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Cognition refers to the ability to of animals to acquire, process, store and use vital information from the environment. Cognitive processes are necessary to predict the future and reduce the uncertainty of the ever-changing environment. Classically, research on animal cognition focuses on decisive cognitive tests to determine the capacity of a species by the testing the ability of a few individuals. This approach views variability between these tested key individuals as unwanted noise and is thus often neglected. However, inter-individual variability provides important insights to behavioral plasticity, cognitive specialization and brain modularity. Honey bees Apis mellifera are a robust and traditional model for the study of learning, memory and cognition due to their impressive capabilities and rich behavioral repertoire. In this thesis I have applied a novel view on the learning abilities of honey bees by looking explicitly at individual differences in a variety of learning tasks. Are some individual bees consistently smarter than some of her sisters? If so, will a smart individual always perform good independent of the time, the context and the cognitive requirements or do bees show distinct isolated ‘cognitive modules’?
My thesis presents the first comprehensive investigation of consistent individual differences in the cognitive abilities of honey bees. To speak of an individual as behaving consistently, a crucial step is to test the individual multiple times to examine the repeatability of a behavior. I show that free-flying bees remain consistent in a visual discrimination task for three consecutive days. Successively, I explored individual consistency in cognitive proficiency across tasks involving different sensory modalities, contexts and cognitive requirements. I found that free-flying bees show a cognitive specialization between visual and olfactory learning but remained consistent across a simple discrimination task and a complex concept learning task. I wished to further explore individual consistency with respect to tasks of different cognitive complexity, a question that has never been tackled before in an insect. I thus performed a series of four experiments using either visual or olfactory stimuli and a different training context (free-flying and restrained) and tested bees in a discrimination task, reversal learning and negative patterning. Intriguingly, across all these experiments I evidenced the same results: The bees’ performances were consistent across the discrimination task and reversal learning and negative patterning respectively. No association was evidenced between reversal learning and negative patterning. After establishing the existence of consistent individual differences in the cognitive proficiency of honey bees I wished to determine factors which could underlie these differences. Since genetic components are known to underlie inter-individual variability in learning abilities, I studied the effects of genetics on consistency in cognitive proficiency by contrasting bees originating from either from a hive with a single patriline (low genetic diversity) or with multiple patrilines (high genetic diversity). These two groups of bees showed differences in the patterns of individually correlated performances, indicating a genetic component accounts for consistent cognitive individuality. Another major factor underlying variability in learning performances is the individual responsiveness to sucrose solution and to visual stimuli, as evidenced by many studies on restrained bees showing a positive correlation between responsiveness to task relevant stimuli and learning performances. I thus tested whether these relationships between sucrose/visual responsiveness and learning performances are applicable for free-flying bees. Free-flying bees were again subjected to reversal learning and negative patterning and subsequently tested in the laboratory for their responsiveness to sucrose and to light. There was no evidence of a positive relationship between sucrose/visual responsiveness and neither performances of free-flying bees in an elemental discrimination, reversal learning and negative patterning. These findings indicate that relationships established between responsiveness to task relevant stimuli and learning proficiency established in the laboratory with restrained bees might not hold true for a completely different behavioral context i.e. for free-flying bees in their natural environment.
These results show that the honey bee is an excellent insect model to study consistency in cognitive proficiency and to identify the underlying factors. I mainly discuss the results with respect to the question of brain modularity in insects and the adaptive significance of individuality in cognitive abilities for honey bee colonies. I also provide a proposition of research questions which tie in this theme of consistent cognitive proficiency and could provide fruitful areas for future research.
