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

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.