The present study was designed to look at inhibition of return within a schizophrenic population for the first time. Inhibition of return is an attentional phenomenon that has been studied with a number of populations, and has been shown to be present in normal individuals. Based on the disattention hypothesis put forth by Cromwell and colleagues (e.g., Cromwell & Dokecki, 1968), it was hypothesized that patients with schizophrenia would show an impaired inhibition of return. Twenty-eight inpatients with schizophrenia, and 19 normal comparisons were evaluated on a visual inhibition of return task. Consistent with hypotheses, schizophrenia patients have significant impairments in inhibition of return compared to normal comparison participants. Further, the relative lack of inhibition of return in the schizophrenic group was found to be strongest to stimuli in the left visual field. These results provide initial support for a reconceptualization of the disattention hypothesis.

The most common evidence for inhibition of return (IOR) is the robust finding of increased response times to targets that appear at previously cued locations following a cue-target interval exceeding ~ 300 ms. In a variation on this paradigm, Abrams and Dobkin (1994a) observed that IOR was greater when a saccadic response was made to a peripheral than to a central arrow, leading to the conclusion that saccadic responses to peripheral targets comprise motoric and perceptual components (the two components theory for IOR) whereas saccadic responses to a central target comprise a single motoric component. In contrast to the foregoing findings, Taylor and Klein (2000) discovered that IOR for saccadic responses was equivalent for randomly intermixed central and peripheral targets, suggesting a single motoric flavor under these conditions. To resolve the apparent discrepancy, a strict replication of Abrams and Dobkin was conducted in which central and peripheral targets were either blocked or mixed. In the blocked design, peripheral targets resulted in more IOR than central targets, while in the mixed design, replicating Taylor and Klein (2000), target type had no bearing on the magnitude of IOR (i.e., equivalent IOR was obtained for both target types). This pattern of results suggests that the confound inherent in Abrams and Dobkin's blocked design generated a pattern of results that "masqueraded" as two components of IOR.

Prompted by oculomotor theories of attention, the present experiments explore the role of saccade activation in the generation of two cueing effects: exogenous capture (Experiment 1) and inhibition of return (IOR; Experiment 2). Exogenous capture is shortlived and marked by faster responding toward recently stimulated locations, whereas the longer-lasting IOR manifests as slower responding toward those locations. Within each experiment, Group A performed in a dual-task in which on most trials a peripheral target had to be identified but infrequently a central arrow probe called for an eye movement instead, while for Group B the tasks were the same except saccade trials were frequent and target identification trials were infrequent. In Experiment 1, for group A uninformative cues captured attention as measured by faster digit identification at the cued location, an effect not accompanied by saccade activation. For group B, cues generated saccade activation without capturing attention. Thus saccade activation need not accompany exogenous covert capture, and covert capture need not accompany saccade activation. In Experiment 2, group A exhibited IOR which slowed digit identification, but did not affect saccadic responding, while Group B exhibited no IOR in either digit identification or eye movement trials. This finding provides converging evidence that IOR can be dichotomized into two forms; one which delays motor production itself (Evidenced amply elsewhere, e.g., Taylor & Klein, 2000) and another which delays responding by applying inhibition at a perceptual-motor interface which can operate in independence from its motoric cousin.

