People’s awareness of tactile stimuli has been investigated in far less detail than their awareness of stimuli in other sensory modalities. In an attempt to fill this gap, we provide an overview of studies that are pertinent to the topic of tactile consciousness. We discuss the results of research that has investigated phenomena such as “change blindness”, phantom limb sensations, and numerosity judgments in tactile perception, together with the results obtained from the study of patients affected by deficits that can (...) adversely affect tactile perception such as neglect, extinction, and numbsense. The similarities as well as some of the important differences that have emerged when visual and tactile conscious information processing have been compared using similar experimental procedures are highlighted. We suggest that conscious information processing in the tactile modality cannot be separated completely from the more general processing of spatial information in the brain. Finally, the importance of considering tactile consciousness within the larger framework of multisensory information processing is also discussed. (shrink)

We report two experiments in which participants had to judge the time of occurrence of a stimulus relative to a clock. The experiments were based on the control condition used by Libet, Gleason, Wright, and Pearl [Libet, B., Gleason, C. A., Wright, E. W., & Pearl, D. K. . Time of conscious intention to act in relation to onset of cerebral activities : The unconscious initiation of a freely voluntary act. Brain 106, 623–642] to correct for any bias in the (...) estimation of the time at which an endogenous event, the conscious intention to perform a movement, occurred. Participants’ responses were affected systematically by the sensory modality of the stimulus and by the speed of the clock. Such findings demonstrate the variability in judging the time at which an exogenous event occurs and, by extension, suggest that such variability may also apply to the judging the time of occurrence of endogenous events. The reliability of participants’ estimations of when they formed the conscious intention to perform a movement in Libet et al.’s study is therefore questionable. (shrink)

In timing perception studies, the timing of one event is usually manipulated relative to another, and participants are asked to judge if the two events were synchronous, or to judge which of the two events occurred first. Responses are analyzed to determine a measure of central tendency, which is taken as an estimate of the timing at which the two events are perceptually synchronous. When these estimates do not coincide with physical synchrony, it is often assumed that the sensory signals (...) are asynchronous, as though the transfer of information concerning one input has been accelerated or decelerated relative to the other. Here we show that, while this is a viable interpretation, it is equally plausible that such effects are driven by shifts in the criteria used to differentiate simultaneous from asynchronous inputs. Our analyses expose important ambiguities concerning the interpretation of simultaneity judgement data, which have hitherto been underappreciated. (shrink)

The simultaneous perception of multimodal sensory information is important for effective reactions to the external environment. In relation to the effect on time perception, voluntary movement and rhythmic stimuli have already been identified in previous studies to be associated with improved accuracy of temporal order judgments. Here, we examined whether the combination of voluntary movement and rhythmic stimuli improves the just noticeable difference in audio-tactile TOJ Tasks. Four different experimental conditions were studied, involving two types of movements and two types (...) of stimulus presentation. In the voluntary movement condition, after the auditory stimulus participants moved their right index finger voluntarily and naturally, while in the involuntary movement condition, their right index finger was moved by the tactile device. The stimuli were provided in a rhythmic or one-time only manner by hitting inside the first joint of the participants' right index finger using a tactile device. Furthermore, in the rhythmical tactile conditions, tactile stimuli were presented rhythmically to the right index finger 5 times consecutively. On the other hand, in the one-time tactile conditions, tactile stimuli was presented one-time only to the right index finger. Participants made an order judgment for the fifth tactile stimuli and the first and only auditory stimuli. In our TOJ tasks, auditory-tactile stimulus pairs were presented to participants with varying stimulus-onset asynchronies. For the two stimuli presented at a time that were shifted by the SOA, the participants were asked to judge which one was presented first, and they were given a two-choice answer. Using a non-parametric test, our results showed that voluntary movement and rhythmic tactile stimuli were both effective in improving the JNDs in TOJ Tasks. However, in the combination of voluntary movement and rhythmic tactile stimuli, we found that there was no significant difference in JNDs in our experiments. (shrink)

