It’s About Time: Studying the Encoding of Duration

Processing temporal information is crucial when interacting with the external world. Analyzing the temporal properties of an event, such as its duration and the rate at which things change, allows us to learn about temporal regularities in the world around us. We use this knowledge to predict future events, guide our decisions, and plan the timing of our actions. In addition, it also allows us to track our behavior and synchronize our interactions with our environment so that we can perform complicated behavioral tasks that require precise timing. Despite the importance of using temporal information to guide behavior, the process by which we extract and code temporal information is poorly understood. In this thesis, we investigate both duration and temporal frequency processing. Chapters 2-4 focus on duration processing by investigating the way in which duration information is encoded from visual information. We used duration adaptation paradigms to probe the encoding of duration and aimed to better understand duration-tuned mechanisms proposed to underlie duration processing. We aimed to answer questions about the relative position of duration-tuned mechanisms in the (visual) processing hierarchy, the nature of the sensory signals that duration-tuned mechanisms respond to, and how the responses of duration-tuned mechanisms are modulated by attentional demands. In chapter 5 we present a study on temporal frequency processing in which we investigate the way in which temporal frequency information is maintained during periods when the source of information is absent. Together, these studies expand our knowledge on duration encoding and temporal frequency processing, while also providing more insight into novel paradigms that can be used to study these forms of temporal processing

An Investigation of the Spatial Selectivity of the Duration After-Effect

Adaptation to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered evidence for the involvement of duration-selective mechanisms in duration encoding. Here, we investigated whether the encoding of duration - by duration-selective mechanisms - occurs early on in the visual processing hierarchy. To this end, we investigated the spatial specificity of the duration after-effect in two experiments. We measured the duration after-effect at adapter-test distances ranging between 0 and 15° of visual angle and for within- and between- hemifield presentations. We replicated the duration after-effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this duration after-effect occurred at all measured distances, with no evidence for a decrease in the magnitude of the after-effect at larger distances or across hemifields. This shows that adaptation to duration does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy

An Investigation of the Spatial Selectivity of the Duration After-Effect

Adaptation to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered evidence for the involvement of duration-selective mechanisms in duration encoding. Here, we investigated whether the encoding of duration - by duration-selective mechanisms - occurs early on in the visual processing hierarchy. To this end, we investigated the spatial specificity of the duration after-effect in two experiments. We measured the duration after-effect at adapter-test distances ranging between 0 and 15° of visual angle and for within- and between- hemifield presentations. We replicated the duration after-effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this duration after-effect occurred at all measured distances, with no evidence for a decrease in the magnitude of the after-effect at larger distances or across hemifields. This shows that adaptation to duration does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy

Eye Tracking the Use of a Collapsible Facets Panel in a Search Interface (Poster)

<p>Facets can provide an interesting functionality in digital libraries. However, while some research shows facets are important, other research found<br>facets are only moderately used. Therefore, in this exploratory study we compare two search interfaces; one where the facets panel is always visible and one where the facets panel is hidden by default. Our main research question is “<em>Is folding the facets panel in a digital library search interface beneficial to academic users?</em>” By performing an eye tracking study with N=24, we measured search efficiency, distribution of attention and user satisfaction. We found no significant differences in the eye tracking data nor in usability feedback and<br>conclude that collapsing facets is neither beneficial nor detrimental.</p> <p> </p

The duration aftereffect does not reflect adaptation to perceived duration

Recent studies have provided evidence for a role of duration-tuned channels in the encoding of duration. Duration encoding in these channels is thought to reflect the time between responses to the onset and offset of an event. This notion is in apparent conflict with studies that demonstrate that the perceived duration of an event can vary independently from the time separating its perceived onset and offset. Instead, these studies suggest that duration encoding is sensitive to other temporal aspects of a sensory event. In the current study, we investigated whether duration-tuned channels encode duration based on the time between the on- and offset of an event (onset-offset duration), or if they encode a duration corresponding to the perceived duration of that event. We used a duration illusion to dissociate onset-offset duration and perceived duration and measured whether repeated exposure to illusion-inducing stimuli caused adaptation to the onset-offset duration or the perceived duration of these illusion-inducing stimuli. We report clear evidence for adaptation to the onset-offset duration of illusion-inducing stimuli. This finding supports the notion that duration-tuned mechanisms respond to the time between the onset and offset of an event, without necessarily reflecting the duration perceived, and eventually reported by the participant. Implications for the duration channel model and the mechanisms underlying duration illusions are discussed

Representing dynamic stimulus information during occlusion

Human observers maintain a representation of the visual features of objects when they become occluded. This representation facilitates the interpretation of occluded events and allows us to quickly identify objects upon reappearing. Here we investigated whether visual features that change over time are also represented during occlusion. To answer this question we used an illusion from the time perception domain in which the perceived duration of an event increases as its temporal frequency content increases. In the first experiment we demonstrate temporal frequency based modulation of duration both when the object remains visible as well as when it becomes temporarily occluded. Additionally, we demonstrate that this effect cannot be explained by modulations of duration as a result of pre- and post-occlusion presentation of the object. In a second experiment we corroborate this finding by demonstrating that modulations of the perceived duration of occluded events depend on the expected temporal frequency content of the object during occlusion. Together these results demonstrate that the dynamic properties of an object are represented during occlusion. We conclude that the representations of occluded objects contain a wide range of features derived from the period when the object was still visible, including information about both the static and dynamic properties of the object

The duration aftereffect does not reflect adaptation to perceived duration

Recent studies have provided evidence for a role of duration-tuned channels in the encoding of duration. Duration encoding in these channels is thought to reflect the time between responses to the onset and offset of an event. This notion is in apparent conflict with studies that demonstrate that the perceived duration of an event can vary independently from the time separating its perceived onset and offset. Instead, these studies suggest that duration encoding is sensitive to other temporal aspects of a sensory event. In the current study, we investigated whether duration-tuned channels encode duration based on the time between the on- and offset of an event (onset-offset duration), or if they encode a duration corresponding to the perceived duration of that event. We used a duration illusion to dissociate onset-offset duration and perceived duration and measured whether repeated exposure to illusion-inducing stimuli caused adaptation to the onset-offset duration or the perceived duration of these illusion-inducing stimuli. We report clear evidence for adaptation to the onset-offset duration of illusion-inducing stimuli. This finding supports the notion that duration-tuned mechanisms respond to the time between the onset and offset of an event, without necessarily reflecting the duration perceived, and eventually reported by the participant. Implications for the duration channel model and the mechanisms underlying duration illusions are discussed