Perception of patterned vibratory stimulation: An evaluation of the tactile vision substitution system

Sensory substitution--The replacing of an impaired sensory channel by a properly functioning one--is possibly best manifested today in attempts to provide visual aids for the blind. The tactile vision substitution system (T.V.S.S.) is an example of one such visual aid. The system presents patterned tactile stimulation to the skin of the observer provided by the output of a closed-circuit television system. Research conducted with congenitally blind Ss in evaluation of the T.V.S.S. has provided useful information concerning the potentialities and limitations of the prototype systems, similarities and differences between tactile and visual perception, and the development of visual perception in the congenitally blind Investigation demonstrated that the congenitally blind Ss can learn to make valid judgements of three-dimensional displays with the T.V.S.S. Such judgements are made on the basis of properties contained in the proximal stimulation properties analogous to the monocular clues of depth presence in vision, such as linear-perspective, apparent elevation in the visual field, size change as a function of distance, occlusion, and texural gradients. Similarities have been noted between judgements made by sighted Ss using vision and by blind Ss using the T.V.S.S. on comparable tasks. A display consisting of two slightly displaced alternating lights is perceived in both situations as a single spot of light moving back-and-forth between two display boundaries. A rotating drum made up of alternate black and white stripes is, when stopped, perceived as briefly moving in the opposite direction. External localization of the source of stimulation also occurs with both sensory inputs. The major differences between the visual and tactile inputs that have been noted have occurred in form recognition tacks. Although blind Ss using the patterned tactile stimulation are able to identify both geometric forms and abstract patterns, accuracy is consistently lower than that of sighted Ss using vision, and the latencies for the blind Ss are significantly longer. It is hypothesized that the longer latencies for the blind Ss using the T.V.S.S. can be accounted for primarily by the need to hand-position the television camera during scanning. A major factor in the lower accuracy for the tactile group is the noted difficulty in detecting and identifying display features located within a mass of stimulation. This difficulty with internal display detail may be a function of sensory inhibition and/or masking. The research findings support a concept of sensory substitution as well as a theory of perception which stresses the modality of many qualities contained in visible displays. Further research is needed to determine the significance of sensor movement--either eye movements or camera manipulation--in the perceptual process

Attentional Narrowing: Triggering, Detecting and Overcoming a Threat to Safety.

In complex safety-critical domains, such as aviation or medicine, considerable multitasking requirements and attentional demands are imposed on operators who may, during off-nominal events, also experience high levels of anxiety. High task load and anxiety can trigger attentional narrowing – an involuntary reduction in the range of cues that can be utilized by an operator. As evidenced by numerous accidents, attentional narrowing is a highly undesirable and potentially dangerous state as it hampers information gathering, reasoning, and problem solving. However, because the problem is difficult to reproduce in controlled environments, little is known about its triggers, markers and possible countermeasures. Therefore, the goals of this dissertation were to (1) identify reliable triggers of attentional narrowing in controlled laboratory settings, (2) identify real-time markers of attentional narrowing that can also distinguish that phenomenon from focused attention – another state of reduced attentional field that, contrary to attentional narrowing, is deliberate and often desirable, (3) develop and test display designs that help overcome the narrowing of the attentional field. Based on a series of experiments in the context of a visual search task and a multi-tasking environment, novel unsolvable problems were identified as the most reliable trigger of attentional narrowing. Eye tracking was used successfully to detect and trace the phenomenon. Specifically, three eye tracking metrics emerged as promising markers of attentional narrowing: (1) the percentage of fixations, (2) dwell duration and (3) fixation duration in the display area where the novel problem was presented. These metrics were used to develop an algorithm capable of detecting attentional narrowing in real time and distinguishing it from focused attention. A command display (as opposed to status) was shown to support participants in broadening their attentional field and improving their time sharing performance. This dissertation contributes to the knowledge base in attentional narrowing and, more generally, attention management. A novel eye tracking based technique for detecting the attentional state and a promising countermeasure to the problem were developed. Overall, the findings from this research contribute to improved safety and performance in a range of complex high-risk domains.PHDIndustrial & Operations EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135773/1/jprinet_1.pd