This dissertation explores the development and assessment of inhibitory control – a crucial component of executive functions – in young children. Inhibitory control, defined as the ability to suppress inappropriate responses (Verbruggen & Logan, 2008), is essential for adaptable and goal-oriented behavior. The rapid and non-linear development of this cognitive function in early childhood presents unique challenges for accurate assessment. As children age, they often exhibit a ceiling effect in terms of response accuracy (Petersen et al., 2016), underscoring the need to consider response latency as well. Ideally, combining response latency with accuracy could yield a more precise measure of inhibitory control (e.g., Magnus et al., 2019), facilitating a detailed tracking of developmental changes in inhibitory control across a wider age spectrum. The three studies of this dissertation collectively aim to clarify the relationship between response accuracy, response latency, and inhibitory control across different stages of child development. Each study utilizes a computerized Pointing Stroop Task (Berger et al., 2000) to measure inhibitory control, examining the task's validity and the integration of dual metrics for a more comprehensive evaluation.
The first study focuses on establishing the validity of using both response accuracy and latency as indicators of inhibitory control. Utilizing the framework of explanatory item-response modeling (De Boeck & Wilson, 2004), the study revealed how the task characteristics congruency and item position influence both the difficulty level and timing aspects in young children’s responses in the computerized Pointing Stroop task. Further, this study found that integrating response accuracy with latency, even in a basic manner, provides additional insights. Building upon these findings, the second study investigates the nuances of integrating response accuracy and latency, examining whether this approach can account for age-related differences in inhibitory control. It also explores whether response latencies may contain different information depending on the age and proficiency of the children. The study leverages novel and established methodological perspectives to integrate response accuracy and latency into a single metric, showing the potential applicability of different approaches for assessing inhibitory control development. The third study extends the investigation to a longitudinal perspective, exploring the dynamic relationship between response accuracy, latency, and inhibitory control over time. It assesses whether children who achieve high accuracy at an earlier age show faster improvement in response latency, suggesting a non-linear maturation pathway of inhibitory control. The study also examines if the predictive value of early response latency for later fluid intelligence is dependent on the response accuracy level.
Together, these empirical studies contribute to a more robust understanding of the complex interaction between inhibitory control, response accuracy, and response latency, facilitating valid evaluations of cognitive capabilities in children. Moreover, the findings may have practical implications for designing educational strategies and clinical interventions that address the developmental trajectory of inhibitory control. The nuanced approach advocated in this dissertation suggests prioritizing accuracy in assessment and interventions during the early stages of children's cognitive development, gradually shifting the focus to response latency as children mature and secure their inhibitory control abilities.
Humans actively interact with the world through a wide range of body movements. To understand human cognition in its natural state, we need to incorporate ecologically relevant body movement into our account. One fundamental body movement during daily life is natural walking. Despite its ubiquity, the impact of natural walking on brain activity and cognition has remained a realm underexplored.
In electrophysiology, previous studies have shown a robust reduction of ongoing alpha power in the parieto-occipital cortex during body movements. However, what causes the reduction of ongoing alpha, namely whether this is due to body movement or prevalent sensory input changes, was unknown. To clarify this, study 1 was performed to test if the alpha reduction is dependent on visual input. I compared the resting state alpha power during natural walking and standing, in both light and darkness. The results showed that natural walking led to decreased alpha activity over the occipital cortex compared to standing, regardless of the lighting condition. This suggests that the movement-induced modulation of occipital alpha activity is not driven by visual input changes during walking. I argue that the observed alpha power reduction reflects a change in the state of the subject based on disinhibition induced by walking. Accordingly, natural walking might enhance visual processing and other cognitive processes that involve occipital cortical activity.
I first tested this hypothesis in vision. Study 2 was performed to examine the possible effects of natural walking across visual processing stages by assessing various neural markers during different movement states. The findings revealed an amplified early visual response, while a later visual response remain unaffected. A follow-up study 3 replicated the walking-induced enhancement of the early visual evoked potential and showed that the enhancement was dependent on specific stimulus-related parameters (eccentricity, laterality, distractor presence). Importantly, the results provided evidence that the enhanced early visual responses are indeed linked to the modulation of ongoing occipital alpha power. Walking also modulated the stimulus-induced alpha power. Specifically, it showed that when the target appeared in the fovea area without a distractor, walking exhibited a significantly reduced modulation of alpha power, and showed the largest difference to standing condition. This effect of eccentricity indicates that during later visual processing stages, the visual input in the fovea area is less processed than in peripheral areas while walking.
