Dissolving an epistemological puzzle of time perception

Robin Le Poidevin (2007) claims that we do form perceptual beliefs regarding order and duration based on our perception of events, but neither order nor duration are by themselves objects of perception. Temporal properties are discernible only when one first perceives their bearers, and temporal relations are discernible only when one first perceives their relata. The epistemic issue remains as to whether or not our perceptual beliefs about order and duration are formed on the causal basis of an event’s objective order and duration. Le Poidevin raises this issue in the form of an epistemological puzzle of time perception, from which he derives the claim that the order and duration of events do not causally contribute to our perceptual beliefs about them. Since his view is motivated by a causal truthmaker principle for grounding knowledge, it also holds that perceptual beliefs about temporal features must be caused by the features themselves in order to count as knowledge. Given these theoretical commitments, there is a puzzle concerning how such perceptual beliefs could constitute knowledge of temporal properties. In response to Le Poidevin, I argue for an account according to which order and duration are objects of perception, causally contribute to our perceptual beliefs about them, and such beliefs are capable of counting as knowledge. I conclude by showing that, on my alternative account, the epistemological puzzle dissolves and his own solution to it fails.     

Visual parsing and priority effects in temporal order judgements of line drawn patterns

Five experiments are reported in which the perception of the order of the components of line drawn patterns presented in rapid temporal sequence on a visual display unit was investigated. In experiments 1 and 2, respectively, a schematic face and an asymmetrical geometric design, and a realistic face and a symmetrical geometric design were each divided into four fragments consisting of outline and three internal features. These fragments were presented to observers in sequences in which the position of the outline in the sequence was systematically varied. Observers reported the perceived order of the fragments. If the order was misperceived the interfragment interval was increased until the sequence was correctly perceived. Analysis of the pattern of perceptual errors and the interfragment presentation interval at which the sequence was correctly perceived indicated that observers tended to perceive the sequence correctly when the outline was presented in first or last position, but had difficulty in doing this when it occupied an intermediate position. This effect was significantly stronger with facial than with geometric patterns. Furthermore, in the case of two face patterns, errors were of a form where observers reported the outline presented in positions two or three as occupying positions one or four respectively. In experiment 3 an identical procedure was used to compare the perception of temporally fragmented normal and inverted faces. The outline position effect was equally strong in both cases. In experiment 4 the relative strength of the tendency to move the outline towards first or final position was assessed by dividing each of two patterns, a face and a house, into three fragments consisting of outline and two groups of internal features. Order perception was significantly better with outline in first or third position, but where it was presented in the intermediate position it was reported as being presented in first position. In experiment 5 the general pattern of results obtained in experiments 1, 2, and 3 was verified with the use of a methodology in which pattern fragment sequences and interfragment intervals were both randomised from trial to trial and the observer's task was to specify the position of the outline in the sequence. Four patterns--a normal face, a face with inverted internal features (INF face), a face outline with irrelevant internal features (IRF face), and a geometric design--were each divided into four fragments consisting of outline and three internal features.(ABSTRACT TRUNCATED AT 400 WORDS)     

Perceptual organization of apparent motion in the Ternus display

A typical Ternus display has three sequentially presented frames, in which frame 1 consists of three motion tokens, frame 2 (blank) defines the interstimulus interval, and frame 3 has similar motion tokens with their relative positions shifted to the right. Interestingly, what appears to be a seemingly simple arrangement of stimuli can induce one of two distinct apparent-motion percepts in the observer. The first is an element-motion perception where the left-end token is seen to jump over its two neighboring tokens (inner tokens) to the right end of the display. The second is a group-motion perception where the entire display of the three tokens is seen to move to the right. How does the visual system choose between these two apparent-motion perceptions? It is hypothesized that the choice of motion perception is determined in part by the perceptual organization of the motion tokens. Specifically, a group-motion perception is experienced when a strong grouping tendency exists among the motion tokens belonging to the same frame. Conversely, an element-motion perception is experienced when a strong grouping tendency exists between the inner motion tokens in frames 1 and 3 (i.e. the two tokens that overlap in space between frames). We tested this hypothesis by varying the perceptual organization of the motion tokens. Both spatial (form similarity, 3-D proximity, common surface/common region, and occlusion) and temporal (motion priming) factors of perceptual organization were tested. We found that the apparent-motion perception of the Ternus display can be predictably affected, in a manner consistent with the perceptual organization hypothesis.     