An enactive approach to perceptual augmentation in mobility

Event predictions are an important constituent of situation awareness, which is a key objective for many applications in human-machine interaction, in particular in driver assistance. This work focuses on facilitating event predictions in dynamic environments. Its primary contributions are 1) the theoretical development of an approach for enabling people to expand their sampling and understanding of spatiotemporal information, 2) the introduction of exemplary systems that are guided by this approach, 3) the empirical investigation of effects functional prototypes of these systems have on human behavior and safety in a range of simulated road traffic scenarios, and 4) a connection of the investigated approach to work on cooperative human-machine systems. More specific contents of this work are summarized as follows: The first part introduces several challenges for the formation of situation awareness as a requirement for safe traffic participation. It reviews existing work on these challenges in the domain of driver assistance, resulting in an identification of the need to better inform drivers about dynamically changing aspects of a scene, including event probabilities, spatial and temporal distances, as well as a suggestion to expand the scope of assistance systems to start informing drivers about relevant scene elements at an early stage. Novel forms of assistance can be guided by different fundamental approaches that target either replacement, distribution, or augmentation of driver competencies. A subsequent differentiation of these approaches concludes that an augmentation-guided paradigm, characterized by an integration of machine capabilities into human feedback loops, can be advantageous for tasks that rely on active user engagement, the preservation of awareness and competence, and the minimization of complexity in human- machine interaction. Consequently, findings and theories about human sensorimotor processes are connected to develop an enactive approach that is consistent with an augmentation perspective on human-machine interaction. The approach is characterized by enabling drivers to exercise new sensorimotor processes through which safety-relevant spatiotemporal information may be sampled. In the second part of this work, a concept and functional prototype for augmenting the perception of traffic dynamics is introduced as a first example for applying principles of this enactive approach. As a loose expression of functional biomimicry, the prototype utilizes a tactile inter- face that communicates temporal distances to potential hazards continuously through stimulus intensity. In a driving simulator study, participants quickly gained an intuitive understanding of the assistance without instructions and demonstrated higher driving safety in safety-critical highway scenarios. But this study also raised new questions such as whether benefits are due to a continuous time-intensity encoding and whether utility generalizes to intersection scenarios or highway driving with low criticality events. Effects of an expanded assistance prototype with lane-independent risk assessment and an option for binary signaling were thus investigated in a separate driving simulator study. Subjective responses confirmed quick signal understanding and a perception of spatial and temporal stimulus characteristics. Surprisingly, even for a binary assistance variant with a constant intensity level, participants reported perceiving a danger-dependent variation in stimulus intensity. They further felt supported by the system in the driving task, especially in difficult situations. But in contrast to the first study, this support was not expressed by changes in driving safety, suggesting that perceptual demands of the low criticality scenarios could be satisfied by existing driver