The ability to communicate is one of the core aspects of human life. For this, we use not only verbal but also nonverbal signals of remarkable complexity. Among the latter, facial expressions belong to the most important information channels. Despite the large variety of facial expressions we use in daily life, research on facial expressions has so far mostly focused on the emotional aspect. Consequently, most databases of facial expressions available to the research community also include only emotional expressions, neglecting the largely unexplored aspect of conversational expressions. To fill this gap, we present the MPI facial expression database, which contains a large variety of natural emotional and conversational expressions. The database contains 55 different facial expressions performed by 19 German participants. Expressions were elicited with the help of a method-acting protocol, which guarantees both well-defined and natural facial expressions. The method-acting protocol was based on every-day scenarios, which are used to define the necessary context information for each expression. All facial expressions are available in three repetitions, in two intensities, as well as from three different camera angles. A detailed frame annotation is provided, from which a dynamic and a static version of the database have been created. In addition to describing the database in detail, we also present the results of an experiment with two conditions that serve to validate the context scenarios as well as the naturalness and recognizability of the video sequences. Our results provide clear evidence that conversational expressions can be recognized surprisingly well from visual information alone. The MPI facial expression database will enable researchers from different research fields (including the perceptual and cognitive sciences, but also affective computing, as well as computer vision) to investigate the processing of a wider range of natural facial expressions.

When observing art the viewer's understanding results from the interplay between the marks made on the surface by the artist and the viewer's perception and knowledge of it. Here we use a novel set of stimuli to dissociate the influences of the marks on the surface and the viewer's perceptual experience upon the manner in which the viewer inspects art. Our stimuli provide the opportunity to study situations in which (1) the same visual stimulus can give rise to two different perceptual experiences in the viewer, and (2) the visual stimuli differ but give rise to the same perceptual experience in the viewer. We find that oculomotor behaviour changes when the perceptual experience changes. Oculomotor behaviour also differs when the viewer's perceptual experience is the same but the visual stimulus is different. The methodology used and insights gained from this study offer a first step toward an experimental exploration of the relative influences of the artist's creation and viewer's perception when viewing art and also toward a better understanding of the principles of composition in portraiture.

The question of how humans perceive art and how the sensory percept is endowed with aesthetics by the human brain has continued to fascinate psychologists and artists alike. It seems, for example, rather easy for us to classify a work of art as either "abstract" or "representational". The artist Robert Pepperell recently has produced a series of paintings that seek to defy this classification: his goal was to convey "indeterminancy" in these paintings -scenes that at first glance look like they contain an object or belong to a certain genre but that upon closer examination escape a definite determination of their contents. Here, we report results from several psychophysical experiments using these artworks as stimuli, which seek to shed light on the perceptual processing of the degree of abstraction in images. More specifically, the task in these experiments was to categorize a briefly shown image as "abstract" or "representational". Stimuli included Pepperell's paintings each of which was paired with a similar representational work of art from several periods and several artistic genres. The results provide insights into the visual processes determining our perception of art and can also function as a "objective" validation for the intentions of the artist.

When observing art the viewer's understanding results from the interplay between the marks made on the surface by the artist and the viewer's perception and knowledge of it. Here we use a novel set of stimuli to dissociate the influences of the marks on the surface and the viewer's perceptual experience upon the manner in which the viewer inspects art. Our stimuli provide the opportunity to study situations in which (1) the same visual stimulus can give rise to two different perceptual experiences in the viewer, and (2) the visual stimuli differ but give rise to the same perceptual experience in the viewer. We find that oculomotor behaviour changes when the perceptual experience changes. Oculomotor behaviour also differs when the viewer's perceptual experience is the same but the visual stimulus is different. The methodology used and insights gained from this study offer a first step toward an experimental exploration of the relative influences of the artist's creation and viewer's perception when viewing art and also toward a better understanding of the principles of composition in portraiture.

How do we interpret an object -a scene -a painting? Perception research and art illuminate from different angles how the vast amount of information in our visually perceived environment is processed by the viewer to form a coherent and consistent interpretation of the world. Using drawings and paintings by the artist Robert Pepperell, this work attempts to connect these different world views. Pepperell's paintings at first glance seem to be a baroque fresco, an expressionist still-life, or a cubist collage; taking a closer look, however, this concrete interpretation vanishes and we are left with an indeterminate painting. Using psychophysical experiments and eyetracking measures, in this work we seek to illuminate the visual processing of information in Pepperell's paintings. More specifically, we will investigate how the pattern of fixations -the loci of interest -change as a function of the task ('What is depicted in this scene?' vs. 'Does this image contain people?') and of the image content. The interpretation of the experimental results in the context of perceptual research will give first insights into the perception of (indeterminate) art. Conversely, the results are also relevant for art, as they provide a kind of perceptual, measurable 'validation' of the artist's intentions.