Two Conceptions of Conceptualism and Nonconceptualism

Though it enjoys widespread support, the claim that perceptual experiences possess nonconceptual content has been vigorously disputed in the recent literature by those who argue that the content of perceptual experience must be conceptual content. Nonconceptualism and conceptualism are often assumed to be well-defined theoretical approaches that each constitute unitary claims about the contents of experience. In this paper I try to show that this implicit assumption is mistaken, and what consequences this has for the debate about perceptual experience. I distinguish between two different ways that nonconceptualist (and conceptualist) proposals about perceptual content can be understood: as claims about the constituents that compose perceptual contents or as claims about whether a subject’s undergoing experiences with those contents requires them to possess the concepts that characterize those contents. I maintain that these ways of understanding conceptualism and nonconceptualism are orthogonal to one another. This is revealed by the conceptual coherence of positions in which the contents of experiences have both conceptual and nonconceptual features; positions which possess their own distinctive sources of philosophical motivation. I argue that the fact that there is a place in conceptual space for such positions, and that there may be good reason for theorists to adopt them, creates difficulties for both the central argument for nonconceptualism and the central argument for conceptualism. I set out each of these arguments; the Argument from Possession-Independence and the Epistemically-Driven Argument. I then try to show how the existence of mixed positions about perceptual content derived from a clear distinction between compositional and possessional considerations constitutes a significant obstacle for those arguments as they stand. The takehome message of the paper is that unless one clearly acknowledges the distinction between issues about the composition of perceptual content and issues about how subject’s capacities to undergo certain experiences relates to their possession of concepts one runs the risk of embracing unsatisfying philosophical arguments in which conclusions relevant to one conception of nonconceptual and conceptual content are grounded on arguments that concern only the other; arguments that cannot, in themselves, sustain them.     

Temporal preparation facilitates perceptual identification of letters

Recent evidence has suggested that perceptual processing of single stimulus features improves when participants are temporally prepared for the occurrence of the stimuli. This study was conducted to investigate whether the benefit of temporal preparation generalizes to perceptual identification of more complex stimuli, such as letters. In three experiments, participants discriminated masked letters under high- and low-temporal-preparation conditions. Visual discrimination performance in all experiments improved when the participants were temporally prepared. Therefore, the present results support the notion that perception benefits from temporal preparation not only at the feature level, but also at subsequent levels at which feature information is integrated.     

Motor Intentionality and its Primordiality

Is intentionality possible without representation? This paper considers the conditions under which intentionality without representation could occur and what sort of perceptual content such intentionality would have. In addition, it considers the constraints on non‐representational intentional content in organisms that have representation. The paper is divided into three parts. The first section compares and contrasts two opposed positions on non‐representational intentionality, those of Herbert Dreyfus and John Searle. The second section reviews a neurobiological model that accommodates the possibility of non‐representational perceptual content. The final section provides a puzzle for theories of non‐representational perceptual content, specifically in connection with the perception of representations. The puzzle of representation and perception illustrates a further need for all theories of perception, both philosophical and scientific: to provide a more finely developed definition of the notion of representation.     

Feature-based attention influences later temporal perception

We investigated the influence of feature-based visual attention on later temporal perception. Although there is ample evidence that space-based attention modulates temporal perception, it is not known whether feature-based attention also serves this function. The present study combined a visual selection task with a temporal interval production task to determine whether feature-based attention interacted with temporal perception. The results indicated that temporal perception of visual stimuli depended on whether the same stimulus had been attended to or ignored in a previous visual selection task. The temporal production of previously ignored stimuli was longer than the temporal production of either previously attended to or novel stimuli. This is the first demonstration of the effect of feature-based attention on later temporal perception. We concluded that temporal perception is affected by previously ignored stimuli.     