capabilities. But what happens if such basic capabilities are impaired, e.g., due to poor visibility conditions or other situations that introduce perceptual uncertainty? In a third driving simulator study, the driver assistance was employed specifically in such ambiguous situations and produced substantial safety advantages over unassisted driving. Additionally, an assistance variant that adds an encoding of spatial uncertainty was investigated in these scenarios. Participants had no difficulties to understand and utilize this added signal dimension to improve safety. Despite being inherently less informative than spatially precise signals, users rated uncertainty-encoding signals as equally useful and satisfying. This appreciation for transparency of variable assistance reliability is a promising indicator for the feasibility of an adaptive trust calibration in human-machine interaction and marks one step towards a closer integration of driver and vehicle capabilities. A complementary step on the driver side would be to increase transparency about the driver’s mental states and thus allow for mutual adaptation. The final part of this work discusses how such prerequisites of cooperation may be achieved by monitoring mental state correlates observable in human behavior, especially in eye movements. Furthermore, the outlook for an addition of cooperative features also raises new questions about the bounds of identity as well as practical consequences of human-machine systems in which co-adapting agents may exercise sensorimotor processes through one another.Die Vorhersage von Ereignissen ist ein Bestandteil des Situationsbewusstseins, dessen Unterstützung ein wesentliches Ziel diverser Anwendungen im Bereich Mensch-Maschine Interaktion ist, insbesondere in der Fahrerassistenz. Diese Arbeit zeigt Möglichkeiten auf, Menschen bei Vorhersagen in dynamischen Situationen im Straßenverkehr zu unterstützen. Zentrale Beiträge der Arbeit sind 1) eine theoretische Auseinandersetzung mit der Aufgabe, die menschliche Wahrnehmung und das Verständnis von raum-zeitlichen Informationen im Straßenverkehr zu erweitern, 2) die Einführung beispielhafter Systeme, die aus dieser Betrachtung hervorgehen, 3) die empirische Untersuchung der Auswirkungen dieser Systeme auf das Nutzerverhalten und die Fahrsicherheit in simulierten Verkehrssituationen und 4) die Verknüpfung der untersuchten Ansätze mit Arbeiten an kooperativen Mensch-Maschine Systemen. Die Arbeit ist in drei Teile gegliedert: Der erste Teil stellt einige Herausforderungen bei der Bildung von Situationsbewusstsein vor, welches für die sichere Teilnahme am Straßenverkehr notwendig ist. Aus einem Vergleich dieses Überblicks mit früheren Arbeiten zeigt sich, dass eine Notwendigkeit besteht, Fahrer besser über dynamische Aspekte von Fahrsituationen zu informieren. Dies umfasst unter anderem Ereigniswahrscheinlichkeiten, räumliche und zeitliche Distanzen, sowie eine frühere Signalisierung relevanter Elemente in der Umgebung. Neue Formen der Assistenz können sich an verschiedenen grundlegenden Ansätzen der Mensch-Maschine Interaktion orientieren, die entweder auf einen Ersatz, eine Verteilung oder eine Erweiterung von Fahrerkompetenzen abzielen. Die Differenzierung dieser Ansätze legt den Schluss nahe, dass ein von Kompetenzerweiterung geleiteter Ansatz für die Bewältigung jener Aufgaben von Vorteil ist, bei denen aktiver Nutzereinsatz, die Erhaltung bestehender Kompetenzen und Situationsbewusstsein gefordert sind. Im Anschluss werden Erkenntnisse und Theorien über menschliche sensomotorische Prozesse verknüpft, um einen enaktiven Ansatz der Mensch-Maschine Interaktion zu entwickeln, der einer erweiterungsgeleiteten Perspektive Rechnung trägt. Dieser Ansatz soll es Fahrern ermöglichen, sicherheitsrelevante raum-zeitliche Informationen über neue sensomotorische Prozesse zu erfassen. Im zweiten Teil der