This thesis encompasses five chapters. Chapter 1 details the background literature for how the inhibition of return effect manifests in 3D environments. Additional summary is provided about how positioning cues and targets within the boundary of the same objects affects the spread of IOR when compared to when attention is cued in empty space. Finally, the literature review also provides a background for whether the IOR effect is affected by a viewer-centered or world-centered frame of reference. Chapters 2-4 are empirical chapters. Chapter 2 observes a depth-specific IOR effect in a 3D composed of pictorial depth cues. Chapter 3 suggests that this depth-specificity can only occur when cues and targets are positioned in different objects rather than when positioned within a single object. Chapter 4 investigates how the distances between viewer and cue, viewer and target, and cue and target affect the magnitude of IOR, suggesting that the world-centered reference frame influences IOR. Chapter 5 serves as a general discussion and conclusion chapter, discussing the findings and implications of each empirical chapter. / The distribution of human attention in space can be modulated by spatial and temporal factors. This dissertation studied inhibition of return (IOR), a robust behavioural effect obtained through a spatial cueing paradigm where observers exhibit slower detection times to a target appearing over 300 ms after a cue in a previously cued location. Most research has studied the IOR effect in two-dimensional space; thus, it remains unclear whether, in three-dimensional space (3D) space, slower reaction times occur due to a target appearing in the same world location (defined in 3D coordinates) or in the same retinal location as the cue (i.e., anywhere along an observer’s line of sight to the cue). My thesis examines IOR in a computer-simulated 3D environment, with the location of the cue and target residing in the same versus different depth/distance position either within the same or different object and either relative to the observer or to the world environment. Following a general literature review (Chapter 1), the first empirical chapter (Chapter 2) demonstrates that IOR is depth-specific when the direction of depth switch between cue to target occurs from far-to-near space, suggesting a behavioural advantage for near space in the human attention system. Chapter 3 shows that this depth-specificity and depth-asymmetry of IOR is maintained only when cues and targets are not part of the same object; object membership can therefore override the depth-specific property of IOR in 3D scenes. Chapter 4 introduces motion of the viewpoint, showing that IOR is depth-specific when the cue and target appear in different depth locations in the world environment even when located at the same relative distance from the observer’s viewpoint. Thus, IOR could be the result of an inhibitory tag placed at a location relative to the environment rather than at a location relative to the viewpoint. / Dissertation / Doctor of Science (PhD) / Human attention can be distributed over space and affected by external events. Prior research using 2D environments has shown that some time after the first stimulus (a cue), the reaction time to a subsequent stimulus (a target) appearing in the same location is typically slower compared to when this target appears elsewhere. Thus, attention likely moves away from a previously observed to more novel location of interest. I examined, in a 3D environment, whether this “location” of reduced attention resides in the same 3D location or retinal location as that of the cue. I also assessed the impact on reaction time for when the cue and target belong to the same or different object and when their locations differ in reference to the observer or world environment. My research suggests that humans maintain a higher level of attention for nearer space when the cue previously appears at a farther location.

Our attentional system has the remarkable ability to allow familiar contexts to guide attentional orienting, while still retaining the ability to orient rapidly to novelty in our environment. Many cognitive paradigms have been used to investigate the particular process that is responsible for orienting attention to novel events, but each paradigm has produced a unique set of boundary conditions. One such paradigm has studied an effect labelled Inhibition of Return (IOR), which has been argued to tap into an attentional mechanism that rapidly orients attention to novelty, but only in the spatial domain. The IOR effect was initially taken as evidence of a fundamental difference between spatial attentional orienting and non-spatial attentional orienting. However, there were a small number of early studies that questioned the view that the IOR effect can only be observed in the spatial domain. In this dissertation, I built upon the evidence for non-spatial IOR by uncovering the effect using a Target-Target (TT) procedure. Although a number of prior studies had failed to observe non-spatial IOR using a TT procedure, I was able to uncover non-spatial IOR effects using a TT procedure by introducing an intervening event. The IOR-like effect that was uncovered using this procedure was labelled the intervening event effect. I introduced a dual process framework to explain the intervening event effect. According to the dual process framework, intervening events between consecutive targets can disrupt an episodic integration process, allowing the influence of a separate opposing process to be measured more directly. Using the dual process framework, I studied the level of processing of the intervening event that was necessary to disrupt episodic integration, as well as the context-sensitivity of the episodic integration process. Lastly, I investigated the role of subjective expectancy in the studies used to measure non-spatial IOR in this thesis. / Thesis / Doctor of Philosophy (PhD)

Em tarefas de tempo de reação, uma pista visual pode engatilhar diversos processos, que facitam ou inibem diferentes estágios do processamento do estímulo-alvo. As características da tarefa podem modular os efeitos da pista. Neste estudo, investigamos as possíveis causas dos efeitos inibitórios da pista. Em experimentos em que foi usada uma tarefa de discriminação vai/não-vai, um efeito inibitório foi encontrado quando um valor fixo assincronia entre o início pista e o início do estímulo-alvo (SOA) foi usado, mas não quando o valor de SOA foi variado no decorrer da tarefa. Na tarefa de discriminação de escolha, nenhum efeito initório da pista foi observado, enquanto na tarefa de detecção houve facilitação. Nós propomos que o efeito inibitório na tarefa do tipo vai-não/vai se origina da inibição da tendência de responder automaticamente ao aparecimento da pista. Essa inibição tornaria mais lenta a resposta ao estímulo-alvo subsequente. / In reaction time tasks, a visual cue can trigger several processes and each of these processes can have either a facilitatory or inhibitory influence on different stages of target processing. It has been suggested that task set might modulate cuing effects. In the present study, we investigated the possible causes of inhibitory cueing effects. In experiments involving a go/no-go discrimination task, an inhibitory cueing effect on reaction time was found when a fixed asynchrony between cue onset and target onset (SOA) was used, but not when varied SOAs was used. In a choice discrimination task no inhibitory cueing effect was observed, while in a detection task there was a facilitatory cueing effect. We propose that the inhibitory cueing effect in the go/no-go task arises from the inhibition of an automatic tendency to respond to the cue. This would slow responding to the subsequent target stimulus. Our results suggest that a response inhibition to the cue may contribute to the inhibition of return effect.

