physik. 186, 500-525 (1860).</li><li>Hering, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Beitr&#228;ge zur Physiologie. I. Zur Lehre vom Ortssinne der Netzhaut [Contributions to physiology I about the doctrines of local senses of the retina. , (1861).</li><li>Orbison, W. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+correction+of+an+omission+in+"Shape+as+a+function+of+the+vector+field".">The correction of an omission in "Shape as a function of the vector field".</a> Am J.l of Psyc. 52, 309 (1939).</li><li>Anstis, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+furrow+illusion:+Peripheral+motion+becomes+aligned+with+stationary+contours.">The furrow illusion: Peripheral motion becomes aligned with stationary contours.</a> J. of Vis. 12, 1-11 (2012).</li><li>Ito, H., Yang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+short+line+segment+squirms+along+a+zigzag+line.">A short line segment squirms along a zigzag line.</a> i-Perc. 4, 141 (2013).</li><li>Ambadar, Z., Schooler, J. W., Cohn, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deciphering+the+Enigmatic+Face:+The+Importance+of+Facial+Dynamics+in+Interpreting+Subtle+Facial+Expressions.">Deciphering the Enigmatic Face: The Importance of Facial Dynamics in Interpreting Subtle Facial Expressions.</a> Am. Psych. Soc. 16 (5), 403-410 (2005).</li></ol>

The findings of the study conducted by Soranzo &#38; Newberry3 indicate that the ambiguity of the expression in Leonardo da Vinci&#39;s La Bella Principessa portrait is attributable to a visual illusion. A new mixed-methodology which combined three methods: Inter-observation, structured interviews, and psychophysical experiments was adopted. Firstly, the inter-observation method was used to shed some light on the &#39;ambiguity&#39; of the Princess&#39;s facial expression. This method which involves l...

