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Age-related changes in emotional processing are complex, with a bias toward positive information. However, the impact of aging on emotional responses in positive everyday situations remains unclear. Virtual Reality (VR) has emerged as a promising tool for investigating emotional processing, offering a unique balance between ecological validity and experimental control. Yet, limited evidence exists regarding its efficacy to elicit positive emotions in older adults. Our study aimed to explore age-related differences in positive emotional responses to immersion in both social and nonsocial virtual emotional environments. We exposed 34 younger adults and 24 older adults to natural and social 360-degree video content through a low immersive computer screen and a highly immersive Head-Mounted Display, while recording participants' physiological reactions. Participants also provided self-report of their emotions and sense of presence. The findings support VR's efficacy in eliciting positive emotions in both younger and older adults, with age-related differences in emotional responses influenced by the specific video content rather than immersion level. These findings underscore the potential of VR as a valuable tool for examining age-related differences in emotional responses and developing VR applications to enhance emotional wellbeing across diverse user populations., (© 2024. The Author(s).)

Understanding the influence of emotions on social interactions is important for a global understanding of the dynamics of human behavior. In this study, we investigated the interplay between emotions, spontaneous approach or avoidance tendencies, and the regulation of interpersonal distance. Fifty-seven healthy adults participated in a three-part experiment involving exposure to approaching or withdrawing emotional faces (neutral, happy, sad, fearful, disgusted, angry). The sequence began with an initial computerized stop-distance task, followed by a postural task in which participants' approach or avoidance tendencies were quantified via center of pressure (CoP-Y) displacements on a force platform, and concluded with a final computerized stop-distance task. Our findings revealed a gradient in postural responses, with the most forward CoP-Y displacements for neutral and happy faces, indicative of approach tendencies. These were followed by lesser forward displacements for sad and fearful faces, and most pronounced backward displacements for disgusted and angry faces, indicating avoidance. Furthermore, we observed modulations in participants' preferred interpersonal distance based on emotional cues, with neutral and happy faces associated with shorter distances, and disgusted and angry faces linked to larger distances. Despite these similar results, no direct correlation was found between CoP-Y and preferred interpersonal distance, underscoring a dissociation between spontaneous and voluntary social behaviors. These results contribute to a better understanding of how emotional expressions shape social interactions and underscore the importance of considering emotional cues, postural action tendencies, and interpersonal distance in facilitating successful social interactions., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Lebert et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

While the recognition of ambiguous emotions is crucial for successful social interactions, previous work has shown that they are perceived differently depending on whether they are viewed on male or female faces. The present paper aims to shed light on this phenomenon by exploring two hypotheses: the confounded signal hypothesis, which posits the existence of perceptual overlaps between emotions and gendered morphotypes, and the social role hypothesis, according to which the observer's responses are biased by stereotypes. Participants were asked to categorise blended faces (i.e. artificial faces made ambiguous by mixing two emotions) in a forced-choice task. Six emotions were used to create each blend (neutral, surprise, sadness, fear, happiness, anger), for a total of 15 expressions. We then applied signal detection theory - considering both the morphotype of the stimuli and the participants' gender - to distinguish participants' perceptual processes from their response biases. The results showed a perceptual advantage for anger on male faces and for sadness on female faces. However, different strategies were deployed when labelling emotions on gendered morphotypes. In particular, a response bias towards angry male faces establishes their special status, as they resulted in both excellent detection and a tendency to be over-reported, especially by women.

