Winand H. Dittrich

Emotion perception from dynamic and static body expressions in point-light and full-light displays.

Research on emotion recognition has been dominated by studies of photographs of facial expressions. A full understanding of emotion perception and its neural substrate will require investigations that employ dynamic displays and means of expression other than the face. Our aims were: (i) to develop a set of dynamic and static whole-body expressions of basic emotions for systematic investigations of clinical populations, and for use in functional-imaging studies; (ii) to assess forced-choice emotion-classification performance with these stimuli relative to the results of previous studies; and (iii) to test the hypotheses that more exaggerated whole-body movements would produce (a) more accurate emotion classification and (b) higher ratings of emotional intensity. Ten actors portrayed 5 emotions (anger, disgust, fear, happiness, and sadness) at 3 levels of exaggeration, with their faces covered. Two identical sets of 150 emotion portrayals (full-light and point-light) were created from the same digital footage, along with corresponding static images of the ‘peak’ of each emotion portrayal. Recognition tasks confirmed previous findings that basic emotions are readily identifiable from body movements, even when static form information is minimised by use of point-light displays, and that full-light and even point-light displays can convey identifiable emotions, though rather less efficiently than dynamic displays. Recognition success differed for individual emotions, corroborating earlier results about the importance of distinguishing differences in movement characteristics for different emotional expressions. The patterns of misclassifications were in keeping with earlier findings on emotional clustering. Exaggeration of body movement (a) enhanced recognition accuracy, especially for the dynamic point-light displays, but notably not for sadness, and (b) produced higher emotional-intensity ratings, regardless of lighting condition, for movies but to a lesser extent for stills, indicating that intensity judgments of body gestures rely more on movement (or form-from-movement) than static form information.

Imperfect mimicry: a pigeon’s perspective

Despite the dearth of field-based evidence from natural model-mimic communities, theory suggests that Batesian mimicry should have limits placed upon the model:mimic ratio for mimics to benefit. Paradoxically, hoverflies that are apparently mimics are often superabundant, many times more abundant than their supposed models. One possible solution to this paradox is that perhaps they are not mimics at all. We use discriminative operant conditioning methods to measure the similarity perceived by pigeons between wasps and various species of supposedly mimetic hoverflies, and an image processing technique to measure objective similarity. We demonstrate that pigeons rank mimics according to their similarity to a wasp model, in an orderly broadly similar to our own intuitive rankings. Thus pigeons behave as if many hoverflies are indeed wasp mimics. However, they rank the two commonest hoverflies as very similar to wasps, despite these looking decidedly poor mimics to the human eye. In these species, ‘poor’ mimicry may have been sustainable because it exploits some constraint in birds’ visual or learning mechanisms, or some key feature used in pattern recognition. Furthermore, the relation between similarity and mimicry is nonlinear: small changes in similarity can lead to dramatic increases in the degree of mimicry.

Evidence for Distinct Contributions of Form and Motion Information to the Recognition of Emotions from Body Gestures.

The importance of kinematics in emotion perception from body movement has been widely demonstrated. Evidence also suggests that the perception of biological motion relies to some extent on information about spatial and spatiotemporal form, yet the contribution of such form-related cues to emotion perception remains unclear. This study reports, for the first time, the relative effects on emotion recognition of inverting and motion-reversing patch-light compared to fully illuminated displays of whole-body emotion gestures. Inverting the gesture movies or playing them backwards significantly impaired emotion classification accuracy, but did so more for patch-light displays than for identical but fully illuminated movement sequences. This result suggests that inversion impairs the processing of form information related to the configuration of body parts, and reversal impairs the sequencing of form changes, more than these manipulations impair the processing of kinematic cues. This effect was strongest for inversion, suggesting an important role for configural information in emotion recognition. Nevertheless, even in combination these stimulus manipulations did not abolish above chance recognition of any of the emotions, suggesting that kinematics help distinguish emotions expressed by body gestures. Disproportionate impairments in recognition accuracy were observed for fear and disgust under inversion, and for fear under motion reversal, suggesting a greater role for form-related cues in the perception of these emotions.

Eye movements and spatial working memory in Parkinson's disease.