The rotating spot method of timing subjective events involves the subject’s watching a rotating spot on a computer and reporting the position of the spot at the instant when the subjective event of interest occurs. We conducted an experiment to investigate factors that may impact on the results produced by this method, using the subject’s perception of when they made a simple finger movement as the subjective event to be timed. Seven aspects of the rotating spot method were investigated, using (...) a factorial experiment. Four of these aspects altered the physical characteristics of the computer generated spot or clock face and the remaining three altered the instructions given to the participant. We found compelling evidence that one factor, whether the subject was instructed to report the instant when the finger movement was initiated or the instant when it was completed, resulted in a systematic shift in the response. Evidence that three other factors affect the observed variability in the response was also found. In addition, we observed that there are substantial systematic differences in the responses made by different subjects. We discuss the implications of our findings and make recommendations about the optimal way of conducting future experiments using the rotating spot method. Our overall conclusion is that our results strongly validate the rotating spot method of timing at least the studied variety of subjective event. (shrink)

The law of prior entry was one of E.B. Titchener’s seven fundamental laws of attention. According to Titchener : “the object of attention comes to consciousness more quickly than the objects which we are not attending to.” Although researchers have been studying prior entry for more than a century now, progress in understanding the effect has been hindered by the many methodological confounds present in early research. As a consequence, it is unclear whether the behavioral effects reported in the majority (...) of published studies in this area should be attributed to attention, decisional response biases, and/or, in the case of exogenous spatial cuing studies of the prior-entry effect, to sensory facilitation effects instead. In this article, the literature on the prior-entry effect is reviewed, the confounds present in previous research highlighted, current consensus summarized, and some of the key questions for future research outlined. In particular, recent research has now provided compelling psychophysical and electrophysiological evidence to support the claim that attending to a sensory modality, spatial location, or stimulus feature/attribute can all give rise to a relative speeding-up of the time of arrival of attended, as compared to relatively less attended stimuli. Prior-entry effects have now been demonstrated following both the endogenous and exogenous orienting of attention, though prior-entry effects tend to be smaller in magnitude when assessed by means of participants’ performance on SJ tasks than when assessed by means of their performance on TOJ tasks. (shrink)

Subjects estimated the time of intentions to perform an action, of the action itself, or of an auditory effect of the action. A perceptual attraction or binding effect occurred between actions and the effects that followed them. Judgements of intentions did not show this binding, suggesting they are represented independently of actions and their effects. In additional unpredictable judgement conditions, subjects were instructed only after each trial which of these events to judge, thus discouraging focussed attention to a specific event. (...) Stronger binding effects were found, with intention, action and effect fusing to a single central point in time. In a control task, subjects reported the time of the first or second tone in sequence. Tone sequences showed no binding at all when subjects knew in advance which tone to judge, but showed the same fusion as actions when the event to be judged was not predictable. Binding of actions and effects, but not of tone sequences, occurs pre-attentively, and automatically. The data are consistent with a reconstructive process, implemented after actions, which generates a coherent sense of agency. However, this process should only be triggered only when our actions make it appropriate. We suggest that this mechanism is triggered in advance by efferent processing. This conclusion was supported by a further study in deafferented subject IW. This subject showed the normal binding of a tone towards an action, although his experience of the action was of pre-motor, rather than peripheral origin. The experience of intentional action involves an interplay between pre-motor and reconstructive processes. (shrink)

Psychophysics and neuroscience demonstrate that different sensory systems interact and influence each other. Perceiving involves extensive cooperation and coordination among systems associated with sight, hearing, touch, smell, and taste. Nonetheless, it remains unclear in what respects conscious perceptual awareness is multisensory. This paper distinguishes six differing varieties of multisensory awareness, explicates their consequences, and thereby elucidates the multisensory nature of perception. It argues on these grounds that perceptual awareness need not be exhausted by that which is associated with each of (...) the respective sensory modalities along with whatever accrues thanks to simple co-consciousness. (shrink)

S. Pockett and G. Gomes discuss a possible bias in the method by which Libet's subjects estimated the time at which they became aware of their intent to move their hands. The bias, caused by sensory delay processing the clock information, would be sufficient to alter Trevena and Miller's conclusions regarding the timing of the lateralized readiness potential. I show that the flash-lag effect would compensate for that bias. In the last part of my commentary I note that the other (...) target articles do not examine the most interesting aspect of Libet's unfashionable views on free will. I point out that Libet's views are less strange than they at first appear to be. (shrink)