Immersive technologies, such as Virtual Reality (VR), have great potential for enhancing users' emotions and wellbeing. However, how immersion, Virtual Environment contents, and sense of presence (SoP) influence emotional responses remains to be clarified to efficiently foster positive emotions. Consequently, a total of 26 participants (16 women, 10 men, 22.73 ± 2.69 years old) were exposed to 360-degree videos of natural and social contents on both a highly immersive Head-Mounted Display and a low immersive computer screen. Subjective emotional responses and SoP were assessed after each video using self-reports, while a wearable wristband collected continuously electrodermal activity and heart rate to record physiological emotional responses. Findings supported the added value of immersion, as more positive emotions and greater subjective arousal were reported after viewing the videos in the highly immersive setting, regardless of the video contents. In addition to usually employed natural contents, the findings also provide initial evidence for the effectiveness of social contents in eliciting positive emotions. Finally, structural equation models shed light on the indirect effect of immersion, through spatial and spatial SoP on subjective arousal. Overall, these are encouraging results about the effectiveness of VR for fostering positive emotions. Future studies should further investigate the influence of user characteristics on VR experiences to foster efficiently positive emotions among a broad range of potential users.

The functional consequences of the visual system lateralization referred to as "eye dominance" remain poorly understood. We previously reported shorter hand reaction times for targets appearing in the contralateral visual hemifield with respect to the dominant eye (DE). Here, we further explore this contralateral bias by studying the influence of laterally placed visual distractors on vertical saccade trajectories, a sensitive method to assess visual processing. In binocular conditions, saccade trajectory curvature was larger toward a distractor placed in the contralateral hemifield with respect to the DE (e.g., in the left visual hemifield for a participant with a right dominant eye) than toward one presented in the ipsilateral hemifield (in the right visual hemifield in our example). When two distractors were present at the same time, the vertical saccade showed curvature toward the contralateral side. In monocular conditions, when one distractor was presented, a similar larger influence of the contralateral distractor was observed only when the viewing eye was the DE. When the non dominant eye (NDE) was viewing, curvature was symmetric for both distractor sides. Interestingly, this curvature was as large as the one obtained for the contralateral distractor when the DE was viewing, suggesting that eye dominance consequences rely on inhibition mechanisms present when the DE is viewing. Overall, these results demonstrate that DE influences visual integration occurring around saccade production and support a DE-based contralateral visual bias., (© 2022. The Author(s).)

In everyday life, interactions between humans are generally modulated by the value attributed to the situation, which partly relies on the partner's behavior. A pleasant or cooperating partner may trigger an approach behavior in the observer, while an unpleasant or threatening partner may trigger an avoidance behavior. In this context, the correct interpretation of other's intentions is crucial to achieve satisfying social interactions. Social cues such as gaze direction and facial expression are both fundamental and interrelated. Typically, whenever gaze direction and facial expression of others communicate the same intention, it enhances both the interlocutor's gaze direction and the perception of facial expressions (i.e., shared signal hypothesis). For instance, an angry face with a direct gaze is perceived as more intense since it represents a threat to the observer. In this study, we propose to examine how the combination of others' gaze direction (direct or deviated) and emotional facial expressions (i.e., happiness, fear, anger, sadness, disgust, and neutrality) influence the observer's gaze perception and postural control. Gaze perception was indexed by the cone of direct gaze (CoDG) referring to the width over which an observer feels someone's gaze is directed at them. A wider CoDG indicates that the observer perceived the face as looking at them over a wider range of gaze directions. Conversely, a narrower CoDG indicates a decrease in the range of gaze directions perceived as direct. Postural control was examined through the center of pressure displacements reflecting postural stability and approach-avoidance tendencies. We also investigated how both gaze perception and postural control may vary according to participants' personality traits and emotional states (e.g., openness, anxiety, etc.). Our results confirmed that gaze perception is influenced by emotional faces: a wider CoDGs was observed with angry and disgusted faces while a narrower CoDG was observed for fearful faces. Furthermore, facial expressions combined with gaze direction influence participants' postural stability but not approach-avoidance behaviors. Results are discussed in the light of the approach-avoidance model, by considering how some personality traits modulate the relation between emotion and posture., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lebert, Chaby, Guillin, Chekroun and Vergilino-Perez.)