The two visual studies showed that walking leads to an enhancement in temporally early visual processes which can be predicted by the walking-induced change in ongoing alpha oscillation likely marking disinhibition. However, while walking affects neural markers of early sensory processes, it does not necessarily lead to a change in the behavioural outcome of a sensory task. The two visual studies suggested that the behavioural outcome seems to be mainly based on later processing stages.
To test the effects of walking outside the visual domain, I turned to audition in study 4. I investigated the influence of walking in a particular path vs. simply stepping on auditory processing. Specifically, the study tested whether enhanced processing due to natural walking can be found in primary auditory brain activity and whether the processing preferences are dependent on the walking path. In addition, I tested whether the changed spatial processing that was reported in previous visual studies can be seen in the auditory domain. The results showed enhanced sensory processing due to walking in the auditory domain, which was again linked to the modulation of occipital alpha oscillation. The auditory processing was further dependent on the walking path. Additionally, enhanced peripheral sensory processing, as found in vision, was also present in audition.
The findings outside vision supported the idea of natural walking affecting cognition in a rather general way. Therefore in my study 5, I examined the effect of natural walking on higher cognitive processing, namely divergent thinking, and its correlation with the modulation of ongoing alpha oscillation. I analyzed alpha oscillations and behavioural performance during restricted and unrestricted movement conditions while subjects completed a Guilford's alternate uses test. The results showed that natural walking, as well as missing body restriction, reduces the occipital alpha ongoing power independent of the task phase which goes along with higher test scores. The occipital alpha power reduction can therefore be an indicator of a changed state that allows improved higher cognitive processes.
In summary, the research presented in this thesis highlights that natural walking can change different processes in the visual and auditory domain as well as higher cognitive processes. The effect can be attributed to the movement of natural walking itself rather than to changes in sensory input during walking. The results further indicate that the walking-induced modulation of ongoing occipital alpha oscillations drives the cognitive effects. We therefore suggest that walking changes the inhibitory state which can influence awareness and attention. Such a mechanism could facilitate an adaptive enhancement in cognitive processes and thereby optimize movement-related behaviour such as navigation.
Im Rahmen dieser Dissertation wurde geprüft, welchen Verlauf die kognitiven Leistungen von Patienten nach der operativen Resektion eines intrakraniellen Meningeoms nahmen und ob hierbei Unterschiede zwischen den Personen bestanden, die eine anschließende Rehabilitation absolvierten, sowie jenen, die keine weiteren Maßnahmen erhielten.
Mit der ersten Hypothese wurde angenommen, dass Patienten ohne Rehabilitation drei Monate nach der Operation ihre kognitiven Fähigkeiten im Vergleich zu einer Woche nach dem Eingriff verbessern. Dies konnte nicht eindeutig bestätigt werden, da eine Steigerung der Leistungen in dieser Patientengruppe nur in fünf der sechzehn Teilgebiete erreicht wurde. Die zweite Hypothese basierte auf der Annahme, dass Patienten mit einer Rehabilitationsmaßnahme Leistungssteigerungen in den getesteten Gebieten zeigten. Der Vergleich fand eine Woche nach dem operativen Eingriff und drei Monate nach der Operation statt. Diese Hypothese kann durch die vorliegenden Ergebnisse im Rahmen der Konzentrationsleistung zumindest eingeschränkt bejaht werden. Es ließen sich zwei signifikante Unterschiede der Ergebnisse der Patienten mit anschließender Rehabilitation beobachten. Hier konnte im ergänzend zur ANOVA berechneten t-Test ein signifikanter Unterschied bei der Leistungssteigerung der Patienten mit anschließender Rehabilitation nachgewiesen werden. Des Weiteren kam es in dieser Patientengruppe zu gesteigerten Leistungen in vierzehn von sechzehn Teilgebieten. Im Falle der dritten Hypothese sollte exploriert werden, ob die Patientengruppe mit anschließender Rehabilitationsmaßnahme im Vergleich zur Patientengruppe ohne weitere Maßnahmen eine größere Leistungssteigerung erfuhr. Dabei konnte eine leichte Tendenz beobachtet werden. Es wurden Verbesserungen der Patientengruppe mit Rehabilitation gegenüber den Patienten ohne weitere Maßnahmen in neun von sechzehn Kategorien beobachtet. Somit lässt sich die Annahme stützen, dass eine postoperative Rehabilitationsmaßnahme sich positiv auf die kognitiven Leistungen bei Meningeom-Patienten auswirkt.