This paper discusses the methodology used by Soranzo and Newberry3 to investigate the &#39;Uncatchable Smile&#39; illusion in Leonardo da Vinci&#39;s La Bella Principessa portrait. The overall goal of the methodology employed was to identify what makes the expression of the Princess ambiguous. The portrait shows the profile of a young woman identified as Bianca, the illegitimate daughter of Ludovico, who at around 13 years of age was to be married to a commander of the Duke&#39;s Milanese forces4. According to Kemp5, the portrait was commissioned by the Duke in honor of the celebration of her marriage in 1496. Kemp and Cotte6 noted that the expression of La Bella Principessa is ambiguous and &#34;subtle to an inexpressible degree&#34; (p.26), although the question remains as to what it is that triggers this ambiguity and whether this is similar to that perceived in Leonardo&#39;s Mona Lisa.
Soranzo and Newberry&#39;s3 study involved three stages which combined three different research methods. The rationale for using these different research methods was to conduct a research investigation that developed without prior beliefs, thus minimizing potential researcher bias. The first stage used the inter-observation method to investigate why the expression of the Princess is ambiguous; in the second, a structured interview was used to identify the psychological dimension underpinning the &#39;Uncatchable Smile&#39; illusion; and in the third stage experiments were conducted to test hypotheses formulated on the basis of the findings of the first two stages. Independent groups of participants took part in these three stages and the findings of each stage influenced the following stages. This is likely to have reduced researcher bias compared to if the researchers had determined the research questions themselves.
The advantages of combining different research methods over singular methods are as follows. First, the inter-observation stage enabled discussion to take place about where the ambiguity may have originated from (rather than the researchers imposing their own pre-determined view). Second, the interview stage enabled the identification of the psychological dimension to be investigated without imposing pre-defined categories. Third, the experimental stage enabled the perceptual change identified in the previous stages to be quantified in a controlled manner.
Inter-observation
As noted above, La Bella Principessa&#39;s expression is &#34;subtle to an inexpressible degree&#34;6. The first step of the research was to try to identify what it is about the portrait that makes the expression ambiguous. To do this, the inter-observation method posited by Paolo Bozzi and his colleagues7, 8 was conducted with three participants and the senior author. This method enables maximum information to be extracted from direct experience9 and involves looking together, discussing and mutually exchanging views. The first step of the research adhered to the guidelines provided by Bozzi who argued that observers should conjointly partake in the observational process in a natural environment (not in a laboratory); observers should be aware of the researcher&#39;s hypothesis (no hidden hypothesis); the instructions to participants should be broad and discussed together rather than providing strict instructions; the discussion should go beyond the first impression (for a discussion of the un-permeability of this method in relation to the so called &#34;conformity effect&#34; found by Asch11 see Bozzi7). According to Bozzi, the discussion should go beyond the first impression in order to explore all possible solutions. The conclusion is therefore reached through a process of &#34;negotiation&#34; between the participants and the researcher, and negotiation is the process through which a common account is determined10. Participants were presented with a copy of La Bella Principessa&#39;s portrait resting on an easel in diffuse lightning. General instructions were given; participants were requested to discuss the ambiguous expression of La Bella Principessa. In the negotiation stage, it became clear early on that the ambiguity in the Princess&#39;s expression, or the allure of the portrait, is triggered by a perceptual change. The Princess&#39;s expression is ambiguous because it is unstable; sometimes she looks happy and cheerful whilst at other times she looks melancholic and hostile. However, the conditions under which this change occurs were still not known. Further inspection and negotiation led to the unanimous conclusion that the change relates to the way the portrait is viewed: the Princess&#39;s expression appears to change when she is viewed from different distances. When the Princess is viewed from far away her mouth appears to take an upward direction, making her appear friendly and positive, but as soon as the portrait is approached, the Princess&#39;s mouth appears to take a downwards slant, making her look sad and unapproachable. In other words, it seems that the ambiguity in the Princess&#39;s expression is due to a visual illusion of direction, which depends on the viewing distance. Since spatial frequency changes with distance it was concluded that this change relates to spatial frequency.
The existence of a spatial frequency-dependent illusion of direction was also explored by using a blurred digital version of the portrait. A digital version of La Bella Principessa was presented on a computer screen and the level of blur was manipulated. The blurring process was essentially a convolution kernel of the pixel spreading type in which pixels take contributions from their surrounding pixels, while de-emphasizing contributions from the center12. In addition to appearing more cheerful and happy when viewed from a distance, La Bella Principessa also appeared more cheerful and happy when viewed as a blurred image. This supports the idea of a spatial frequency-dependent illusion. The concept of spatial frequency-dependent facial expression is supported by a wide understanding of how the human visual system is particularly sensitive to seeing and interpreting the subtleties of facial expression13, 14.
Structured Interviews
The results of the inter-observation stage led us to hypothesize that the Princess&#39;s expression is ambiguous because it is unstable and that this instability may be attributable to a spatial frequency-dependent perceptual change relating to the direction of the mouth. The assumption was that if there is a &#39;perceptual change&#39; which relates to the way the portrait is viewed, then there must be a controllable way to elicit one impression in the viewer over another (for example, the melancholic one rather than the cheerful one). The challenge was to find out how to control the viewer&#39;s impression of La Bella Principessa in order to generate one impression over the other. Before addressing this problem in a quantitative manner, structured interviews were conducted to determine the psychological dimension that best captures this perceptual change.
Four participants who had not taken part in the inter-observational stage of the study took part in a structured interview. Participants were shown an identical copy of La Bella Principessa&#39;s portrait resting on an easel in diffuse lighting. Participants were asked to describe the Princess&#39;s expression and to note any differences in the expression when viewed from close or further away. Interestingly, participants&#39; descriptions were not framed in terms of outward expressions such as &#39;smiling&#39; but more with the internal emotional state of the Princess. A Grounded Theory analysis15,16,17,18 of the descriptions was conducted and it was found that the most common words used to describe the Princess&#39;s expression were &#34;happiness&#34; and &#34;contentment&#34;. These findings suggested that the change in the Princess&#39;s expression might be better captured with the definition of a change in perceived &#34;contentment&#34;. Together, the inter-observational and structured interview stages informed the formulation of five hypotheses as follows: First, the viewer&#39;s distance from La Bella Principessa&#39;s portrait will influence their perception of her facial expression. Specifically, the ratings of contentment will be higher when the portraits are viewed from further away. Second, the portrait&#39;s level of blur will influence the perceived contentment of La Bella Principessa. Specifically, presenting digital versions of the portrait with an increased level of blur will lead to an increase in the viewer&#39;s perception of contentment. Third, the uncatchable smile illusion is mainly attributable to the mouth area of La Bella Principessa&#39;s portrait. Fourth, the perceived slant of La Bella Principessa&#39;s mouth will change when the distance of the portrait is manipulated. Specifically, the corner of the mouth will appear to take an upward turn when distance is increased. Fifth, the perceived slant of La Bella Principessa&#39;s mouth will change when a digital version of the portrait is presented with different levels of blur. Specifically, the corner of the mouth will appear to take an upward turn when the level of blur is increased.
Psychophysical Experiments
In the quantitative stage of the study, five psychophysical experiments were conducted to test the aforementioned hypotheses. In addition, since it was hypothesized that a similar effect would be observed for the Mona Lisa&#39;s expression, this portrait was also included in the investigation. Furthermore, to test whether the effect under investigation is specific to La Bella Principessa and the Mona Lisa or whether it may be general to all portraits of Leonardo&#39;s era, a control portrait was also used. This was the Portrait of a Girl painted around 1470 by Piero del Pollaiuolo. This was chosen as a suitable control for La Bella Principessa as the portrait is from the same period and there are similarities of size, presentation and appearance in the subject matter.