During social interactions, perception of emotions affects motor behaviour by triggering responses like freezing or approach and avoidance reactions. It is however difficult to get a clear picture of the relationship between emotion and posture as previous studies showed inconsistent results, due to methodological differences on stimuli and/or the postural measures used. In this study, we thoroughly investigate how the perception of emotions affects postural control and action tendencies, by contrasting two types of stimuli (emotional static faces or emotional videos) expressing different types of basic emotions (happy, fear, angry, sad, disgust and neutral). We also take into account some other contributing factors relying on stable individual traits (e.g., extraversion, neuroticism, conscientiousness, empathy, etc) and emotional state (e.g., anxiety). Our results show that dynamic stimuli have a greater impact than static stimuli on postural control. Moreover, a crucial aspect of our work lay in the modulation of the relationship between emotions and posture, by stable individual traits.

Hemispheric specialization refers to the fact that cerebral hemispheres are not equivalent and that cognitive processes are lateralized in the brain. Although the potential links between handedness and the left hemisphere specialization for language have been widely studied, little attention has been paid to other motor preferences, such as eye dominance, that also are lateralized in the brain. For example, saccadic accuracy is higher in the hemifield contralateral to the dominant eye compared to the ipsilateral hemifield. Saccade accuracy is, however, also known to be sensitive to other functional asymmetries, such as the lateralization of visuo-spatial attention in the right hemisphere of the brain. Using a global effect paradigm in three different saccade latency ranges, we here propose to use saccade accuracy as an indicator of visual functional asymmetries. We show that for the shortest latencies, saccade accuracy is higher in the left than in the right visual hemifield, which could be due to the lateralization of visuo-spatial attention in the right hemisphere. For the longest latencies, however, saccade accuracy is higher toward the right than the left hemifield, probably due to the lateralization of local and global processing in the left and right hemispheres, respectively. These results could have a major impact on studies designed to measure the degree of lateralization of individuals. We here discuss both the theoretical and clinical contributions of these results.

The saccadic system presents asymmetries. Notably, saccadic peak velocity is higher in temporal than in nasal saccades, and in centripetal than in centrifugal saccades. It has already been shown that eye dominance strength relates to naso-temporal asymmetry, but its links with centripetal-centrifugal asymmetry has never been tested. The current study tested both naso-temporal and centripetal-centrifugal asymmetries simultaneously to provide a finer and continuous measure of eye dominance strength. We asked 63 participants to make centripetal and centrifugal saccades from five different locations. Analysis of saccadic peak velocity shows that eye dominance strength modulates every saccadic asymmetry tested. For the first time, we propose a graduated measure of eye dominance strength on a continuum model. The model ranges from weak to very strong eye dominance. Weak eye dominance corresponds to increased saccadic asymmetries whereas strong eye dominance corresponds to no asymmetries. Furthermore, our results provide new insights into the neurophysiological origins of saccadic asymmetries. Modulation of both naso-temporal and centripetal-centrifugal asymmetries by eye dominance strength supports the involvement of V1 in these saccadic asymmetries., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

It is well known that the saccadic system presents multiple asymmetries. Notably, temporal (as opposed to nasal) saccades, centripetal (as opposed to centrifugal) saccades (i.e., the recentering bias) and saccades from the abducting eye (as opposed to the concomitant saccades from the adducting eye) exhibit higher peak velocities. However, these naso-temporal and centripetal-centrifugal asymmetries have always been studied separately. It is thus unknown which asymmetry prevails when there is a conflict between both asymmetries, i.e., in case of centripetal nasal saccades or centrifugal temporal saccades. This study involved binocular recordings of eye movements to examine both the naso-temporal and centripetal-centrifugal asymmetries so as to determine how they work together. Twenty-eight participants had to make saccades toward stimuli presented either centrally or in the periphery in binocular conditions. We found that temporal and abducting saccades always exhibit higher peak velocities than nasal and adducting saccades, irrespective of their centripetal or centrifugal nature. However, we showed that the velocity advantage for centripetal saccades is only found for temporal and not for nasal saccades. Such a result is of importance as it could provide new insights about the physiological origins of the asymmetries found in the saccadic system.