Inhibition of return (IOR) is a cognitive phenomenon whereby reaction times (RTs) are slower to cued relative to uncued targets at cue-target onset asynchronies (CTOAs) greater than approximately 300 ms. One important theory of IOR proposes that there are two mutually exclusive forms of IOR, with an attentional/perceptual form arising when the oculomotor system is actively suppressed, and a motoric form arising when it is engaged (Taylor & Klein, 2000). Other theories propose that IOR is the result of multiple, additive neural mechanisms (Abrams & Dobkin, 1994). Here, we have performed computational simulations and empirical investigations in an attempt to reconcile these two competing theories. Using a dynamic neural field (DNF) model of the intermediate layers of the superior colliculus (iSC), we have modeled both a sensory adaptation mechanism of IOR, and a motoric mechanism resulting from the aftereffects of saccadic eye movements. Simulating these mechanisms, we replicated behavior and neurophysiology in a number of variations on the traditional cue-target paradigm (Posner, 1980). Predictions driven by these simulations have led to the proposal of many behavioral and neuroimaging experiments which further examine the plausibility of a 2-mechanisms theory of IOR. Contrary to our original predictions, we demonstrated that saccades are biased away from cued targets in a paired target saccade averaging paradigm, even at short CTOAs. In paradigms thought to recruit both sensory and motoric mechanisms, we robustly demonstrated that there are at least two independent, additive mechanisms of IOR when tasks require saccadic responses to targets. When similar paradigms were tested with manual responses to targets, additivity effects did not hold, implying that the motoric mechanism of IOR does not transfer from the oculomotor to skeletomotor systems. Furthermore, across numerous experiments using event-related potential (ERP) techniques, we have demonstrated that P1 component reductions are neither necessary, nor sufficient, for the behavioral exhibition of IOR. We propose that a comprehensive framework for behavioral IOR must include (at least) four independent neural mechanisms, differentially active depending on circumstances, including sensory adaptation, saccadic aftereffects, local inhibition, and cortical habituation.

Em tarefas de tempo de reação, uma pista visual pode engatilhar diversos processos, que facitam ou inibem diferentes estágios do processamento do estímulo-alvo. As características da tarefa podem modular os efeitos da pista. Neste estudo, investigamos as possíveis causas dos efeitos inibitórios da pista. Em experimentos em que foi usada uma tarefa de discriminação vai/não-vai, um efeito inibitório foi encontrado quando um valor fixo assincronia entre o início pista e o início do estímulo-alvo (SOA) foi usado, mas não quando o valor de SOA foi variado no decorrer da tarefa. Na tarefa de discriminação de escolha, nenhum efeito initório da pista foi observado, enquanto na tarefa de detecção houve facilitação. Nós propomos que o efeito inibitório na tarefa do tipo vai-não/vai se origina da inibição da tendência de responder automaticamente ao aparecimento da pista. Essa inibição tornaria mais lenta a resposta ao estímulo-alvo subsequente. / In reaction time tasks, a visual cue can trigger several processes and each of these processes can have either a facilitatory or inhibitory influence on different stages of target processing. It has been suggested that task set might modulate cuing effects. In the present study, we investigated the possible causes of inhibitory cueing effects. In experiments involving a go/no-go discrimination task, an inhibitory cueing effect on reaction time was found when a fixed asynchrony between cue onset and target onset (SOA) was used, but not when varied SOAs was used. In a choice discrimination task no inhibitory cueing effect was observed, while in a detection task there was a facilitatory cueing effect. We propose that the inhibitory cueing effect in the go/no-go task arises from the inhibition of an automatic tendency to respond to the cue. This would slow responding to the subsequent target stimulus. Our results suggest that a response inhibition to the cue may contribute to the inhibition of return effect.