Humans spontaneously blink several times a minute. These blinks are strongly modulated during various cognitive task. However, the precise function of blinking and the reason for their modulation has not been fully understood. In the present work, I investigated the function of spontaneous blinks through various perceptual and cognitive tasks. Previous research has revealed that blinks rates decrease during some tasks but increase during others. When trying to understand these seemingly contradictory results, I observed that blink reduction occurs when one engages with an external input. For instance, a decrease has been observed due to the onset of a stimulus, sensory input processing and attention towards sensory input. However, for activities that do not involve such an engagement, e.g. imagination, daydreaming or creativity, the blink rate has been shown to increase. To follow up on the proposed hypothesis, I distinguished tasks that involve the processing of an external stimulus and tasks that involve disengagement.
In the first part of the project, I explored blinking during stimulus engagement. If the probability of blinking is low when engaging with the stimulus, then one should find a reduction in blinks specifically during the time period of processing but not during sensory input per se. To this end, in study 1, I tested the influence of task-relevant information duration on blink timing and additionally manipulated the overall sensory input using a visual and an auditory temporal simultaneity judgement task. The results showed that blinks were suppressed longer for longer periods of relevant information or in other words, blinks occurred at the end of relevant information processing for both the visual and the auditory modality. Since relevance is mediated through top-down processes, I argue that the reduction in blinks is a top-down driven suppression. In studies 2 and 3, I again investigated stimulus processing, but in this case, processing was triggered internally and not based on specific changes in the external input. To this end, I used bistable stimuli, in which the actual physical stimulus remains constant but their perception switches between different interpretations. Studies on the involvement of attention in such bistable perceptual changes indicate that the sensory input is reprocessed before the perceptual switch. The results revealed a reduction in eye blink rates before the report of perceptual switches. Importantly, I was able to decipher that the decrease was not caused by the perceptual switch or the behavioral response but likely started before the internal switch. Additionally, periods between a blink and a switch were longer than interblink intervals, indicating that blinks were followed by a period of stable percept. To conclude, the first part of the project revealed that there is a top-down driven blink suppression during the processing of an external stimulus.
In the second part of the project, I extended the idea of blinks marking the disengagement from external processing and tested if blinking is associated with better performance during internally directed processes. Specifically, I investigated divergent thinking, an aspect of creativity, and the link between performance and blink rates as well as the effect of motor restriction. While I could show that motor restriction was the main factor influencing divergent thinking, the relationship between eye blink rates and creative output also depended on restriction. Results showed that higher blink rates were associated with better performance during free movement, but only between subjects. In other words, subjects who had overall higher blink rates scored better in the task, but when they were allowed to sit or walk freely. Within a single subject, trial with higher blink rates were not associated with better performance. Therefore, possibly, people who are able to disengage easily, as indicated by an overall high blink rate, perform better in divergent thinking tasks. However, the link between blink rate and internal tasks is not clear at this point. Indeed, a more complex measurement of blink behavior might be necessary to understand the relationship.
In the final part of the project, I aimed to further understand the function of blinks through their neural correlates. I extracted the blink-related neural activity in the primary visual cortex (V1) of existing recordings of three rhesus monkeys during different sensory processing states. I analyzed spike related multi-unit responses, frequency dependent power changes, local field potentials and laminar distribution of activity while the animal watched a movie compared to when it was shown a blank screen. The results showed a difference in blink-related neural activity dependent on the processing state. This difference suggests a state dependent function of blinks.
