Is perceptual space inherently non-Euclidean?

It is often assumed that the space we perceive is Euclidean, although this idea has been challenged by many authors. Here we show that if spatial cues are combined as described by Maximum Likelihood Estimation, Bayesian, or equivalent models, as appears to be the case, then Euclidean geometry cannot describe our perceptual experience. Rather, our perceptual spatial structure would be better described as belonging to an arbitrarily curved Riemannian space.     

Is there a constant minimum perceptual duration?

It has been suggested in the recent literature that all stimuli briefer than a critical duration have identical perceptual durations. Relevant simultaneity, reaction time, temporal order and duration discrimination data are discussed, and new data are presented. It is concluded that the relationship between the physical duration of a stimulus and its perceptual duration is not yet understood.     

Is color “categorical perception” really perceptual?

Roberson and Davidoff (2000) found that color categorical perception (CP; better cross-category than within-category discrimination) was eliminated by verbal, but not by visual, interference presented during the interstimulus interval (ISI) of a discrimination task. On the basis of this finding, Roberson and Davidoff concluded that CP was mediated by verbal labels, and not by perceptual mechanisms, as is generally assumed. Experiment 1 replicated their results. However, it was found that if the interference type was uncertain on each trial (Experiment 2), CP then survived verbal interference. Moreover, it was found that the target color name could be retained across the ISI even with verbal interference (Experiment 3). We therefore conclude that color CP may indeed involve verbal labeling but that verbal interference does not necessarily prevent it.     

Is predictive processing a theory of perceptual consciousness?

Predictive Processing theory, hotly debated in neuroscience, psychology and philosophy, promises to explain a number of perceptual and cognitive phenomena in a simple and elegant manner. In some of its versions, the theory is ambitiously advertised as a new theory of conscious perception. The task of this paper is to assess whether this claim is realistic. We will be arguing that the Predictive Processing theory cannot explain the transition from unconscious to conscious perception in its proprietary terms. The explanations offered by PP theorists mostly concern the preconditions of conscious perception, leaving the genuine material substrate of consciousness untouched.     

Is judgment of random time intervals biased and capacity-limited?

 Recently, random generation of time intervals has been proposed as a procedure to impair executive processing in a dual-task paradigm without substantial interference with phonological and visuo-spatial working memory resources. A fundamental assumption of this procedure is that humans are able to distinguish time sequences on their degree of randomness. The present study tests this assumption. To this end, non-biased, repetition-biased, alternation-biased sequences and repetitive rhythms were judged under conditions of higher or lower executive load. In Exp. 1, load depended on the presentation speed, while in Exp. 2, a dual-task condition was used with either a concurrent number-copying task or an arithmetic task. It was found that the participants could distinguish repetitive rhythms from more or less random sequences, and that both accuracy of this judgment and latency were affected by the concurrent load. The findings are taken as a first indication that random time judgment is capacity-limited. Received: 9 September 1999 / Accepted: 1 October 1999     

Is desynchrony tolerance adaptable in the perceptual organization of speech?

Speech signal components that are desynchronized from the veridical temporal pattern lose intelligibility. In contrast, audiovisual presentations with large desynchrony in visible and audible speech streams are perceived without loss of integration. Under such conditions, the limit of desynchrony that permits audiovisual integration is also adaptable. A new project directly investigated the potential for adaptation to consistent desynchrony with unimodal auditory sine-wave speech. Listeners transcribed sentences that are highly intelligible, with veridical temporal properties. Desynchronized variants were created by leading or lagging the tone analog of the second formant relative to the rest of the tones composing the sentences, in 50-msec steps, ranging from 250-msec lead to 250-msec lag. In blocked trials, listeners only tolerated desynchronies <50 msec, and exhibited no gain in intelligibility to consistent desynchrony. Unimodal auditory and bimodal audiovisual forms of perceptual integration evidently exhibit different temporal characteristics, an indication of distinct perceptual functions.     

Is perceptual salience needed in explanations of the isolation effect?

The isolation effect is a well-known phenomenon that has a well-accepted explanation: An item that is isolated on a list becomes perceptually salient, which leads to extra rehearsal that enhances memory for the isolate. To evaluate this hypothesis, the authors isolated an item near the beginning of a list. Immediately after each item was presented for study, participants judged the likelihood of recalling the item. Although the isolation effect occurred, participants did not judge the isolate as being more memorable than the preceding item, suggesting that the isolate was not salient. In a second experiment, participants rehearsed items aloud. Isolation at the beginning of the list did not produce extra rehearsal. By contrast, isolation in the middle of the list produced extra rehearsal; however, even when the isolate did not receive extra rehearsal, an isolation effect was evident. Thus, salience and extra rehearsal are not necessary for producing an isolation effect.     

