Refine
Document Type
- Doctoral Thesis (2)
Language
- English (2)
Has Fulltext
- yes (2)
Keywords
- Affekt (1)
- Anura (1)
- Emotion (1)
- Extraversion (1)
- Gehirn (1)
- NMR-Spektroskopie (1)
- Positive affect (1)
- Positiver Affekt (1)
- arterial spin labeling (1)
- cerebral blood flow (1)
Institute
- Psychologie (1)
There is ample evidence that the personality trait of extraversion is associated with frequent experiences of positive affect whereas introversion is associated with less frequent experiences of positive affect. According to a theory of Watson et al. (1997), these findings demonstrate that positive affect forms the conceptual core of extraversion. In contrast, several other researchers consider sociability - and not positive affect - as the core of extraversion. The aim of the present work is to examine the relation between extraversion and dispositional positive affect on the neurobiological level. In 38 participants resting cerebral blood flow was measured with continuous arterial spin labeling (CASL). Each participant was scanned on two measurement occasions separated by seven weeks. In addition, questionnaire measures of extraversion and dispositional positive affect were collected. To employ CASL for investigating the biological basis of personality traits, the psychometric properties of CASL blood flow measurements were examined in two studies. The first study was conducted to validate the CASL technique. Using a visual stimulation paradigm, the expected pattern of activity was found, i.e. there were specific differences in blood flow in the primary and secondary visual areas. Moreover, the results in the first measurement occasion could be reproduced in the second. Thus, these results suggest that CASL blood flow measurements have a high degree of validity. The aim of the second psychometric study was to examine whether resting blood flow measurements are characterized by a sufficient trait stability to be used as a marker for personality traits. Employing the latent state-trait theory developed by Steyer and colleagues, it was shown that about 70 % of the variance of regional blood flow could be explained by individual differences in a latent trait. This suggests that blood flow measurements have sufficient trait stability for investigating the biological basis of personality traits. In the third study, the relation between extraversion and dispositional positive affect was investigated on the neurobiological level. Voxel-based analyses showed that dispositional positive affect was correlated with resting blood flow in the ventral striatum, i.e. a brain structure that is associated with approach behavior and reward processing. This biological basis was also found for extraversion. In addition, when extraversion was statistically controlled, the association between dispositional positive affect and blood flow in the ventral striatum was still present. However, when dispositional positive affect was statistically controlled, the relation between extraversion and the ventral striatum disappeared. Taken together, these results suggest that positive affect forms a core of extraversion on the neurobiological level. The present findings thus add psychophysiological evidence to the theory of Watson et al. (1997), which suggests that positive affect forms the conceptual core of extraversion.
This thesis seeks to improve the understanding of evolution and habitat as key factors forming tadpole morphology (i.e. of larvae of the order Anura), uncovers existing gaps in current research and recommends strategies and directions for future research. The present study improves the knowledge about the influences of evolution and habitat on the bauplan of tadpoles in a global scale ensuring maximum standardization and comparability of the data. In relation to the total number of tadpoles assumed to exist, only a small proportion has been described and only a few of them have been identified genetically. The lack of a global standard for their description makes it difficult to compare data. Using the tadpole of a harlequin frog (Atelopus) from Guiana region, it is shown that only an integrative approach with morphological and genetic data can solve taxonomic problems. In the study area of Madagascar, it becomes evident that in this region the common genetic history only has little influence on morphology, in contrast to the aquatic way of life. Tadpoles from flowing waters develop larger eyes, more robust tail muscles and smaller fins to cope better with current conditions and move more efficiently. In an additional study, the examination is extended to an almost global level. To achieve the intended standardization, over 1000 individuals (tadpoles) from 144 species have been examined. It can be shown that the common evolutionary history on a global scale influences morphology as strongly as the habitat. In addition, the influence of specialized nutrition and the climate is investigated.