Taken altogether, the work presented in this thesis suggests that eye blinks have an important function during cognitive and perceptual processes. Blinks seem to facilitate a disengagement from the external world and are therefore suppressed during intended processing of external stimuli.
One of the features that defines humans as extraordinarily social beings is their striking susceptibility to the gaze of others. The research reported in this dissertation was undertaken to advance our understanding of the role of gaze cues in low-level attentional and higher-order cognitive processes. In particular, effects of gaze were examined with regard to three aspects of human cognition: (1) social attention, (2) social interaction and (3) social understanding. Chapter 1 consists of three manuscripts that investigate the boundary conditions of attention capture by direct gaze and how gaze direction is integrated with facial context information. Manuscript 1 and 2 suggest two necessary requirements for attention capture by direct gaze: a meaningful holistic facial context and sharp foveal vision, respectively. Manuscript 3 shows approach/avoidance-congruency effects between gaze direction and emotion expression on attention. Chapter 2 of this dissertation explores the role of gaze in more naturalistic social scenarios. Manuscript 4 demonstrates that gaze behavior during a conversation shapes our perception of another person. Manuscript 5 builds on these findings by showing that these perceptions define our willingness to act in a prosocial way towards our interaction partner. Finally, chapter 3 adopts a broader perspective on social cognition research with a special focus on methodological aspects. Manuscript 6 is a review highlighting the significance of methodological aspects in social cognition research and stressing the importance of sophisticated decisions on task and stimulus materials. Manuscript 7 introduces a new instrument for the assessment of social understanding in adolescents. Initial application in a young sample group indicates that an understanding of another person’s mental states is a capacity that is still developing throughout adolescence. Both manuscripts of this final chapter include eye tracking data that suggest a relationship between gaze behavior and social understanding, a finding that further emphasizes the complex and multifaceted nature of social cognition. I conclude from the findings of this dissertation that research can benefit from adopting a broad view in terms of methodological as well as temporal aspects in order to capture human social cognition in its entirety.
During natural behavior, cognitive processes constantly coincide with body movements such as head or eye movements or blinks. However, during experimental investigations of cognitive processes, movements are often highly restricted which is rather unnatural. In order to improve our understanding of natural behavior, this thesis investigates the interaction between cognition and movements by focusing on spontaneous blinks, which naturally interact with other body movements.
Spontaneous blinks are inevitably connected to vision as they shut out incoming visual information. Both sensory-based and cognitive factors, for example, stimulus occurrence and evaluation, were reported to influence blink behavior. Our first study investigated if such influences are comparable for visual and non-visual input. The chosen experimental design allowed dissociating sensory-driven and cognitive influences, which then could be compared between the visual and auditory domain. Our results show that blinks are more strongly modulated during passive observation of visual input compared to auditory input. This modulation is however enhanced for both input modalities by an increased attentional demand. In addition, the cognitively defined meaning of a stimulus changes blink latency independent of the sensory domain. Overall, our findings show that spontaneous blinks and cognitive processes are linked beyond vision. Moreover, the underlying cognitive processes that influence blinks are largely the same across different sensory input indicating that blinks are profoundly integrated into our system.
When investigating natural behavior, it is important to consider that movements rarely occur in isolation, but are executed side by side. As these movements interact and have a link to cognitive processes, the complexity of our system increases. In order to take this complexity into account, the second part of the experimental research focused on movement interactions, more specifically on the interactions between blinks, pupil size and speaking. Our results reveal that speech-related motor activity increases blink rate and pupil size as well as modulates blink timing. This is in line with previous research that described a relation between different body and eye movements. Importantly, each bodily-induced change in eye movements affects visual information intake. Therefore, different movements can be tightly linked to perceptual processes through complex interactions.
Altogether, the work of this thesis provides rich evidence that movements and cognitive processes are deeply intertwined. Therefore, movements should be seen as an integral part of our system. Taking the relevance of movements and their interactions into account during experimental investigations is necessary in order to reveal a more realistic and complete picture of human natural behavior.