<table border="0" cellpadding="0" cellspacing="0" width="1531">
	<tbody>
		<tr height="19">
			<td height="19" style="height:19px;width:841px;">High quality same size reproductions of the following three portraits: The Mona Lisa and La Bella Principessa (Leonardo da Vinci) and Portrait of a Girl (Piero del Pollaiuolo)</td>
			<td style="width:691px;">The Print Shop - Sheffield Hallam University - Sheffield Hallam University, Howard Street, Sheffield, South Yorkshire S1 1WB, United Kingdom</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Easel for resting portraits on</td>
			<td>No particular brand needed</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Laptop computer with wireless mouse for experiments</td>
			<td>Lenovo</td>
		</tr>
		<tr height="20">
			<td height="40" rowspan="2" style="height:40px;">Programming software to write syntax to present the pictures in random order, record participant responses from the keyboard, and enable the measurement &#39;handle&#39; to be adjusted by participants</td>
			<td rowspan="2">True Basic software</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Image editing software</td>
			<td>Adobe Photoshop CC 2015</td>
		</tr>
	</tbody>
</table>

investigating the 'uncatchable smile' in leonardo da vinci's la bella principessa: a comparison with the mona lisa and pollaiuolo's portrait of a girl

This paper discusses how the &#39;Uncatchable Smile&#39; illusion in Leonardo da Vinci&#39;s La Bella Principessa portrait was discovered. Kemp and Cotte1 described the expression of the Princess as ambiguous and &#34;subtle to an inexpressible degree&#34;. A combination of three methods was used (inter-observation, structured interviews, and psychophysical experiments) to identify what may underlie this &#39;ambiguity&#39;. The inter-observation and the structured interview methods were firstly applied to generate experimental hypotheses that were successively tested by a series of psychophysical experiments. The combination of these research methods minimizes the impact of the researcher&#39;s beliefs and biases in the development of the research design. It emerged that the ambiguity in La Bella Principessa is triggered by a change in the perceived level of contentment in her facial expression and that this perceptual change is attributable to a visual illusion relating to her mouth. Moreover, it was found that a similar effect can be observed in the Mona Lisa. As the smile in La Bella Principessa disappears as soon as the viewer tries to &#39;catch it&#39;, we named this visual illusion the &#39;Uncatchable Smile&#39;. The elusive quality of the Mona Lisa&#39;s smile2 is probably why the portrait is so famous, and so the existence of a similar ambiguity in a portrait painted by Leonardo prior to the Mona Lisa is even more interesting.

From the negotiation process of the Inter-observation stage it was ascertained that the ambiguity in the Princess&#39;s expression might be due to a visual illusion of direction which depends on the viewing distance. Since spatial frequency changes with distance it was concluded that this change relates to spatial frequency. A Grounded Theory analysis of the descriptions obtained in the Structured Interview stage was performed and it was found that observers tended to describe her change ...

Watch this Scientific Journal Video about Investigating the 'Uncatchable Smile' in Leonardo da Vinci's La Bella Principessa: A Comparison with the Mona Lisa and Pollaiuolo's Portrait of a Girl at JoVE

Investigating the &#039;Uncatchable Smile&#039; in Leonardo da Vinci&#039;s La Bella Principessa: A Comparison with the Mona Lisa and Pollaiuolo&#039;s Portrait of a Girl

This paper discusses the methodology used to reveal the &#39;Uncatchable Smile&#39; illusion in Leonardo da Vinci&#39;s La Bella Principessa portrait. A combination of three methods was used (inter-observation, structured interviews, and psychophysical experiments), which led to an investigation that shaped itself without prior beliefs, thus reducing potential researcher bias.

Investigating the 'Uncatchable Smile' in Leonardo da Vinci's La Bella Principessa: A Comparison with the Mona Lisa and Pollaiuolo's Portrait of a Girl

This paper discusses how the &#39;Uncatchable Smile&#39; illusion in Leonardo da Vinci&#39;s La Bella Principessa portrait was discovered. Kemp and Cotte1 ...