The Ontology of Perception: Bipolarity and Content

The notion of perceptual content is commonly introduced in the analysis of perception. It stems from an analogy between perception and propositional attitudes. Both kinds of mental states, it is thought, have conditions of satisfaction. I try to show that on the most plausible account of perceptual content, it does not determine the conditions under which perceptual experience is veridical. Moreover, perceptual content must be bipolar (capable of being correct and capable of being incorrect), whereas perception as a mental state is not (if it is veridical, it is essentially so). This has profound consequences for the epistemological view that perception is a source of knowledge. I sktech a two-level epistemology which is consistent with this view. I conclude that the analogy between perception and propositional attitudes, from which the notion of perceptual content is born, may be more misleading than it is usually thought. This revised version was published online in August 2006 with corrections to the Cover Date.     

网络词语与非网络词语的知觉差异:时间知觉、空间距离知觉与知觉范围

根据具身认知理论,人们的认知会受到身体活动的影响。网络环境下人的身体活动受到限制,因而其认知活动与非网络环境存在很大的差异。本研究目的在于考察人们对网络词语与非网络的日常词语的时间知觉,空间距离知觉与知觉范围是否有差异。结果发现被试对网络词语的时间知觉更长;网络词语的空间距离感与日常词语没有显著差异;在启动网络词语之后,被试的知觉范围缩小,对中心刺激的反应显著快于边缘刺激。本研究发现了网络词语加工在时间知觉和知觉范围上的变化。     

Biases in the perceived timing of perisaccadic perceptual and motor events

Subjects typically experience the temporal interval immediately following a saccade as longer than a comparable control interval. One explanation of this effect is that the brain antedates the perceptual onset of a saccade target to around the time of saccade initiation. This could explain the apparent continuity of visual perception across eye movements. This antedating account was tested in three experiments in which subjects made saccades of differing extents and then judged either the duration or the temporal order of key events. Postsaccadic stimuli underwent subjective temporal lengthening and had early perceived onsets. A temporally advanced awareness of saccade completion was also found, independently of antedating effects. These results provide convergent evidence supporting antedating and differentiating it from other temporal biases.     

The effect of false memory on temporal perception

This study examined the effect of false memory on temporal perception. The Deese-Roediger-McDermott (DRM) paradigm, which elicits false recognition of a nonpresented word, was used to determine whether the perceived duration of falsely remembered words was longer than that for control words. The study results revealed that the perceived duration for falsely recognized words was longer than that for correctly rejected words. This is the first study to show the effect of false memory on temporal perception and suggests that temporal perception can be affected by conceptual fluency without any perceptual repetition.     

Perceptual processing of natural scenes at rapid rates: Effects of complexity, content, and emotional arousal

During rapid serial visual presentation (RSVP), the perceptual system is confronted with a rapidly changing array of sensory information demanding resolution. At rapid rates of presentation, previous studies have found an early (e.g., 150–280 ms) negativity over occipital sensors that is enhanced when emotional, as compared with neutral, pictures are viewed, suggesting facilitated perception. In the present study, we explored how picture composition and the presence of people in the image affect perceptual processing of pictures of natural scenes. Using RSVP, pictures that differed in perceptual composition (figure–ground or scenes), content (presence of people or not), and emotional content (emotionally arousing or neutral) were presented in a continuous stream for 330 ms each with no intertrial interval. In both subject and picture analyses, all three variables affected the amplitude of occipital negativity, with the greatest enhancement for figure–ground compositions (as compared with scenes), irrespective of content and emotional arousal, supporting an interpretation that ease of perceptual processing is associated with enhanced occipital negativity. Viewing emotional pictures prompted enhanced negativity only for pictures that depicted people, suggesting that specific features of emotionally arousing images are associated with facilitated perceptual processing, rather than all emotional content.     