Unlike handedness, sighting eye dominance, defined as the eye unconsciously chosen when performing monocular tasks, is very rarely considered in studies investigating cerebral asymmetries. We previously showed that sighting eye dominance has an influence on visually triggered manual action with shorter reaction time (RT) when the stimulus appears in the contralateral visual hemifield with respect to the dominant eye (Chaumillon et al. 2014). We also suggested that eye dominance may be more or less pronounced depending on individuals and that this eye dominance strength could be evaluated through saccadic peak velocity analysis in binocular recordings (Vergilino-Perez et al. 2012). Based on these two previous studies, we further examine here whether the strength of the eye dominance can modulate the influence of this lateralization on manual reaction time. Results revealed that participants categorized as having a strong eye dominance, but not those categorized as having a weak eye dominance, exhibited the difference in RT between the two visual hemifields. This present study reinforces that the analysis of saccade peak velocity in binocular recordings provides an effective tool to better categorize the eye dominance. It also shows that the influence of eye dominance in visuo-motor tasks depends on its strength. Our study also highlights the importance of considering the strength of eye dominance in future studies dealing with brain lateralization., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Purpose: Neuroimaging studies have shown that the dominant eye is linked preferentially to the ipsilateral primary visual cortex. However, its role in perception still is misunderstood. We examined the influence of eye dominance and eye dominance strength on saccadic parameters, contrasting stimulations presented in the two hemifields., Methods: Participants with contrasted eye dominance (left or right) and eye dominance strength (strong or weak) were asked to make a saccade toward a target displayed at 5° or 7° left or right of a fixation cross. In some trials, a distractor at 3° of eccentricity also was displayed either in the same hemifield as the target (to induce a global effect on saccade amplitude) or in the opposite hemifield (to induce a remote distractor effect on saccade latency)., Results: Eye dominance did influence saccade amplitude as participants with strong eye dominance showed more accurate saccades toward the target (weaker global effect) in the hemifield contralateral to the dominant eye than in the ipsilateral one. Such asymmetry was not found in participants with weak eye dominance or when a remote distractor was used., Conclusions: We show that eye dominance strength influences saccade target selection. We discuss several arguments supporting the view that such advantage may be linked to the relationship between the dominant eye and ipsilateral hemisphere. French Abstract.

Introduction: The dominant eye is defined as the one we unconsciously choose when we have to perform monocular tasks. In the field of clinical neuro-ophthalmology, it is well-established that ocular dominance plays a key role in several eye diseases. Furthermore, the accurate quantification of ocular dominance is crucial with regard to certain surgical techniques. However, classical preoperative tests cannot determine the amount of ocular dominance., Materials and Methods: In order to obtain further insight into the phenomenon of ocular dominance, we study its influence at behavioral and neurophysiological levels (experiments 1 and 2). Based on these new data, we suggest a method to improve quantification of ocular dominance (experiment 3)., Results: We demonstrate that ocular dominance has an influence on hand movements and on interhemispheric transfer time. Moreover, we show that an analysis of the dynamics of saccades allows us to sort out participants with strong or weak ocular dominance., Conclusion: In conclusion, this better understanding of the phenomenon of ocular dominance, coupled with the analysis of saccadic dynamics, might, in the short or medium term, lead to the establishment of a quick and straightforward battery of tests allowing determination of the amount of ocular dominance for each patient., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