Is hefting to perceive the affordance for throwing a smart perceptual mechanism?

G. P. Bingham, R. C. Schmidt, and L. D. Rosenblum (1989) found that, by hefting objects of different sizes and weights, people could choose the optimal weight in each size for throwing to a maximum distance. In Experiment 1, the authors replicated this result. G. P. Bingham et al. hypothesized that hefting is a smart mechanism that allows objects to be perceived in the context of throwing dynamics. This hypothesis entails 2 assumptions. First, hefting by hand is required for information about throwing by hand. The authors tested and confirmed this in Experiments 2 and 3. Second, optimal objects are determined by the dynamics of throwing. In Experiment 4, the authors tested this by measuring throwing release angles and using them with mean thrown distances from Experiment 1 and object sizes and weights to simulate projectile motion and recover release velocities. The results showed that only weight, not size, affects throwing. This failed to provide evidence supporting the particular smart mechanism hypothesis of G. P. Bingham et al. Because the affordance relation is determined in part by the dynamics of projectile motion, the results imply that the affordance is learned from knowledge of results of throwing.     

Symbolic comparisons with and without perceptual referents: Is interval information used?

In an attempt to investigate the range effect obtained by Moyer and Bayer (1976), two groups of subjects were taught to associate colors with circles that differed in size by larger or smaller intervals and then participated in a symbolic comparison task, in which they determined which of two simultaneously presented symbols (the first letters of two colors) represented the larger magnitude. A third group of subjects, who merely learned an arbitrary ordering of the colors along the dimension of size, also participated in the symbolic comparison task. Despite the fact that no practice trials were given, there was no effect of interval size in either early or late blocks, and the circle-learning groups did not differ in performance from the group who only learned an arbitrary ordering of colors, even when pairs containing end terms were removed from the analysis. It is concluded that subjects do not use analogue codes in symbolic comparison tasks involving small, repeated sets of arbitrarily defined symbols.     

Must boxing verdicts be biased?

A model of judgment made by sports judges is outlined. Its main assumptions are as follows. (1) From the beginning a judge tries to form a hypothesis about which of the two competitors should be awarded the victory. (2) The advantages of both competitors are assessed, and these values are changed according to successive observations. (3) However, the meanings assigned to successive actions are not impartial: the greater the initial advantage of one competitor, the more his gains are enhanced and his losses de-emphasized. Both statistical analysis of judgments made at a boxing championship and in a special experiment with boxing judges revealed several regularities which seem to fit the outlined model, including a pervasive primacy effect. This effect seems to be a consequence of early preselection of the potential winner and a subsequent one-sided processing of sequentially presented information. Possible ways of avoiding partiality in boxing assessments are briefly discussed.     

Are there unconscious perceptual processes?

Blindsight and vision for action seem to be exemplars of unconscious visual processes. However, researchers have recently argued that blindsight is not really a kind of unconscious vision but is rather severely degraded conscious vision. Morten Overgaard and colleagues have recently developed new methods for measuring the visibility of visual stimuli. Studies using these methods show that reported clarity of visual stimuli correlates with accuracy in both normal individuals and blindsight patients. Vision for action has also come under scrutiny. Recent findings seem to show that information processed by the dorsal stream for online action contributes to visual awareness. Some interpret these results as showing that some dorsal stream processes are conscious visual processes (e.g., Gallese, 2007; Jacob & Jeannerod, 2003). The aim of this paper is to provide new support for the more traditional view that blindsight and vision for action are genuinely unconscious perceptual processes. I argue that individuals with blindsight do not have access to the kind of purely qualitative color and size information which normal individuals do. So, even though people with blindsight have a kind of cognitive consciousness, visual information processing in blindsight patients is not associated with a distinctly visual phenomenology. I argue further that while dorsal stream processing seems to contribute to visual awareness, only information processed by the early dorsal stream (V1, V2, and V3) is broadcast to working memory. Information processed by later parts of the dorsal stream (the parietal lobe) never reaches working memory and hence does not correlate with phenomenal awareness. I conclude that both blindsight and vision for action are genuinely unconscious visual processes.     

Post-cueing after erasure of the icon: Is there a set effect?