In der vorliegenden prospektiven Pilotstudie wurden die Hypothesen überprüft, dass es durch die nicht-invasive aurikuläre Vagusnervstimulation, jedoch nicht durch eine Kontrollstimulation am Ohrläppchen, zu einer Steigerung der Befindlichkeit, einer Verbesserung der Kognition und einem positiven Effekt auf die Herzratenvariabilität kommt.
Zusammenfassend konnten dabei in dieser Studie geringe Effekte der t-VNS auf einen kognitiven Parameter (F%-Wert des d2-Tests) sowie einen einzelnen HRV-Parameter (pNN50) gezeigt werden, wobei es Hinweise auf eine Intensitätsabhängigkeit der einzelnen Effekte gab. Auf die übrigen erfassten kognitiven Parameter und die weiteren gemessenen HRV-Parameter sowie die Befindlichkeit konnte kein Einfluss der t-VNS nachgewiesen werden. Bestätigt werden konnte das gute Sicherheitsprofil und die gute Tolerabilität der t-VNS.
Humans use their eyes not only as visual input devices to perceive the environment, but also as an action tool in order to generate intended effects in their environment. For instance, glances are used to direct someone else's attention to a place of interest, indicating that gaze control is an important part of social communication. Previous research on gaze control in a social context mainly focused on the gaze recipient by asking how humans respond to perceived gaze (gaze cueing). So far, this perspective has hardly considered the actor’s point of view by neglecting to investigate what mental processes are involved when actors decide to perform an eye movement to trigger a gaze response in another person. Furthermore, eye movements are also used to affect the non-social environment, for instance when unlocking the smartphone with the help of the eyes. This and other observations demonstrate the necessity to consider gaze control in contexts other than social communication whilst at the same time focusing on commonalities and differences inherent to the nature of a social (vs. non-social) action context. Thus, the present work explores the cognitive mechanisms that control such goal-oriented eye movements in both social and non-social contexts.
The experiments presented throughout this work are built on pre-established paradigms from both the oculomotor research domain and from basic cognitive psychology. These paradigms are based on the principle of ideomotor action control, which provides an explanatory framework for understanding how goal-oriented, intentional actions come into being. The ideomotor idea suggests that humans acquire associations between their actions and the resulting effects, which can be accessed in a bi-directional manner: Actions can trigger anticipations of their effects, but the anticipated resulting effects can also trigger the associated actions. According to ideomotor theory, action generation involves the mental anticipation of the intended effect (i.e., the action goal) to activate the associated motor pattern. The present experiments involve situations where participants control the gaze of a virtual face via their eye movements. The triggered gaze responses of the virtual face are consistent to the participant’s eye movements, representing visual action effects. Experimental situations are varied with respect to determinants of action-effect learning (e.g., contingency, contiguity, action mode during acquisition) in order to unravel the underlying dynamics of oculomotor control in these situations. In addition to faces, conditions involving changes in non-social objects were included to address the question of whether mechanisms underlying gaze control differ for social versus non-social context situations.
The results of the present work can be summarized into three major findings. 1. My data suggest that humans indeed acquire bi-directional associations between their eye movements and the subsequently perceived gaze response of another person, which in turn affect oculomotor action control via the anticipation of the intended effects. The observed results show for the first time that eye movements in a gaze-interaction scenario are represented in terms of their gaze response in others. This observation is in line with the ideomotor theory of action control. 2. The present series of experiments confirms and extends pioneering results of Huestegge and Kreutzfeldt (2012) with respect to the significant influence of action effects in gaze control. I have shown that the results of Huestegge and Kreutzfeldt (2012) can be replicated across different contexts with different stimulus material given that the perceived action effects were sufficiently salient. 3. Furthermore, I could show that mechanisms of gaze control in a social gaze-interaction context do not appear to be qualitatively different from those in a non-social context.
All in all, the results support recent theoretical claims emphasizing the role of anticipation-based action control in social interaction. Moreover, my results suggest that anticipation-based gaze control in a social context is based on the same general psychological mechanisms as ideomotor gaze control, and thus should be considered as an integral part rather than as a special form of ideomotor gaze control.