In order to further our understanding of action-blindsight, four hemianopic patients suffering from visual field loss contralateral to a unilateral occipital lesion were compared to six healthy controls during a double task of verbally reported target detection and saccadic responses toward the target. Three oculomotor tasks were used: a fixation task (i.e., without saccade) and two saccade tasks (eliciting reflexive and voluntary saccades, using step and overlap 600 ms paradigms, respectively), in separate sessions. The visual target was briefly presented at two different eccentricities (5° and 8°), in the right or left visual hemifield. Blank trials were interleaved with target trials, and signal detection theory was applied. Despite their hemifield defect, hemianopic patients retained the ability to direct a saccade toward their contralesional hemifield, whereas verbal detection reports were at chance level. However, saccade parameters (latency and amplitude) were altered by the defect. Saccades to the contralesional hemifield exhibited longer latencies and shorter amplitudes compared to those of the healthy group, whereas only the latencies of reflexive saccades to the ipsilesional hemifield were altered. Furthermore, healthy participants showed the expected latency difference between reflexive and voluntary saccades, with the latter longer than the former. This difference was not found in three out of four patients in either hemifield. Our results show action-blindsight for saccades, but also show that unilateral occipital lesions have effects on saccade generation in both visual hemifields.

Previous studies have demonstrated a left perceptual bias while looking at faces, due to the fact that observers mainly use information from the left side of a face (from the observer's point of view) to perform a judgment task. Such a bias is consistent with the right hemisphere dominance for face processing and has sometimes been linked to a left gaze bias, i.e. more and/or longer fixations on the left side of the face. Here, we recorded eye-movements, in two different experiments during a gender judgment task, using normal and chimeric faces which were presented above, below, right or left to the central fixation point or on it (central position). Participants performed the judgment task by remaining fixated on the fixation point or after executing several saccades (up to three). A left perceptual bias was not systematically found as it depended on the number of allowed saccades and face position. Moreover, the gaze bias clearly depended on the face position as the initial fixation was guided by face position and landed on the closest half-face, toward the center of gravity of the face. The analysis of the subsequent fixations revealed that observers move their eyes from one side to the other. More importantly, no apparent link between gaze and perceptual biases was found here. This implies that we do not look necessarily toward the side of the face that we use to make a gender judgment task. Despite the fact that these results may be limited by the absence of perceptual and gaze biases in some conditions, we emphasized the inter-individual differences observed in terms of perceptual bias, hinting at the importance of performing individual analysis and drawing attention to the influence of the method used to study this bias.

Words presented to the right visual field (RVF) are recognized more readily than those presented to the left visual field (LVF). Whereas the attentional bias theory proposes an explanation in terms of attentional imbalance between visual fields, the attentional advantage theory assumes that words presented to the RVF are processed automatically while LVF words need attention. In this study, we exploited coupling between attention and saccadic eye movements to orient spatial attention to one or the other visual field. The first experiment compared conditions wherein participants had to remain fixated centrally or had to make a saccade to the visual field in which subsequent verbal stimuli were displayed. The orienting of attention by saccade preparation improved performance in a lexical decision task in both the LVF and the RVF. In the second experiment, participants had to make a saccade either to the visual field where verbal stimuli were presented subsequently or to the opposite side. For RVF as well as for LVF presentation, saccade preparation toward the opposite side decreased performance compared to the same side condition. These results are better explained by the attentional bias theory, and are discussed in the light of a new attentional theory dissociating two major components of attention, namely preparation and selection., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Purpose: Hemispheric specialization in saccadic control is still under debate. Here we examine the latency, gain, and peak velocity of reactive and voluntary leftward and rightward saccades to assess the respective roles of eye and hand dominance., Methods: Participants with contrasting hand and eye dominance were asked to make saccades toward a target displayed at 5°, 10°, or 15° left or right of the central fixation point. In separate sessions, reactive and voluntary saccades were elicited by Gap-200, Gap-0, Overlap-600, and Antisaccade procedures., Results: Left-right asymmetries were not found in saccade latencies but appeared in saccade gain and peak velocity. Regardless of the dominant hand, saccades directed to the ipsilateral side relative to the dominant eye had larger amplitudes and faster peak velocities., Conclusions: Left-right asymmetries can be explained by naso-temporal differences for some subjects and by eye dominance for others. Further investigations are needed to examine saccadic parameters more systematically in relation to eye dominance. Indeed, any method that allows one to determine ocular dominance from objective measures based on saccade parameters should greatly benefit clinical applications, such as monovision surgery.