Abstract Mechanisms of spatial working memory and eye movement control were investigatedin eight mild to moderate Parkinsons disease patients (PDs). Subjects were presented with asequence of four targets which had to be memorized and then recalled by moving their eyes tofixate the four locations in the correct order. Two variations on this procedure were used inwhich either a different sequence of lights was presented on each trial, or an identical sequenceof lights was repeated on each trial. In both conditions subjects made memory-guided eyemovements in the dark, without any visual cues to eye movement accuracy or the locations of thepreviously illuminated lights. Analysis of the amplitude of the primary eye movement and finaleye position for each step in the sequence showed that PDs made several discrete saccadic eyemovements of reduced amplitude before reaching the final eye position (multi-stepping). When anovel target sequence had to be memorized on each trial, the final eye position reached by PDsfor each location was also found to undershoot relative to controls. In contrast, when an identicalsequence of targets was repeated on each trial, PDs final eye position was found to be normal,although primary movement amplitudes were still reduced. PDs showed no multi-stepping andnormal final eye position gain under conditions for which the target lights in the sequence wereilluminated during movement execution. PDs also made an increased proportion of overt errorsin target sequence recall. Parallel neuropsychological testing in PDs and controls revealed thaterror rates in the sequential memory-guided saccade task were significantly correlated withperformance in a task thought to be sensitive to spatial working memory dysfunction. Thefindings suggest that short-term spatial memory representations are disrupted in the early stagesof PD.

Cognitive deficits of executive functions and decision-making in obsessive-compulsive disorder

The nature of cognitive deficits in obsessive-compulsive disorder (OCD) is characterized by contradictory findings in terms of specific neuropsychological deficits. Selective impairments have been suggested to involve visuospatial memory, set shifting, decision-making and response inhibition. The aim of this study was to investigate cognitive deficits in decision-making and executive functioning in OCD. It was hypothesized that the OCD patients would be less accurate in their responses compared to the healthy controls in rational decision-making on a version of the Cambridge gambling task (CGT) and on the color-word interference test and on a version of the Tower of Hanoi test (tower test) of executive functioning. Thirteen participants with OCD were compared to a group of healthy controls (n = 13) matched for age, gender, education and verbal IQ. Results revealed significant differences between the OCD group and the healthy control group on quality of decision-making on the CGT and for achievement score on the tower test. On these two tasks the OCD group performed worse than the healthy control group. The symptom-dimension analysis revealed performance differences where safety checking patients were impaired on the tower test compared to contamination patients. Results are discussed in the framework of cognition and emotion processing and findings implicate that OCD models should address, specifically, the interaction between cognition and emotion. Here the emotional disruption hypothesis is forwarded to account for the dysfunctional behaviors in OCD. Further implications regarding methodological and inhibitory factors affecting cognitive information processing are highlighted.

Conditioning pigeons to discriminate naturally lit insect specimens.

Pigeons (Columba livia) were trained on a visual discrimination task using a novel apparatus which enabled pinned specimens of insects, illuminated by natural daylight, to be presented under a pecking key transparent to ultraviolet light. Three birds showed evidence of learning to discriminate between sets of wasp and fly specimens. This response transferred to specimens of four hoverfly species, the strength of the response varying between the different hoverfly species. This conditioning technique offers a promising means of analysing mechanisms of visual processing in birds that are relevant to theories of the evolution of camouflage and mimicry.

Disgust and fear recognition in paraneoplastic limbic encephalitis

Paraneoplastic limbic encephalitis (PNLE) affects limbic portions of the brain associated with recognition of social signals of emotions. Yet it is not known whether this perceptual ability is impaired in individuals with PNLE. We therefore conducted a single case study to explore possible impairments in recognising facially, vocally and bodily expressed emotions, using standardised emotion recognition tests. Facial expression recognition was tested with two forced-choice emotion-labelling tasks using static faces with either prototypical or morphed blends of basic emotions. Recognition of vocally and bodily expressed emotions was also tested with forced-choice labelling tasks, one based on prosodic cues, the other on whole-body movement cues. We found a deficit in fear and disgust recognition from both face and voice, while recognition of bodily expressed emotions was unaffected. These findings are consistent with data from previous studies demonstrating critical roles for certain brain regions - particularly the amygdala and insular cortex - in processing facially and vocally displayed basic emotions, and furthermore, suggest that recognition of bodily expressed emotions may not depend on neural structures involved in facial and vocal emotion recognition. Impaired facial and vocal emotion recognition may form a further neuropsychological marker of limbic encephalitis, in addition to the already well-described mnestic deficits.