Arbeit wird ein Konzept und funktioneller Prototyp zur Erweiterung der Wahrnehmung von Verkehrsdynamik als ein erstes Beispiel zur Anwendung der Prinzipien dieses enaktiven Ansatzes vorgestellt. Dieser Prototyp nutzt vibrotaktile Aktuatoren zur Kommunikation von Richtungen und zeitlichen Distanzen zu möglichen Gefahrenquellen über die Aktuatorposition und -intensität. Teilnehmer einer Fahrsimulationsstudie waren in der Lage, in kurzer Zeit ein intuitives Verständnis dieser Assistenz zu entwickeln, ohne vorher über die Funktionalität unterrichtet worden zu sein. Sie zeigten zudem ein erhöhtes Maß an Fahrsicherheit in kritischen Verkehrssituationen. Doch diese Studie wirft auch neue Fragen auf, beispielsweise, ob der Sicherheitsgewinn auf kontinuierliche Distanzkodierung zurückzuführen ist und ob ein Nutzen auch in weiteren Szenarien vorliegen würde, etwa bei Kreuzungen und weniger kritischem longitudinalen Verkehr. Um diesen Fragen nachzugehen, wurden Effekte eines erweiterten Prototypen mit spurunabhängiger Kollisionsprädiktion, sowie einer Option zur binären Kommunikation möglicher Kollisionsrichtungen in einer weiteren Fahrsimulatorstudie untersucht. Auch in dieser Studie bestätigen die subjektiven Bewertungen ein schnelles Verständnis der Signale und eine Wahrnehmung räumlicher und zeitlicher Signalkomponenten. Überraschenderweise berichteten Teilnehmer größtenteils auch nach der Nutzung einer binären Assistenzvariante, dass sie eine gefahrabhängige Variation in der Intensität von taktilen Stimuli wahrgenommen hätten. Die Teilnehmer fühlten sich mit beiden Varianten in der Fahraufgabe unterstützt, besonders in Situationen, die von ihnen als kritisch eingeschätzt wurden. Im Gegensatz zur ersten Studie hat sich diese gefühlte Unterstützung nur geringfügig in einer messbaren Sicherheitsveränderung widergespiegelt. Dieses Ergebnis deutet darauf hin, dass die Wahrnehmungsanforderungen der Szenarien mit geringer Kritikalität mit den vorhandenen Fahrerkapazitäten erfüllt werden konnten. Doch was passiert, wenn diese Fähigkeiten eingeschränkt werden, beispielsweise durch schlechte Sichtbedingungen oder Situationen mit erhöhter Ambiguität? In einer dritten Fahrsimulatorstudie wurde das Assistenzsystem in speziell solchen Situationen eingesetzt, was zu substantiellen Sicherheitsvorteilen gegenüber unassistiertem Fahren geführt hat. Zusätzlich zu der vorher eingeführten Form wurde eine neue Variante des Prototyps untersucht, welche räumliche Unsicherheiten der Fahrzeugwahrnehmung in taktilen Signalen kodiert. Studienteilnehmer hatten keine Schwierigkeiten, diese zusätzliche Signaldimension zu verstehen und die Information zur Verbesserung der Fahrsicherheit zu nutzen. Obwohl sie inherent weniger informativ sind als räumlich präzise Signale, bewerteten die Teilnehmer die Signale, die die Unsicherheit übermitteln, als ebenso nützlich und zufriedenstellend. Solch eine Wertschätzung für die Transparenz variabler Informationsreliabilität ist ein vielversprechendes Indiz für die Möglichkeit einer adaptiven Vertrauenskalibrierung in der Mensch-Maschine Interaktion. Dies ist ein Schritt hin zur einer engeren Integration der Fähigkeiten von Fahrer und Fahrzeug. Ein komplementärer Schritt wäre eine Erweiterung der Transparenz mentaler Zustände des Fahrers, wodurch eine wechselseitige Anpassung von Mensch und Maschine möglich wäre. Der letzte Teil dieser Arbeit diskutiert, wie diese Transparenz und weitere Voraussetzungen von Mensch-Maschine Kooperation erfüllt werden könnten, indem etwa Korrelate mentaler Zustände, insbesondere über das Blickverhalten, überwacht werden. Des Weiteren ergeben sich mit Blick auf zusätzliche kooperative Fähigkeiten neue Fragen über die Definition von Identität, sowie über die praktischen Konsequenzen von Mensch-Maschine Systemen, in denen ko-adaptive Agenten sensomotorische Prozesse vermittels einander ausüben können