Saccadic adaptation maintains saccade accuracy and has been studied with targeting saccades, i.e. saccades that bring the gaze to a target, with the classical intra-saccadic step procedure in which the target systematically jumps to a new position during saccade execution. Post-saccadic visual feedback about the error between target position and the saccade landing position is crucial to establish and maintain adaptation. However, recent research focusing on two-saccade sequences has shown that exploring saccades, i.e. saccades that explore an object, resists this classical intra-saccadic step procedure but can be adapted by systematically changing the main parameter used for their coding: stimulus size. Here, we adapted an exploring saccade and a targeting saccade in two separate experiments, using the appropriate adaptation procedure, and we tested whether the adaptation induced on one saccade type transferred to the other. We showed that whereas classical targeting saccade adaptation does not transfer to exploring saccades, the reciprocal transfer (i.e., from exploring to targeting saccades) occurred when targeting saccades aimed for a spatially extended stimulus, but not when they aimed for an isolated target. These results show that, in addition to position errors, size errors can drive adaptation, and confirm that exploring vs. targeting a stimulus leads to two different motor planning modes., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Purpose: To compare the amount, the retention, and the extinction of saccadic adaptation in two groups: 9 adults (23-36 years old) and 9 children (11-14 years old)., Methods: The paradigm used was a classical double-step target to elicit the shortening of saccade gains in response to a 2° backward step (20% of target eccentricity). Two conditions were run in the pre- and postadaptation phases without and with postsaccadic visual feedback, to allow examination of the retention and the extinction of saccadic adaptation., Results: Adaptation of reactive saccades occurred in children as well as adults. Both groups showed a progressive shortening of saccade amplitude and good retention. The main difference concerned the speed of extinction, i.e., return to baseline, which was slower for children., Conclusions: Cerebral structures involved in human short-term adaptation of reactive saccades are functional in regard to adaptive shortening of saccade amplitude. Divergent patterns in the extinction of adaptation between children and adults suggested that lengthening of saccade gain is not yet well established in children. Further investigation is needed to clarify whether processes responsible for backward adaptation are mature before those for forward adaptation.

Saccadic adaptation maintains saccade accuracy and has been studied with the intrasaccadic target displacement procedure: displacing a target backwards (or forwards) during saccade execution gradually decreases (or increases) subsequent saccade amplitude. Adaptation has traditionally been studied with targeting saccades which bring the eyes onto a new object. Within-object saccades take the eye from one position in an object to another position in the same object and have been shown to resist the intrasaccadic target displacement procedure. The amplitude of within-object saccades depends on object size rather than position, and we therefore hypothesized that within-object saccades might adapt in response to an intrasaccadic change in object size. In separate sessions, we increased or decreased object size during within-object saccade execution. Results showed amplitude lengthening or shortening, respectively. Furthermore, within-object saccade adaptation seems to share several characteristics with targeting-saccade adaptation.

Previous studies have shown that a saccade is coded in a specific reference frame according to its goal: to aim for a new object or to explore an object which has already been fixated. In a two saccade sequence, the second saccade aiming for a new object is programmed in a retinocentric reference frame in which the spatial location of the second object is stored in spatial memory before the first saccade and updated after its execution. The second saccade exploring the same object is coded in an oculocentric reference frame in which object size is directly transformed into a fixed motor vector, encoded in motor memory before the first saccade and simply applied after its execution. The integration of parafoveal visual information appears to be crucial in the selection of the appropriate reference frame. The two experiments presented here investigate how and when the saccadic system integrates visual information to plan a sequence of saccades. In separate blocks, subjects were asked to execute a sequence of prosaccades directed toward a single object or two short objects, or to execute a sequence of antisaccades in the opposite direction of the stimuli. The latency of the initial saccade was modulated by using the Gap-200, Gap-0 and Overlap-600 ms paradigms. The results show that the time available for segmenting the visual stimulation into discrete objects and application of a specific reference frame according to this segmentation is critical for saccadic planning.