Cognitive Performance in a Subclinical Obsessive-Compulsive Sample 1: Cognitive Functions

Individuals who are not clinically diagnosed with obsessive-compulsive disorder (OCD) but still display obsessive-compulsive (OC) tendencies may show cognitive impairments. The present study investigated whether there are subgroups within a healthy group showing characteristic cognitive and emotional performance levels similar to those found in OCD patients and whether they differ from OCD subgroups regarding performance levels. Of interest are those cases showing subclinical symptomatology. The results revealed no impairments in the subclinical OC participants on the neuropsychological tasks, while evidence suggests that there exist high and low scores on two standardised clinical instruments (Yale-Brown Obsessive Compulsive Scale and Cognitive Assessment Instrument of Obsessions and Compulsions) in a healthy sample. OC symptoms may diminish the quality of life and prolong sustainable return to work. It may be that occupational rehabilitation programmes are more effective in rectifying subclinical OC tendencies compared to the often complex symptoms of diagnosed OCD patients. The relationship between cognitive style and subclinical OC symptoms is discussed in terms of how materials and information might be processed. Although subclinical OC tendencies would not seem to constitute a diagnosis of OCD, the quality of treatment programmes such as cognitive behavioural therapy can be improved based on the current investigation.

Pointing and the interference effect in obsessive-compulsive disorder (OCD)

The interference effect in obsessive-compulsive disorder (OCD) was investigated in order to analyze cognitive aspects of motor stereotypy in OCD-related compulsions. So far, the domain of cognitive control in compulsive behavior has been under-investigated. Twelve participants (OCD patients and healthy controls) completed a newly created computer-based pointing task as well as standard clinical and psychological background measures. Findings showed that the patients displayed a larger visual interference effect compared to the controls and pointing paths were longer in time as well as distance when a distractor stimulus was present. It is concluded that, for compensation, patients would need to generate excessive amounts of attentional resources not available to overcome motor rigidity on the one side and visual distraction on the other side.

The Perception of Bodily Expressions of Emotion and the Implications for Computing

Increasingly rapid technological developments in robotics, human-computer interaction (HCI), and the computer and video games industry have led to the development of quite sophisticated, intelligent robots and realistic, computer-generated characters. These robots and characters vary in their human-like qualities, from visual and behavioural replicas of humans, to androids, aliens or other beings that have some human characteristics, to creatures that have little in common with humans. The most common human-like qualities evidenced by these robots and characters are intelligence, looks, movements and language. Yet until very recently they were often not endowed with much in the way of emotions, and when they were they typically appeared emotionally underdeveloped, stilted, or false. For example, in James Cameron’s film Terminator 2, Arnold Schwarzenegger plays an emotionless but intelligent humanoid robot. The film character explains that it is equipped with a microchip based on connectionist neural-net architecture. He comes to understand the patterning of human emotional behaviour but, of course, he does not have feelings or emotions. This was also true of other animated or computer-generated characters in films. Even if the characters gave rise to highly emotional video game or film scenes, the users or audience were in agreement that the characters were emotionally impoverished or did not have emotions at all. In large part this was and still is a technological issue: advances made in endowing machines and computer-generated characters with realistic emotions have not kept pace with the rapid advances in endowing such machines and characters with realistic intelligence, looks, movements and language. Nonetheless, given that these robots and characters are designed to interact with humans, and that emotions are so central to successful social interactions, effective implementation of emotions in these robots and characters is vital. The latest developments in HCI include an area that is concerned with implementing emotions with mostly human-like characteristics into HCI technology. About 10 years ago, even a completely new field of computer science emerged that is based on such an attempt, namely “affective computing” (Picard, 1997). Since then, various attempts have been made either to implement emotions into machines or have machines that express emotional reactions. A close examination of these examples reveals two ways of implementing emotions and emotional reactions in HCI technology. First, emotions are seen as