Psychomotor mechanisms underpinning performance changes in high-pressure situations

Pressurised situations have the potential to influence the performance of visual-motor tasks. The aim of this thesis was to investigate psychomotor mechanisms that may be responsible for such performance changes. A series of experimental studies were conducted in order to examine kinematic (Chapter 2) and attentional (Chapters 3 - 5) mechanisms. Performance pressure was successfully manipulated in all studies but performance was consistently maintained at a group-level. In the first experiment, individual differences in performance responses to pressure were found to correlate with kinematic changes, with decreases in movement amplitudes correlating with poorer performances. In the second experiment, pressure led to attentional narrowing as indicated by impaired performance of a useful field of view task. Pressure-induced changes in useful field of view correlated with performance changes. The third and fourth experiments demonstrated that pressure-induced changes in cognitive anxiety positively correlated with changes in the randomness of gaze behavior, which suggested that pressure has the potential to impact attentional control

Engineering Data Compendium. Human Perception and Performance, Volume 1

The concept underlying the Engineering Data Compendium was the product an R and D program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 1, which contains sections on Visual Acquisition of Information, Auditory Acquisition of Information, and Acquisition of Information by Other Senses

Effect of aging on measures of visual attention using dual tasks and visual search

In Canada, as baby boomers age, there will be an increase in the percentage of seniors within the general population (Statistics Canada, 2006). Seniors often have difficulty in performing certain everyday tasks and have greater risk of having health issues. As such, it becomes increasingly important to understand factors that pose difficulty for this group of people. As people get older, many visual functions such as visual acuity, contrast sensitivity, and glare are known to deteriorate (Haegerstrom-Portnoy, 2005). However, when considering activities that aid mobility such as driving and walking, vision related variables are not the only ones that create difficulty for older individuals. A sensory variable such as attention, in conjunction with vision, has been shown in previous studies to be a good predictor of difficulties encountered by the elderly (McGwin, Owsley, & Ball, 1998; Owsley, McGwin, Sloane, Stalvey, & Wells, 2001). Moreover, inattention and distraction seem to be common causes of automobile accidents as well as falls. The work load imposed on the working memory can impact distractibility and inattention. In mobility related activities such as driving and walking, individuals perceive objects that are increasing in size. Experiments were designed to investigate the factors that affect the perception of targets that are enlarging in size. Size matching of expanding targets to a previously presented static target, was investigated in a group of younger participants with normal vision using central or peripheral vision. The results show that size estimates differ depending on whether the target appears in the central visual field or in the periphery. The participants respond faster to targets that appear in the periphery compared to those in the centre/midline. In the subsequent set of experiments we compared the performance of younger and older participants using a dual task paradigm where individuals had to perform two tasks concurrently, one of which was to match the size of an enlarging target. Attention was modulated in the dual tasks by varying the difficulty of the secondary task. It has been found that older individuals have difficulty processing multiple visual tasks or performing multiple tasks in general (Pashler, 1994a, 1994b, 1998; Verhaeghen et al., 2003). Compared to younger individuals, older individuals were found to have greater performance difficulty in the highly demanding dual tasks. These results are compared to those observed in studies of psychological refractory period effects. The differences between the young and older individuals are discussed with respect to limited capacity and bottle neck models of attention. Furthermore, eye movement measures in the dual tasks seem to provide evidence of difficulty in task switching for the older observers. The thesis also investigated the functional field of view of younger and older individuals. By assessing the functional field of view (FFOV) using a method employed earlier by Coeckelbergh et al., (2004a), significant overall age related differences were found. Multiple characteristics of what might affect the FFOV as measured by the attended field of view (AFOV) were also investigated (e.g., impact of a pop out distracter and divided attention). It was found that differences between the two age groups occurred in all conditions. The presence of irrelevant distracters had a greater impact on the older individuals compared to the younger group, whereas divided attention or the presence of the pop out distracter did not affect either age group. Attention processing seemed to be similar for both the younger and older individuals and, therefore, the differences between the age groups appear to be at a quantitative level rather than a qualitative level