Recognition accuracy in a tachistoscopic identification task typically declines as the size of the set from which the target was selected increases. To determine whether this effect is due to selective encoding from iconic store, a masking stimulus, intended to erase the icon, was presented following the stimulus. Information about the set was then presented. It was found that subjects' performance in this post-cueing situation did not differ from performance in a pre-cueing condition, where the set was presented prior to the stimulus. It was concluded that set size does not have its effect through selective encoding from iconic store. Results were discussed in terms of the fragment theory.     

Are young children's drawings canonically biased?

In a between-subjects design, 4- to 6-year-olds were asked to draw from three-dimensional (3D) models, two-and-a-half-dimensional (212D) models with or without depth cues, or two-dimensional (2D) models of a familiar object (a saucepan) in noncanonical orientations (handle at the back or at the front). Results showed that canonical errors were produced mainly by the youngest children in the 3D models copying condition. A large proportion of errors did not, however, reflect biases toward the participants' "own" view of the object; rather, these errors reflected biases toward their "best" view of the object. Drawing from models having fewer than three dimensions resulted in a significant increase in view-specific productions in all children for the back orientation. When a more complex front orientation of the object was proposed, sensitivity to model type developed gradually with age. Results are discussed in terms of the flexibility of the mental model that mediates between children's perception of a model object and the depiction decisions.     

Do looks constitute our perceptual evidence?

Many philosophers take experience to be an essential aspect of perceptual justification. I argue against a specific variety of such an experientialist view, namely, the Looks View of perceptual justification, according to which our visual beliefs are mediately justified by beliefs about the way things look. I describe three types of cases that put pressure on the idea that perceptual justification is always related to looks‐related reasons: unsophisticated cognizers, multimodal identification, and amodal completion. I then provide a tentative diagnosis of what goes wrong in the Looks View: it ascribes a specific epistemic role to beliefs about looks that is actually fulfilled by subpersonal perceptual processes.     

Does perceptual belongingness affect lightness constancy?

The relation between perceptual belongingness and lightness perception has historically been studied in the contrast domain (Benary, 1924 Psychologische Forschung 5 131 - 142). However, scientists have shown that two equal grey patches may differ in lightness when belonging to different reflecting surfaces. We extend this investigation to the constancy domain. In a CRT simulation of a bipartite field of illumination, we manipulated the arrangement of twelve patches: six squares and six diamonds. Patches of the same shape could be placed: (i) all within the same illumination field; or (ii) forming a row across the illumination fields. Furthermore, we manipulated proximity between the innermost patches and the illumination edge. The patches could be (i) touching (forming an X-junction); or (ii) not touching (not forming an X-junction). Observers were asked to perform a lightness match between two additional patches, one illuminated and the other in shadow. We found better lightness constancy when the patches of the same shape formed a row across the fields, with no effect of X-junctions. Since lightness constancy is improved by strengthening the belongingness across the illumination fields, we conclude that belongingness might help the visual system to aggregate the differently illuminated surfaces, and facilitate the scission process.     

Why do we need perceptual content?

Most representationalists argue that perceptual experience has to be representational because phenomenal looks are, by themselves, representational. Charles Travis (2004 Travis, C. (2004). The silence of the senses. Mind, 113, 57–94.[Crossref], [Web of Science ®] , [Google Scholar]) argues that looks cannot represent. I argue that perceptual experience has to be representational due to the way the visual system works.     

A common oscillator for perceptual rivalries?

Perceptual rivalry is an oscillation of conscious experience that takes place despite univarying. if ambiguous, sensory input. Much current interest is focused on the controversy over the neural site of binocular rivalry, a variety of perceptual rivalry for which a number of different cortical regions have been implicated. Debate continues over the relative role of higher levels of processing compared with primary visual cortex and the suggestion that different forms of rivalry involve different cortical areas. Here we show that the temporal pattern of disappearance and reappearance in motion-induced blindness (MIB) (Bonneh et al, 2001 Nature 411 798-801) is highly correlated with the pattern of oscillation reported during binocular rivalry in the same individual. This correlation holds over a wide range of inter-individual variation. Temporal similarity in the two phenomena was strikingly confirmed by the effects of the hallucinogen LSD, which produced the same, extraordinary, pattern of increased rhythmicity in both kinds of perceptual oscillation. Furthermore. MIB demonstrates the two properties previously considered characteristic of binocular rivalry. Namely the distribution of dominance periods can be approximated by a gamma distribution and, in line with Levelt's second proposition of binocular rivalry, predominance of one perceptual phase can be increased through a reduction in the predominance time of the opposing phase. We conclude that (i) MIB is a form of perceptual rivalry, and (ii) there may be a common oscillator responsible for timing aspects of all forms of perceptual rivalry.