Enumeration in Alzheimer's disease and other late life psychiatric syndromes

Previous studies suggest that visual enumeration is spared in normal aging but impaired in abnormal aging (late stage Alzheimer's disease, AD), raising the task's potential as a marker of dementia. Experiment 1 compared speeded enumeration of 1–9 random dots in early stage AD, vascular dementia (VAD), depression, and age-matched controls. Previous deficits were replicated but they were not specific to AD, with the rate of counting larger numerosities similarly slowed relative to controls by both AD and VAD. Determination of subitizing span was complicated by the surprisingly slower enumeration of one than of two items, especially in AD patients. Experiment 2 showed that AD patients’ relative difficulty with one item persisted with further practice and extended to the enumeration of targets among distractors. However, it was abolished when pattern recognition was possible (enumerating dots on a die). Although an enumeration test is unlikely to help differentiate early AD from other common dementias, the unexpected pattern of patients’ performance challenges current models of enumeration and requires further investigation

List-level transfer effects in temporal learning: further complications for the list-level proportion congruent effect

Congruency effects are larger when most trials are congruent relative to incongruent. According to the conflict adaptation account, this proportion congruent effect is due to the decreased attention to words when most of the trials are conflicting. This paper extends on previous work arguing that list-level (contingency-unbiased) proportion congruent effects might be explainable by temporal learning biases. That is, congruency effects are larger in an easier task (i.e., mostly congruent) due to the faster pace of the task. Two non-conflict analogues of the proportion congruent effect are presented, one with a contrast manipulation and another with a contingency manipulation. Critically, both experiments control for potential item-specific temporal learning biases by intermixing biased context and unbiased transfer items. Results show a proportion congruent-like interaction for both item types, supporting the notion of task-wide temporal learning as an explanation for list-level proportion congruency effects. Distributional analyses lend further credence to the temporal learning account by showing that proportion congruent and proportion congruent-like effects are localised in the fastest and intermediate responses

Temporal Expectation Indexed by Pupillary Response

Forming temporal expectations plays an instrumental role for the optimization of behavior and allocation of attentional resources. Although the effects of temporal expectations on visual attention are well-established, the question of whether temporal predictions modulate the behavioral outputs of the autonomic nervous system such as the pupillary response remains unanswered. Therefore, this study aimed to obtain an online measure of pupil size while human participants were asked to differentiate between visual targets presented after varying time intervals since trial onset. Specifically, we manipulated temporal predictability in the presentation of target stimuli consisting of letters which appeared after either a short or long delay duration (1.5 vs. 3 s) in the majority of trials (75%) within different test blocks. In the remaining trials (25%), no target stimulus was present to investigate the trajectory of preparatory pupillary response under a low level of temporal uncertainty. The results revealed that the rate of preparatory pupillary response was contingent upon the time of target appearance such that pupils dilated at a higher rate when the targets were expected to appear after a shorter as compared to a longer delay period irrespective of target presence. The finding that pupil size can track temporal regularities and exhibit differential preparatory response between different delay conditions points to the existence of a distributed neural network subserving temporal information processing which is crucial for cognitive functioning and goal-directed behavior.</p

Temporal Expectation Indexed by Pupillary Response

Forming temporal expectations plays an instrumental role for the optimization of behavior and allocation of attentional resources. Although the effects of temporal expectations on visual attention are well-established, the question of whether temporal predictions modulate the behavioral outputs of the autonomic nervous system such as the pupillary response remains unanswered. Therefore, this study aimed to obtain an online measure of pupil size while human participants were asked to differentiate between visual targets presented after varying time intervals since trial onset. Specifically, we manipulated temporal predictability in the presentation of target stimuli consisting of letters which appeared after either a short or long delay duration (1.5 vs. 3 s) in the majority of trials (75%) within different test blocks. In the remaining trials (25%), no target stimulus was present to investigate the trajectory of preparatory pupillary response under a low level of temporal uncertainty. The results revealed that the rate of preparatory pupillary response was contingent upon the time of target appearance such that pupils dilated at a higher rate when the targets were expected to appear after a shorter as compared to a longer delay period irrespective of target presence. The finding that pupil size can track temporal regularities and exhibit differential preparatory response between different delay conditions points to the existence of a distributed neural network subserving temporal information processing which is crucial for cognitive functioning and goal-directed behavior.</p

Demonstrating perception without visual awareness: Double dissociations between priming and masking