Asymmetries in visuomotor recalibration of time perception: Does causal binding distort the window of integration?

The recalibration of perceived visuomotor simultaneity to vision-lead and movement-lead temporal discrepancies is marked by an underlying causal asymmetry, if the movement (button press) is voluntary and self-initiated; a visual stimulus lagging the button press may be interpreted as causally linked sensory feedback (intentional or causal binding), a leading visual stimulus not. Here, we test whether this underlying causal asymmetry leads to directional asymmetries in the temporal recalibration of visuomotor time perception, using an interval estimation paradigm. Participants were trained to the presence of one of three temporal discrepancies between a motor action (button press) and a visual stimulus (flashed disk): 100 ms vision-lead, simultaneity, and 100 ms movement-lead. By adjusting a point on a visual scale, participants then estimated the interval between the visual stimulus and the button press over a range of discrepancies. Comparing the results across conditions, we found that temporal recalibration appears to be implemented nearly exclusively on the movement-lead side of the range of discrepancies by a uni-lateral lengthening or shortening of the window of temporal integration. Interestingly, this marked asymmetry does not lead to a significantly asymmetrical recalibration of the point of subjective simultaneity or to significant differences in discriminability. This seeming contradiction (symmetrical recalibration of subjective simultaneity and asymmetrical recalibration of interval estimation) poses a challenge to common models of temporal order perception that assume an underlying time measurement process with Gaussian noise. Using a two-criterion model of the window of temporal integration, we illustrate that a compressive bias around perceived simultaneity (temporal integration) even prior to perceptual decisions about temporal order would be very hard to detect given the sensitivity of the psychophysical procedures commonly used.     

The Non-conceptual Content of Perceptual Experience: Situation Dependence and Fineness of Grain

I begin by examining a recent debate between John McDowell and Christopher Peacocke over whether the content of perceptual experience is non-conceptual. Although I am sympathetic to Peacocke's claim that perceptual content is non-conceptual, I suggest a number of ways in which his arguments fail to make that case. This failure stems from an over-emphasis on the "fine-grainedness" of perceptual content -a feature that is relatively unimportant to its non-conceptual structure. I go on to describe two other features of perceptual experience that are more likely to be relevant to the claim that perceptual content is non-conceptual. These features are 1) the dependence of a perceived object on the perceptual context in which it is perceived and 2) the dependence of a perceived property on the object it is perceived to be a property of.     

Transient sex differences during adolescence on auditory perceptual tasks

Many perceptual abilities differ between the sexes. Because these sex differences have been documented almost exclusively in adults, they have been attributed to sex‐specific neural circuitry that emerges during development and is maintained in the mature perceptual system. To investigate whether behavioral sex differences in perception can also have other origins, we compared performance between males and females ranging in age from 8 to 30 years on auditory temporal‐interval discrimination and tone‐in‐noise detection tasks on which there are no sex differences in adults. If sex differences in perception arise only from the establishment and subsequent maintenance of sex‐specific neural circuitry, there should be no sex differences during development on these tasks. In contrast, sex differences emerged in adolescence but resolved by adulthood on two of the six conditions, with signs of a similar pattern on a third condition. In each case, males reached mature performance earlier than females, resulting in a sex difference in the interim. These results suggest that sex differences in perception may arise from differences in the maturational timing of common circuitry used by both sexes. They also imply that sex differences in perceptual abilities may be more prevalent than previously thought based on adult data alone.     