The overall goal of this experiment is to investigate the uncatchable smile in Leonardo da Vinci's La Bella Principessa and compare it with the Mona Lisa and a control portrait. This method of investigating multiple attributes can help identify what creates the ambiguity in the expression of La Bella Principessa and the Mona Lisa. The main advantage of using different research methods was to conduct a research investigation that developed without prior beliefs, thus minimizing potential research bias.In a well-lit room, begin by displaying La Bella Principessa's portrait in the center of an A1 paper pad that is resting on an easel. Ask the participant to describe the woman's expression and to note any differences in the participant's response as they view the portrait from close-up and from far away. Have the participant write down their observations on paper.To begin, place two markers on the floor in front of the easel, one 0.5 meters from the portrait for the close-up condition and the other eight meters from the portrait for the far condition. Depending on the experimental condition, display exact sized foam-backed digital copies of La Bella Principessa, the Mona Lisa, or the Portrait of a Girl at the center of an AI paper pad resting on the easel 1.80 meters from the floor. Ensure that the easel is placed under diffused lighting at the end of a long hallway with two doors that are 0.5 and eight meters from the portrait, respectively.Then cover the portrait with a sheet. As an extra precaution, for a participant assigned to the far condition, have them enter the corridor from the furthest door and stop at the marker furthest away from the portrait that they have been assigned to. Likewise, for a participant in the close condition, have them enter the corridor from the closest door and stop at the market closest to the portrait that they have been assigned to.Once the participant is at the marker, unveil the portrait and ensure that they are only able to see the portrait from the assigned marker. Finally, ask the participant to verbally rate the perceived contentment in the expression of the woman viewed in the assigned portrait on a scale of one to seven. Record the participant's response.Begin by creating a set of digital images for each of the three portraits with increasing levels of Gaussian blur in steps of one pixel per image. Next, seat a participant 50 centimeters away from either a normal computer monitor or a large screen, as in this case, in a well-illuminated room. Ask the participant to use the numeric keyboard to rate the perceived contentment in the expression of La Bella Principessa, Mona Lisa and the figure in Portrait of a Girl from one to seven.In order to establish the source of the illusory effect, use the same digital images of La Bella Principessa with different levels of Gaussian blur to create masked images. To do this, create a solid black rectangle mask of 0.3 by 0.6 centimeters and place it either over the mouth, over the eyes, or over both the mouth and eyes of the portrait. Finally, ask the participant to rate the perceived contentment of these masked La Bella Principessa images on a scale of one to seven.In a large room with diffused lighting, use a projector connected to a computer to display an exact sized digital version of La Bella Principessa onto a screen 1.80 meters from the floor. Place a wireless keyboard on top of the table 0.5 meters from the computer screen for the close condition and eight meters away from the screen for the far condition. Next, use programming software, to create a 0.9 centimeter long black hairline measurement handle on the computer screen.Place the hairline handle at the same level and four centimeters left of the mouth. Instruct the participant to use the minus and plus keys on the numeric keyboard to adjust the slant of the handle until it aligns with the perceived slant of the mouth of the woman in the portrait. Press the space bar to record the perceived mouth slant angle.For the final experiment, present eight versions of La Bella Principessa with different levels of blur in a random order on the screen. Finally, have the participant adjust the slant of the handle on each of the blurred images until it aligns with the perceived slant of the woman's mouth in the portrait. When La Bella Principessa and Mona Lisa were observed from a distance, their perceived contentment was significantly higher than when the portraits were viewed from close-up, whereas, there was no significant effect for Pollaiuolo's Portrait of a Girl.The level of blur affected the perceived contentment of La Bella Principessa and Mona Lisa, but did not affect Pollaiuolo's Portrait. Furthermore, the perceived contentment of La Bella Principessa increased with the level of blur in both the no mask and eye mask conditions. Finally, the perceived mouth slant of La Bella Principessa was perceived to take an upward slant when viewed from far away, but it was perceived to take a downward direction when observed from close-up.After watching this video, you should have a good understanding of how to investigate how the pieces eliciting ambiguous emotions through the combined use of three methods;inter-observations, structured interviews, and psycho-physical experiments. While attempting this procedure, it's important to remember to recruit different participants for each of the three different stages of this method. While in the inter-observation stage, participant can be familiar with the stimuli, it is important that participants in the experimental stage are naive to the hypotheses.After its development, this technique paved the way for researchers in art perception to explore different pieces of art.

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6.8K vistas.  Sheffield Hallam University. The overall goal of this experiment is to investigate the uncatchable smile in Leonardo da Vinci's La Bella Principessa and compare it with the Mona Lisa and a control portrait. This method of investigating multiple attributes can help identify what creates the ambiguity in the expression of La Bella Principessa and the Mona Lisa. The main advantage of using different research methods was to conduct a research investigation that developed without prior beliefs, thus minimizing potential resea...

Video: Investigating the 'Uncatchable Smile' in Leonardo da Vinci's La Bella Principessa: A Comparison with the Mona Lisa and Pollaiuolo's Portrait of a Girl