Top-down resolution of visual ambiguity – knowledge from the future or footprints from the past?

Current theories about visual perception assume that our perceptual system weights the a priori incomplete, noisy and ambiguous sensory information with previous, memorized perceptual experiences in order to construct stable and reliable percepts. These theories are supported by numerous experimental findings. Theories about precognition have an opposite point of view. They assume that information from the future can have influence on perception, thoughts, and behavior. Several experimental studies provide evidence for precognition effects, other studies found no such effects. One problem may be that the vast majority of precognition paradigms did not systematically control for potential effects from the perceptual history. In the present study, we presented ambiguous Necker cube stimuli and disambiguated cube variants and systematically tested in two separate experiments whether perception of a currently observed ambiguous Necker cube stimulus can be influenced by a disambiguated cube variant, presented in the immediate perceptual past (perceptual history effects) and/or in the immediate perceptual future (precognition effects). We found perceptual history effects, which partly depended on the length of the perceptual history trace but were independent of the perceptual future. Results from some individual participants suggest on the first glance a precognition pattern, but results from our second experiment make a perceptual history explanation more probable. On the group level, no precognition effects were statistically indicated. The perceptual history effects found in the present study are in confirmation with related studies from the literature. The precognition analysis revealed some interesting individual patterns, which however did not allow for general conclusions. Overall, the present study demonstrates that any future experiment about sensory or extrasensory perception urgently needs to control for potential perceptual history effects and that temporal aspects of stimulus presentation are of high relevance.

The Certainty of Ambiguity in Visual Neural Representations

Some images evoke bistable percepts: two different visual experiences seen in alternation while continuously viewing an unchanged stimulus. The Necker Cube and Rubin's Vase are classic examples, each of which gives alternating percepts of different shapes. Other bistable percepts are alternating colors or directions of motion. Although stimuli that result in salient bistability are rare and sometimes cleverly constructed to emphasize ambiguity, they have been influential for over 150 years, since the work of von Helmholtz, who considered them to be evidence for perceptual visual processes that interpret retinal stimuli. While bistability in natural viewing is uncommon, the main point of this review is that implicit ambiguity in visual neural representations is pervasive. Resolving ambiguity, therefore, is a fundamental and ubiquitous process of vision that routinely affects what we see, not an oddity arising from cleverly crafted images. This review focuses on the causes of widespread ambiguity, historical perspectives on it, and modern knowledge and theory about resolving it.

Investigating racing thoughts via ocular temporal windows: deficits in the control of automatic perceptual processes

Background Racing thoughts have been found in several states of bipolar disorder (BD), but also in healthy populations with subclinical mood alterations. The evaluation of racing thoughts relies on subjective reports, and objective measures are sparse. The current study aims at finding an objective neuropsychological equivalent of racing thoughts in a mixed group of BD patients and healthy controls by using a bistable perception paradigm. Method Eighty-three included participants formed three groups based on participants' levels of racing thoughts reported via the Racing and Crowded Thoughts Questionnaire. Participants reported reversals in their perception during viewing of the bistable Necker cube either spontaneously, while asked to focus on one interpretation of the cube, or while asked to accelerate perceptual reversals. The dynamics of perceptual alternations were studied both at a conscious level (with manual temporal windows reflecting perceptual reversals) and at a more automatic level (with ocular temporal windows derived from ocular fixations). Results The rate of windows was less modulated by attentional conditions in participants with racing thoughts, and most clearly so for ocular windows. The rate of ocular windows was especially high when participants with racing thoughts were asked to focus on one interpretation of the Necker cube and when they received these instructions for the first time. Conclusions Our results indicate that in subjects with racing thoughts automatic perceptual processes escape cognitive control mechanisms. Racing thoughts may involve not only conscious thought mechanisms but also more automatic processes.

Languages and the Necker Cube

Over the past twenty or so years, comparative studies have revealed that important qualities of human languages are also present in the communication systems of other species.

A wrinkle in and of time: Contraction of felt duration with a single perceptual switch

The way we represent and perceive time has crucial implications for studying temporality in conscious experience. Contrasting positions posit that temporal information is separately abstracted out like any other perceptual property through specialized mechanisms or that time is represented through the temporality of experiences themselves. To add to this debate, we investigate alterations in felt time in conditions where only conscious visual experience is altered through perceptual switches while a bistable figure remains physically unchanged. We predicted that if perceived time is a function of temporally evolving conscious content, then a break in it (here via a perceptual switch) would also lead to a break in felt time. In three experiments, we showed participants a Necker cube which was manipulated to induce a perceptual switch (experiment 1(a) and 1(b)) or left to switch on its own (experiment 2). We asked participants to report both perceptual switches and felt durations (experiment 1(a) and 2) or only estimate time (experiment 1(b). Over these three experiments, we find evidence of contraction of felt time in trials with a perceptual switch, consistent with the idea that perceived time is a function of temporally evolving conscious experience. Additionally, we present a phenomenological demonstration to support our empirical data. Overall, the study provides evidence for temporal mirroring and isomorphism in visual experience, arguing for a link between the timing of experience and time perception.