A double dissociation impressively demonstrates that visual perception and visual awareness can be independent of each other and do not have to rely on the same source of information (T. Schmidt & Vorberg, 2006). Traditionally, an indirect measure of stimulus processing and a direct measure of visual awareness are compared (dissociation paradigm or classic dissociation paradigm, Erdelyi, 1986; formally described by Reingold & Merikle, 1988; Merikle & Reingold, 1990; Reingold, 2004). If both measures exhibit opposite time courses, a double dissociation is demonstrated. One tool that is well suited to measure stimulus processing as fast visuomotor response activation is the response priming method (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). Typically, observers perform speeded responses to a target stimulus preceded by a prime stimulus, which can trigger the same motor response by sharing consistent features (e.g., shape) or different responses due to inconsistent features. While consistent features cause speeded motor responses, inconsistent trials can induce response conflicts and result in slowed responses. These response time differences describe the response priming effect (Klotz & Neumann, 1999; Klotz & Wolff, 1995; see also F. Schmidt et al., 2011; Vorberg et al., 2003). The theoretical background of this method forms the Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), which assumes that priming is based on neuronal feedforward processing within the visuomotor system. Lamme and Roelfsema (2000; see also Lamme, 2010) claim that this feedforward processing does not generate visual awareness because neuronal feedback and recurrent processes are needed. Fascinatingly, while prime visibility can be manipulated by visual masking techniques (Breitmeyer & Öğmen, 2006), priming effects can still increase over time. Masking effects are used as a direct measure of prime awareness. Based on their time course, type-A and type-B masking functions are distinguished (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). Type-A masking is most commonly shown with a typically increasing function over time. In contrast, type-B masking functions are rarely observed, which demonstrate a decreasing or u-shaped time course. This masking type is usually only found under metacontrast backward masking (Breitmeyer & Öğmen, 2006; see also Albrecht & Mattler, 2010, 2012, 2016). While priming effects are expected to increase over time by Rapid-Chase Theory (T. Schmidt et al., 2006, 2011; see also T. Schmidt, 2014), the masking effect can show an opposite trend with a decreasing or u-shaped type-B masking curve, forming a double dissociation. In empirical practice, double dissociations are a rarity, while historically simple dissociations have been the favored data pattern to demonstrate perception without awareness, despite suffering from statistical measurement problems (T. Schmidt & Vorberg, 2006). Motivated by this shortcoming, I aim to demonstrate that a double dissociation is the most powerful and convincing data pattern, which provides evidence that visual perception does not necessarily generate visual awareness, since both processes are based on different neuronal mechanisms. I investigated which experimental conditions allow for a double dissociation between priming and prime awareness. The first set of experiments demonstrated that a double-dissociated pattern between priming and masking can be induced artificially, and that the technique of induced dissociations is of general utility. The second set of experiments used two awareness measures (objective vs. subjective) and a response priming task in various combinations, resulting in different task settings (single-, dual-, triple tasks). The experiments revealed that some task types constitute an unfavorable experimental environment that can prevent a double dissociation from occurring naturally, especially when a pure feedforward processing of the stimuli seems to be disturbed. The present work provides further important findings. First, stimulus perception and stimulus awareness show a general dissociability in most of the participants, supporting the idea that different neuronal processes are responsible for this kind of data pattern. Second, any direct awareness measure (no matter whether objective or subjective) is highly observer-dependent, requiring the individual analysis at the level of single participants. Third, a deep analysis of priming effects at the micro level (e.g., checking for fast errors) can provide further insights regarding information processing of different visual stimuli (e.g., shape vs. color) and under changing experimental conditions (e.g. single- vs. triple tasks)

Narcissus to a Man: Lifelogging, Technology and the Normativity of Truth

The growth of the practice of lifelogging, exploiting the capabilities provided by the exponential increase in computer storage, and using technologies such as SenseCam as well as location-based services, Web 2.0, social networking and photo-sharing sites, has led to a growing sense of unease, articulated in books such as Mayer-Schönberger's Delete, that the semi-permanent storage of memories could lead to problematic social consequences. This talk examines the arguments against lifelogging and storage, and argues that they seem less worrying when placed in the context of a wider debate about the nature of mind and memory and their relationship to our environment and the technology we use

The propositional nature of human associative learning

The past 50 years have seen an accumulation of evidence suggesting that associative learning depends oil high-level cognitive processes that give rise to propositional knowledge. Yet, many learning theorists maintain a belief in a learning mechanism in which links between mental representations are formed automatically. We characterize and highlight the differences between the propositional and link approaches, and review the relevant empirical evidence. We conclude that learning is the consequence of propositional reasoning processes that cooperate with the unconscious processes involved in memory retrieval and perception. We argue that this new conceptual framework allows many of the important recent advances in associative learning research to be retained, but recast in a model that provides a firmer foundation for both immediate application and future research