知觉组织对时序知觉的双重影响:同时判断任务的证据

本研究探讨知觉组织对时序知觉的双重影响。实验采用三条线段构成的C形为实验材料,操纵图形朝向和SOA水平(实验1和实验2)、图形颜色(实验3)以及反应限制(实验4),要求被试完成同时判断任务。结果发现,在不同的SOA条件下,图形对向条件的同时判断频率均显著高于图形反向条件(实验1),即使在知觉组织线索弱化时这种现象仍然存在(实验2和实验3),而且知觉组织对时序知觉的影响不是由于被试的反应偏向导致的(实验4)。结果说明知觉组织对时序知觉存在双重影响:当两个刺激同时出现时,知觉组织能够提高时序知觉表现; 而当两个刺激非同时出现时,知觉组织显著降低时序知觉表现。     

Effects of interval duration on temporal processing in schizophrenia

INTRODUCTION: Temporal processing has received scant attention in the literature pertaining to cognitive deficits in patients with schizophrenia. Previous research suggests that patients with schizophrenia exhibit temporal perception deficits on both auditory and visual stimuli. The current study investigated the effects of interval manipulation to (1) replicate the original findings with a larger sample and an increased number of trials (2) assess the degree to which both patients and controls can differentiate temporal changes in a range of experimental interstimulus intervals, and (3) explore whether different interstimulus interval durations pose different levels of difficulty for the patients with schizophrenia. METHODS: Participants were asked to decide whether temporal intervals were shorter or longer than standard intervals on a computer-based auditory temporal perception task. The standard interval remained the same duration throughout the various tasks. The interstimulus interval separating the standard and experimental intervals varied in the range of 500, 1000, or 3000 ms. Data are presented for a sample of 16 patients with schizophrenia and 15 controls. RESULTS: Data suggest that patients with schizophrenia exhibit deficits in differentiating interval durations across all paradigms compared to their control-group peers on a range of auditory tasks (p<.001). CONCLUSIONS: These results are consistent with a general temporal deficit in schizophrenia. However, the roles of medication and localization are also addressed.     

听觉丧失对听障学生时间知觉的影响

本研究采用同时判断任务和时距二分任务,探讨了听觉丧失对听障学生视觉通道的时间知觉的影响及其机制。两个系列实验结果表明,听觉丧失损伤了听障学生视觉通道的时序知觉准确性、敏感性以及时距知觉的敏感性,支持了普遍缺陷假设;但是,听障学生视觉通道的时距知觉的准确性却未受到听觉丧失的显著影响,支持了知觉补偿假设。因此,听觉丧失对听障学生视觉通道的时间知觉的影响可能是基于选择性的机制,这主要取决于不同的时间任务以及知觉属性等因素。     

The temporal dynamics of the perceptual consequences of action-effect prediction

An essential aspect of voluntary action control is the ability to predict the perceptual effects of our actions. Although the influence of action-effect prediction on humans’ behavior and perception is unequivocal, it remains unclear when action-effect prediction is generated by the brain. The present study investigates the dynamics of action effect anticipation by tracing the time course of its perceptual consequences. Participants completed an acquisition phase during which specific actions (left and right key-presses) were associated with specific visual effects (upward and downward dots motion). In the test phase they performed a 2 AFC identification task in which they were required to indicate whether the dots moved upward or downward. To isolate any effects of action-effect prediction on perception, participants were presented with congruent and incongruent dot motion in which the association participants learned in the previous acquisition phase was respected and violated, respectively. Crucially, to assess the temporal dynamics of action prediction, congruent and incongruent stimuli were presented at different intervals before or after action execution. We observed higher sensitivity (d′) to motion discrimination in congruent vs. incongruent trials only when stimuli were presented from about 220 ms before the action to 280 ms after the action. The temporal dynamics of our effect suggest that action-effect prediction modulates perception at later stages of motor preparation.     

Consequences of Ethical Relativism

The aim of this paper is to investigate the temporal content of perceptual experience. I argue for a view according to which we must recognize the existence of perceptions the content of which cannot be spelled out simply by looking at what is the case at an isolated instant. Acts of apprehension can cover a succession of events. Howev er, a subject who has such perceptions can still fall short of having a concept of time. I compare this with arguments which have been put forward to show that a subject who has spatial perceptions can fall short of having a concept of space. In both cases, it is the fact that perception is from a point of view which stands in the way of it constituting an exercise of a concept of how things are objectively. However, I also show that the way in which perception is perspectival takes a different form in each of the two cases.