Benjamin Libet compared the perceived time of direct brain stimulation to the perceived time of skin stimulation. His results are among the most controversial experiments at the interface between psychology and philosophy. The new element that I bring to this discussion is a reanalysis of Libet's raw data. Libet's original data were difficult to interpret because of the manner in which they were presented in tables. Plotting the data as psychometric functions shows that the observers have great uncertainty about the (...) relative timing of events, as seen the shallow psychometric slopes. A second indication of uncertainty comes from Libet's use of three response categories, A first; B first; and A and B simultaneous. The large number of “perceptually simultaneous” responses provides a further measure of the difficulty of the judgment. There are thus a very broad range of stimulus delays in which the subject is unable to make an accurate ordering response. These points provide evidence that there is no compelling reason to invent exotic or ad hoc mechanisms to account for Libet's data since the uncertainty window is large enough to allow simple mechanism such as memory shifts. Libet argued that his data provide evidence for a backward referral in time. I argue that even though Libet's own data are weak, there are good arguments for a backward referral mechanism to help the subject make sense out of the tangled chaos of asynchronous information associated with experienced events. (shrink)

The temporal granularity of consciousness may be far less fine than the real-time information processing mechanisms that underlie our sensitivity to small temporal differences. It is suggested that conscious time perception, like space perception, is subject to errors that belie a unitary underlying representation. E. R. Clay's concept of the “specious present,” an extended moment represented in consciousness, is suggested as an alternative to the more common notion of instantaneous experience that underlies much reasoning based on the “time of arrival” (...) in consciousness. (shrink)

In my dissertation I critically survey existing theories of time consciousness, and draw on recent work in neuroscience and philosophy to develop an original theory. My view depends on a novel account of temporal perception based on the notion of temporal qualities, which are mental properties that are instantiated whenever we detect change in the environment. When we become aware of these temporal qualities in an appropriate way, our conscious experience will feature the distinct temporal phenomenology that is associated with (...) the passing of time. The temporal qualities model of perception makes two predictions about the mechanisms of time perception; one that time perception is modality specific and the other that it can occur without awareness. My argument for this view partially depends on a number of psychophysical experiments that I designed and implemented myself and which investigate subjective time distortions caused by looming visual stimuli. These results show that the mechanisms of conscious experience of time are distinct from the mechanisms of time perception, as my theory of temporal qualities predicts. (shrink)

According to rich views of consciousness (e.g., James, Searle), we have a constant, complex flow of experience (or 'phenomenology') in multiple modalities simultaneously. According to thin views (e.g., Dennett, Mack and Rock), conscious experience is limited to one or a few topics, regions, objects, or modalities at a time. Existing introspective and empirical arguments on this issue (including arguments from 'inattentional blindness') generally beg the question. Participants in the present experiment wore beepers during everyday activity. When a beep sounded, they (...) were to take note of the conscious experience, if any, they were having at the last undisturbed moment immediately prior to the beep. Some participants were asked to report any experience they could remember. Others were asked simply to report whether there was visual experience or not (and if so, what it was). Still others were asked about experience in the far right visual field, or tactile experience, or tactile experience in the left foot. A majority of participants in the full experience and the visual conditions reported visual experience in every single sample. Tactile and peripheral visual experience were reported less often. However, the proper interpretation of these results is uncertain. (shrink)

The thesis that consists of three studies investigated how visual affective stimuli or action as contexts influence crossmodal time processing, particularly on the role of the crossmodal/sensorimotor linkage in time perception. By using different types of emotional stimuli and manipulating the possibility of near-body interactions, three studies disassociated the impacts of embodied action from emotional dimensions on crossmodal emotional modulation in time perception. The whole thesis thus offered the first behavioral evidence that embodied action is an important factor that expands (...) subjective tactile duration and facilitates tactile selection in emotion and action contexts. Moreover, subjective expansion of duration by threat and action contexts may reflect the evolutionary coupling of our perceptual and motor systems to adapt to the specific environments for survival and success. (shrink)