Dynamics of sensorimotor behavior in electrolocation and electrocommunication

Pedraja F. Dynamics of sensorimotor behavior in electrolocation and electrocommunication. Bielefeld: Universität Bielefeld; 2019.How are external sensory stimuli perceived, integrated and represented within the central nervous system? How does the nervous system generate appropriate behavioral responses based on this input and how does this behavior affect perception? The above questions have in common that they view sensory input and motor control as two sides of the sensorimotor loop. In this closed-loop system, actions inevitably generate sensory flow that can serve to organize behavior. To look, to smell, to touch, etc. are perceptual acts that depend on the interaction, coordination and interpretation of motor and sensory information through neural mechanisms. Active sensory systems are particularly amenable to the study of the reciprocal relations of motor and sensory components, as parts of closed loop control structures. A notable advantage of these sensory systems is the experimental accessibility of their sensory input, both in terms of its measurement and in terms of detailed modeling reconstructions of the input. In the case of weakly electric fish studied in this thesis, the animals sense and process environmental perturbations of a self-generated electric field. The fact that this field serves as the carrier of sensory information and at the same time is controlled by the animal, enables to precisely determine aspects of sensing that are often hard to obtain or quantify in sensory systems that do not actively generate the carrier: where, when and what an animal samples. Drawing on these benefits, my thesis focuses on the role of motor and electromotor behavior in sensorimotor integration. For this, a biophysical model for the active and passive electroreception was combined with physiological recordings and behavioral approaches. The central topics addressed are: (i) Object detection and sensorimotor learning. The sensory information obtained by the African species Gnathonemus petersii while learning a detection task was computationally reconstructed using boundary element methods (BEM). This revealed that the improved task performance was paralleled by an enhancement of the quality of the sensory information, which was mediated by changes of the electromotor patterns. The versatile manner in which the fish changed the spatial and temporal allocation of otherwise stable motor components not only improved the quality of the sensory input, but also resulted in shifts of the animals' attention towards the object. (ii) Dynamic choice of optimal behavior. Extending on the above results, I next explored how changing the distance of an object to be detected by the fish influenced the electromotor behavior. With increasing complexity (distance), the fish resorted to a new motor strategy. This consisted in first approaching a salient element in the arena, from where the fish then made a perceptually-guided decision. This interpretation is backed up by analyzing the trajectories in the context of attractors, revealing that the focus of attention was altered in a task-dependent manner. (iii) Distance estimation using a non-visual form of motion parallax. In the above experiments it is implicitly assumed that electric fish acquire spatial information like the position and distance of a target. How this is achieved dynamically has been addressed recently. Based on the properties of the electric field geometry, theoretical considerations indicated that relative movements might provide depth information. In a behavioral assay, I show that this novel form of electric parallax exists and is used across phylogenetically distant taxa of weakly electric fish (Apteronotus albifrons, Eigenmania virescens and Gnathonemus petersii). Notably, these species electrically sample the environment in temporally distinct ways (using discrete pulses or quasi-sinusoidal waves), suggesting an ubiquitous role for parallax in electric sensing. (iv) The role of multi-modal integration in socially relevant agonistic behaviour. Extending on the above results, I next addressed if passive as well as active electric sensory information can be used to evaluate more complex features of the environment. For this I turned to social interactions of the South American species Gymnotus omarorum to study if an electrical assessment of a competitor is possible. Based on modeling the sensory consequences of dyadic encounters, I showed that passive as well as active sensory information can drive agonistic interactions. This suggests that aggressive interactions may be triggered by information about contenders obtained through the active and passive electrosensory system. (v) Hierarchy as a social consequence of electric interactions. The above analysis indicated that active as well as passive electrolocation may contribute in a non-reciprocal manner to social interactions. Gymnotus omarorum then was tested in intra- and intersexual dyads in small plain arenas. A sex-independent dominant-subordinate status emerged after highly aggressive contests. Subordinates signaled their submission by retreating and emitting specific (submissive) electric signals. The emergence of a dominant-subordinate status was also observed in a larger arena after longer but milder contests with rare electric signaling of submission with a unique consequence: the persistence of dominance over time with no outcome reversion

Large as being on top of the world and small as hitting the roof: A shared magnitude representation for the comparison of emotions and numbers

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Previous work on the direct Speed–Intensity Association (SIA) on comparative judgment tasks involved spatially distributed responses over spatially distributed stimuli with high motivational significance like facial expressions of emotions. This raises the possibility that the inferred stimulus-driven regulation of lateralized motor reactivity described by SIA, which was against the one expected on the basis of a valence-specific lateral bias, was entirely due to attentional capture from motivational significance (beyond numerical cognition). In order to establish the relevance of numerical cognition on the regulation of attentional capture we ran two complementary experiments. These involved the same direct comparison task on stimulus pairs that were fully comparable in terms of their analog representation of intensity but with different representational domain and motivational significance: symbolic magnitudes with low motivational significance in experiment 1 vs. emotions with rather high motivational significance in experiment 2. The results reveal a general SIA and point to a general mechanism regulating comparative judgments. This is based on the way spatial attention is captured toward locations that contain the stimulus which is closest in term of relative intensity to the extremal values of the series, regardless from its representational domain being it symbolic or emotiona

Irrelevant information processing: inquiry into the validity of a neural-based model

This dissertation contributed to the field of irrelevant information processing as a subfield of cognitive psychology. More specifically, the scope of this dissertation was to investigate how relevant information processing affects the quality of irrelevant information processing. To be able to account for the results obtained in the initial part of the thesis, we introduced the hypothesis that the translation from stimulus to response is not only influenced by the similarity of the mental codes associated with relevant and irrelevant information and responses (e.g. the dimensional overlap model; Kornblum et al., 1990), but also by the similarity of the neural regions that are involved in processing of the stimuli and responses. This similarity at the neural level was named “neural overlap” (in analogy of dimensional overlap), and was defined as the cortical and functional proximity of the processing regions of relevant and irrelevant information. In a subsequent part of the thesis, attempts were made to scrutinize the generality of the neural overlap hypothesis in a series of studies. Together, the ambiguous data gathered by these experiments question the feasibility of the neural overlap hypothesis