Visual selective attention operates in space- and object-based frames of reference. Stimulus salience and task demands influence whether a space- or object-based frame of reference guides attention. I conducted two experiments for the present dissertation to evaluate age patterns in the role of inhibition in object-based attention. The biased competition account (Desimone & Duncan, 1995) proposes that one mechanism through which targets are selected is through suppression of irrelevant stimuli. The inhibitory deficit hypothesis (Hasher & Zacks, 1988) predicts that older adults do not appropriately suppress or ignore irrelevant information. The purpose of the first study was to evaluate whether inhibition of return (IOR) patterns, originally found in a laboratory setting, could be replicated with online data collection (prompted by the COVID-19 pandemic). Inhibition of return is a cognitive mechanism to bias attention from returning to previously engaged items. In a lab setting, young and older adults produced location- and object-based IOR. In the current study, both types of IOR were also observed within object boundaries, although location-based IOR from data collected online was smaller than that from the laboratory. In addition, there was no evidence of an age-related reduction in IOR effects. There was some indication that sampling differences or testing circumstances led to increased variability in online data.The purpose of the second study was to evaluate age differences in top-down inhibitory processes during an attention-demanding object tracking task. Data were collected online. I used a dot-probe multiple object tracking (MOT) task to evaluate distractor suppression during target tracking. Both young and older adults showed poorer dot-probe detection accuracies when the probes appeared on distractors compared to when they appeared at empty locations, reflecting inhibition. The findings suggest that top-down inhibition works to suppress distractors during target tracking and that older adults show a relatively preserved ability to inhibit distractor objects. The findings across both experiments support models of selective attention that posit that goal-related biases suppress distractor information and that inhibition can be directed selectively by both young and older adults on locations and objects in the visual field.

Estudos sobre a orientação da atenção que utilizam o procedimento de Posner têm demonstrado dois efeitos: uma facilitação inicial no processamento do estímulo que aparece no lugar para onde dirigiu-se a atenção e subsequentemente um prejuízo no processamento deste estímulo, neste local. Em um trabalho anterior não evidenciamos o efeito facilitador da orientação da atenção em uma tarefa de tempo de reação simples. Levantamos algumas hipóteses para explicar este efeito oposto. Para testarmos tais hipóteses realizamos 6 experimentos. Nos dois primeiros, examinamos em que medida a presença de tentativas de pegada influenciava a expressão do efeito negativo do estímulo precedente. No terceiro examinamos a possibilidade do estímulo precedente ser capaz de reduzir a responsividade. No quarto equalizamos a intensidade efetiva do estímulo alvo nas duas posições em que ele podia ser apresentado (mesma e oposta). No quinto e no sexto avaliamos a evolução temporal do efeito negativo do estímulo precedente, na tentativa de determinar até que ponto ela teria alguma relação com a evolução temporal esperada para um mascaramento anterógrado. O sexto experimento poderia adicionalmente fornecer alguma pista de uma contribuição de uma inibição de retorno, neste caso precoce, para o efeito negativo encontrado. Em todos esses casos a influência atencional do estímulo precedente presumivelmente continuaria a ocorrer, mas seria suplantada pela influência contrária coexistente. Em conjunto, nossos resultados sugerem que o efeito negativo do estímulo precedente em uma tarefa de tempo de reação simples, se deve a uma interferência com o processamento do estímulo alvo, caracterizando uma inibição de natureza sensorial. / Studies about attention orienting that use Posner?s procedure have demonstrated two effects: an initial facilitation of responsivit when the target stimulus appears in the same location as the prime stimulus and a subsequent inhibition of this responsvity. In a previous work we could not find the early facilitatory effect of attention orienting in a simple reaction time task. The hypotheses that we raised to explain this unexpected finding were tested in six experiments. In the first two ones, we examined whether the presence of catch trials influenced the expression of the negative effect of the prime stimulus. In the third experiment we examined the possibility that the prime stimulus reduced responsivity. In the fourth experiment we equalized the intensity of the target stimulus in the two locations where it could be presented (same and opposite). In the fifth and in sixth experiments we evaluated the time course of the negative effect of the prime stimulus, as an attempt to verify whether it would be compatible with a forward masking process. The sixth experiment could additionally give some clue about a contribution of inhibition of return, in this case precocious, to the found negative effect. In all these cases the attentional influence of the prime stimulus would presumably continue to occur, but would be supplanted by the contrary negative of this stimulus influence. Overall, our results suggest that the negative effect of the prime stimulus in a simple reaction time task is due to an interference with the processing of the target stimulus, characterizing a kind of sensory inhibition.