In the antisaccade task, subjects must execute an eye movement away from a visual target. Correctly executing an antisaccade requires inhibiting a prosaccade toward the visual target and programming a movement to the opposite side. This movement could be based on the inversion of the visual vector, corresponding to the distance between the fixation point and the visual target, or the motor vector of the unwanted prosaccade. We dissociated the two vectors by means of saccadic adaptation. Adaptation can be observed when systematic targeting errors are caused by the displacement of the visual target during the saccade. Adaptation progressively modifies saccade amplitude (defined by the motor vector) such that it becomes appropriate to the postsaccadic stimulus position and thus different from the visual vector of the target. If antisaccade preparation depended on visual vector inversion, rightward prosaccade adaptation should not transfer to leftward antisaccades (which are based on the same visual vector) but should transfer to rightward antisaccades (which are based on a visual vector inside the adaptation field). If antisaccade preparation depended on motor vector inversion, rightward prosaccade adaptation should transfer to leftward antisaccades (which are based on the same, adapted motor vector) but should not transfer to rightward antisaccades (which are based on a nonadapted motor vector). The results are in line with the first hypothesis, showing that vector inversion precedes saccadic adaptation and suggesting that antisaccade preparation depends on the inversion of the visual target vector.

The accuracy of saccadic eye movements is maintained by saccadic adaptation. Post-saccadic visual feedback about the error between the target position and the saccade endpoint is crucial to the adaptive process. The present experiments examine the adaptation of saccades that select a new target object (between-object saccades) and that of saccades that would not aim for a selected target but execute a fixed motor vector (within-object saccades). We show that the post-saccadic visual error, induced by the intra-saccadic back step, leads to the adaptation of between-object saccades but not of within-object saccades. Furthermore, between-object saccade adaptation does not transfer to within-object saccades. These results suggest that saccadic adaptation depends on the selection of a precise target object.

Executing sequences of accurate saccadic eye movements supposes the use of signals carrying information about the first saccade for updating the predetermined motor plan of the subsequent saccades. The present study examines the signals used in planning a second saccade when subjects made two successive saccades towards one long or two short peripheral objects displayed before the first saccade execution. Different first eye movement signals could be used: desired eye movement signals, representing the movement necessary for attaining the intended target, or actual eye movement signals, representing the movement actually executed. Experimental dissociation of desired and actual eye movement signals is made possible by adaptive modifications of the first saccade, obtained by transfer of single saccade adaptation, during which the motor vector was progressively modified in response to the systematic intra-saccadic step of a single target. Whether the second saccade used the actual eye movement signal to compensate or not for the adaptive changes in the first saccade depended on which object properties were relevant for saccade planning. Compensation was observed for saccades that aimed for a new object (between-object saccades) because adaptation modifies relative object location. No compensation was observed for saccades that explored an extended object (within-object saccades). Implications for the on-line control of subsequent eye movements are discussed.

The role of the perceptual organization of the visual display on eye movement control was examined in two experiments using a task where a two-saccade sequence was directed toward either a single elongated object or three separate shorter objects. In the first experiment, we examined the consequences for the second saccade of a small displacement of the whole display during the first saccade. We found that between-object saccades compensated for the displacement to aim for a target position on the new object whereas within-object saccades did not show compensation but were coded as a fixed motor vector applied irrespective of wherever the preceding saccade landed. In the second experiment, we extended the paradigm to examine saccades performed in different directions. The results suggest that the within-object and between-object saccade distinction is an essential feature of saccadic planning.