How We See the World in Depth

This chapter explains how 3D vision and figure-ground perception occur in our brains. It shows how the 2D boundary and surface processes that are described in earlier chapters naturally generalize to 3D via both the FACADE (Form-And-Color-And-DEpth) theory of 3D vision and figure-ground perception, and the 3D LAMINART model that generalizes the laminar cortical circuits of Chapter 10 to 3D and naturally embodies and generalizes FACADE. Contrast-specific binocular fusion and contrast-invariant boundary formation are explained in terms of identified cells in specific layers of cortical areas V1 and V2. The correspondence problem is solved using a disparity filter that eliminates false binocular matches in layer 2/3 of V2, while it chooses the 3D binocular boundary grouping that is best supported by scenic cues. The critical role of monocular boundary information in figure-ground perception is explained and used to simulate DaVinci stereopsis percepts, along with surface-to-boundary surface contour signals and a fixation plane bias due to life-long experiences with fixated scenic features. Simulated data include the Venetian blind effect, Panum’s limiting case, dichoptic masking, 3D Craik-O’Brien-Cornsweet effect, Julesz random dot stereograms, 3D percepts of 2D pictures of shaded ellipses and discrete textures, simultaneous fusion and rivalry percepts when viewing Kulikowski and Kaufman stereograms, stimulus rivalry and eye rivalry, and bistable percepts of slanted surfaces, including the Necker cube. The size-disparity correlation enables signals from multiple scales to cooperate and compete to generate boundary representations at multiple depths. 3D percepts of natural scenes from stereograms are also simulated with these circuits.

Multistable Perception in Older Adults: Constructing a Whole from Fragments

Visual perception is constructive in nature; that is, a coherent whole is generated from ambiguous fragments that are encountered in dynamic visual scenes. Creating this coherent whole from fragmented sensory inputs requires one to detect, identify, distinguish and organize sensory input. The organization of fragments into a coherent whole is facilitated by the continuous interactions between lower level sensory inputs and higher order processes. However, age-related declines are found in both neural structures and cognitive processes (e.g., attention and inhibition). The impact of these declines on the constructive nature of visual processing was the focus of this study. Here we asked younger adults, young-old (65–79 years), and old-old adults (80+ years) to view a multistable figure (i.e., Necker cube) under four conditions (free, priming, volition, and adaptation) and report, via a button press, when percepts spontaneously changed. The oldest-olds, unlike young-olds and younger adults, were influenced by priming, had less visual stability during volition and showed less ability to adapt to multistable stimuli. These results suggest that the ability to construct a coherent whole from fragments declines with age. More specifically, vision is constructed differently in the old-olds, which might influence environmental interpretations and navigational abilities in this age group.

Multistable Perception in Older Adults: Constructing a Whole from Fragments

Visual perception is constructive in nature; that is, a coherent whole is generated from ambiguous fragments that are encountered in dynamic visual scenes. Creating this coherent whole from fragmented sensory inputs requires one to detect, identify, distinguish and organize sensory input. The organization of fragments into a coherent whole is facilitated by the continuous interactions between lower level sensory inputs and higher order processes. However, age-related declines are found in both neural structures and cognitive processes (e.g., attention and inhibition). The impact of these declines on the constructive nature of visual processing was the focus of this study. Here we asked younger adults, young-old (65–79 years), and old-old adults (80+ years) to view a multistable figure (i.e., Necker cube) under four conditions (free, priming, volition, and adaptation) and report, via a button press, when percepts spontaneously changed. The oldest-olds, unlike young-olds and younger adults, were influenced by priming, had less visual stability during volition and showed less ability to adapt to multistable stimuli. These results suggest that the ability to construct a coherent whole from fragments declines with age. More specifically, vision is constructed differently in the old-olds, which might influence environmental interpretations and navigational abilities in this age group.

Divergent Thinking Influences the Perception of Ambiguous Visual Illusions

This study investigated the relationships between personality and creativity in the perception of two different ambiguous visual illusions. Previous research has suggested that Industriousness and Openness/Intellect (as measured by the Big Five Aspects Scale) are both associated with individual differences in perceptual switching rates for binocular rivalry stimuli. Here, we examined whether these relationships generalise to the Necker Cube and the Spinning Dancer illusions. In the experimental phase of this study, participants viewed these ambiguous figures under both static and dynamic, as well as free-view and fixation, conditions. As predicted, perceptual switching rates were higher: (a) for the static Necker Cube than the Spinning Dancer, and (b) in free-view compared with fixation conditions. In the second phase of the study, personality type and divergent thinking were measured using the Big Five Aspects Scale and the Alternate Uses Task, respectively. Higher creativity/divergent thinking (as measured by the Alternate Uses Task) was found to predict greater switching rates for the static Necker Cube (but not the Spinning Dancer) under both free-view and fixation conditions. These findings suggest that there are differences in the perceptual processing of creative individuals.

Attentional Bias for the Left Visual Field in Ambiguous Necker Cube Processing

There is a view that people better react to the stimuli presented in their left visual field (LVF) due to the right lateralization of the ventral attentional network (VAN). Previous studies used color-deviant stimuli and reported LVF bias for a bottom-up attentional component. Here we examined this effect for ambiguous stimuli, Necker cubes whose processing requires bottom-up and top-down attention. We instructed subjects to report cube’s orientation, left or right, while manipulated their ambiguity. In line with other works, we suggested that ambiguity enhanced reliance on the top-down mechanisms. For low ambiguity, subjects responded faster to the left-oriented cubes. EEG power increased in the right temporoparietal junction (TPJ) for 0.3 s post-stimulus onset. For high ambiguity, we found no difference in response time and EEG power. These results may evidence VAN activation when processing the bottom-up stimulus features. The eye-tracking confirmed that subjects focused on the center of the stimulus. We hypothesized that they used peripheral vision to acquire sensory information. Therefore, the LVF attentional bias might influence the evidence accumulation process. Our results support the bottom-up attentional bias to the left visual field and provide evidence for the vital role of right TPJ in controlling bottom-up attention.