The eye movements we make to look at objects require that the spatial information contained in the object's image on the retina be used to generate a motor command. This process is known as sensorimotor transformation and has been generally addressed using simple point targets. Here, we investigate the sensorimotor transformation involved in planning double saccade sequences directed at one or two objects. Using both visually guided saccades toward stationary objects and objects subjected to intrasaccadic displacements, and memory-guided saccades, we found that the coordinate transformations required to program the second saccade were different for saccades aimed at a new target object and saccades that scanned the same object. While saccades aimed at a new object were updated on the basis of the actual eye position, those that scanned the same object were performed with a fixed amplitude, irrespective of the actual eye position. Our findings demonstrate that different abstract representations of space are used in sensory-to-motor transformations, depending on what action is planned on the objects.

When orienting to a newly appearing display, evidence shows that two saccadic eye movements are often prepared together. By looking the relation between the landing positions of the first and the second saccade, we examine the frame of reference used for the preparation of the second saccade aiming for a new object or exploring within the same object. We demonstrate that the action to be performed on the object affects the coding of the second saccade. A second saccade directed to a new object is coded to aim for a target position on it and is adjusted to the landing position of the first saccade, whereas a second saccade within the same object is coded as a fixed motor vector applied irrespective of the initial landing position on the object.

Readers' eye movements were monitored when they read either normal sentences or sentences with masked or disappearing text (in which the fixated word disappeared or was masked after 60 ms). The goals of the research were to investigate (1) whether a gap effect occurred in reading and (2) the influence of linguistic and visual factors on oculomotor control. The results of a number of global analyses of eye movements under disappearing text conditions clearly demonstrated that there is no gap effect in reading. However, comparative analyses across a number of local measures in the experiments indicated that cognitive/lexical processes, as well as the continual uptake of visual information, influence eye movement control during reading. A persistent visual object throughout fixation caused refixations and even when a fixated word had disappeared (or been masked), there were significant effects of word frequency and word length.

Evidence from recent studies bolsters the idea of preestablished motor plans in scanning isolated items. Thus, refixation saccades are preplanned at the same time as the primary saccade directed to a peripheral item and are completed with fixed amplitudes irrespective of the first fixation position in the item. In order to examine the saccadic system's ability to correct the motor plan during its execution on the basis of new visual information, an experiment was conducted in which 11-letter strings were changed to two 5-letter strings at different times after the primary saccade was directed to the stimulus. The results demonstrate that the saccadic system is able to cancel the preplanned refixation saccade and plan a saccade directed to the next item only when the new visual information is available at least 220 msec before the execution of the saccade.

Eye movements were recorded during the reading of long words presented in isolation. Overall, the decision to refixate was found to depend on both length and frequency of the word, while refixation amplitude depended only on word length. This finding corroborates the assumption that most refixation saccades are preplanned on the basis of the parafoveal word length. However, cancellation of such a plan is possible and could be linked to the lexical processing during the first fixation into the word. Finally, a small proportion of refixations are corrective saccades, related to an oculomotor error. Theoretical implications for models of eye movement control during reading are discussed.

Participants read sentences containing high- or low-frequency target words under normal reading conditions or disappearing-text conditions (in which the word that was fixated disappeared after 60 ms). Even though the fixated word had disappeared after 60 ms, there was still a robust frequency effect wherein readers fixated longer on low-frequency words than on high-frequency words. Thus, the results are consistent with cognitive-control models of eye movement control and inconsistent with visual/oculomotor-control models. Although the uptake of visual information is clearly important for reading, it is the cognitive processes associated with understanding the fixated words that drive the eyes through the text.

We investigated how a postsaccadic visual error affects the latency of the subsequent saccade. Observers made sequences of saccades directed to a single object or three separate objects, which could be displaced backward or onward during the primary saccade. The results showed an increase of second saccade latency after a backward displacement and a decrease of second saccade latency after an onward displacement. Moreover, second saccade latencies were particularly short after an onward displacement which resulted in a primary saccade landing position outside the boundary of the objects. We interpret the latency differences in terms of known effects within the saccadic system, specifically the sensitivity to the pattern of visual stimulation, particularly at and near the fovea, and the inverse correlation between secondary saccade amplitudes and secondary saccade latencies.