Memory effects of visual and olfactory landmark information in human wayfinding.

Non-human animals are exceptionally good at using smell to find their way through the environment. However, the use of olfactory cues for human navigation is often underestimated. Although the sense of smell is well-known for its distinct connection to memory and emotion, memory effects in human navigation using olfactory landmarks have not been studied yet. Therefore, this article compares wayfinding and recognition performance for visual and olfactory landmarks learned by 52 participants in a virtual maze. Furthermore, it is one of the first empirical studies investigating differences in memory effects on human navigation by using two separate test situations 1 month apart. The experimental task was to find the way through a maze-like virtual environment with either olfactory or visual cues at the intersections that served as decision points. Our descriptive results show that performance was above chance level for both conditions (visual and olfactory landmarks). Wayfinding performance did not decrease 1 month later when using olfactory landmarks. In contrast, when using visual landmarks wayfinding performance decreased significantly, while visual landmarks overall lead to better recognition than olfactory landmarks at both times of testing. The results demonstrate the unique character of human odor memory and support the conclusion that olfactory cues may be used in human spatial orientation. Furthermore, the present study expands the research field of human wayfinding by providing a study that investigates memory for landmark knowledge and route decisions for the visual and olfactory modality. However, more studies are required to put this important research strand forward.

Factors underlying visual illusions are illusion-specific but not feature-specific.

Common factors are ubiquitous. For example, there is a common factor, g, for intelligence. In vision, there is much weaker evidence for such common factors. For example, visual illusion magnitudes correlate only weakly with each other. Here, we investigated whether illusions are hyper-specific as in perceptual learning. First, we tested 19 variants of the Ebbinghaus illusion that differed in color, shape, or texture. Correlations between the illusion magnitudes of the different variants were mostly significant. Second, we reanalyzed a dataset from a previous experiment where 10 illusions were tested under four conditions of luminance and found significant correlations between the different luminance conditions of each illusion. However, there were only very weak correlations between the 10 different illusions. Third, five visual illusions were tested with four orientations. Again, there were significant correlations between the four orientations of each illusion, but not across different illusions. The weak inter-illusion correlations suggest that there is no unique common mechanism for the tested illusions. We suggest that most illusions make up their own factor.

TMS applied to V1 can facilitate reasoning.

Visual mental imagery is the subjective experience of seeing objects or events in front of the 'inner eye', although they are not actually present. Previous research indicates that (1) visual images help to remember what has been experienced in the past or when objects need to be inspected or manipulated, and (2) visual images are correlated with neural activity in early visual cortices, demonstrating a possible overlap between visual imagery and visual perception. However, recent research revealed that visual imagery can also disrupt cognitive processes and impede thinking. In this transcranial magnetic stimulation (TMS) experiment, participants had to solve relational reasoning problems that varied in their imageability (easy or difficult to visualize as a mental image). While solving the problems, eight 10 Hz pulses were either applied to primary visual cortex (V1) or a control site (Vertex). Our findings suggest a causal link between mental imagery, primary visual cortex, and reasoning with visual problems. Moreover, participants exhibited much lower error rates when TMS was applied to V1. We conclude that the disruption of visual images in primary visual cortex can facilitate reasoning.

Turn left where you felt unhappy: how affect influences landmark-based wayfinding.

The present work investigated the impact of affect in landmark-based wayfinding. We assumed that affect-laden landmarks improve wayfinding performance and have an impact on later landmark recognition. To investigate our hypotheses, we ran two experiments in a virtual maze. In Experiment 1, we investigated how affect-laden landmarks influence wayfinding and recognition in comparison with neutral landmarks. The aim of Experiment 2 was to focus on the affective valence of a landmark. The memory tasks of both experiments were repeated after 1 week in order to assess memory consolidation. Results showed that the best wayfinding and recognition performance occurs when negatively laden landmarks were used. In comparison with neutral and positively laden landmarks, recognition performance hardly decreased over time for the negatively laden landmarks. Our results not only support findings in the field of emotion research but also expand the concept of semantic landmark salience with respect to emotional responses.

Visual Illusions Based on Processes: New Classification System Needed.

Illusions have mainly been classified according to their phenomenological appearance. Here, I plead for a new classification approach based on processing areas or mechanisms. Classifying visual illusions according to processing areas or mechanisms may not only be valuable for a better understanding of the visual system but also for diagnostics of impairments, degenerative effects, and lesions (from retina to striate and extra-striate cortex).

Belief revision and way-finding.

Belief revision is required when veridical information surfaces that contradicts what was previously thought to be the case. In way-finding, belief revision frequently occurs, for example, when the travelled route has led one astray, instead of to one's chosen destination. In past cognitive research, the topics of belief revision and way-finding have been treated in isolation. Here, we introduce an approach for linking the two fields and assess belief revision as it occurs in the process of way-finding. We report the results of two experiments that put participants in (virtual) situations where elements of a previously learned route description do not match the actual environment (thereby requiring the revision of a previously held belief). Experiment 1 puts participants in a highly artificial virtual environment where the landmarks to be used in navigation have a low degree of semantic salience (houses of various color). Experiment 2 puts subjects in a photorealistic environment where the objects to be used in navigation are well-known landmarks (such as the Eiffel Tower) and thus have a high degree of semantic salience. In both experiments, participants are confronted with T-junctions, where a landmark that was expected to indicate the correct route is discovered to be in an unexpected location. The results of the experiments show that a participant's choice of route, in such cases, is affected by differences in the structure of the relevant initial instruction. More precisely, the route chosen by participants is affected by whether the relevant landmark was described as being on the same side of the path as they were instructed to turn (congruent case) or as located on the opposite side of the path as they were instructed to turn (incongruent case).

Implicit versus explicit processing of visual, olfactory, and multimodal landmark information in human wayfinding.

Despite the predominant focus on visual perception in most studies, the role of humans' sense of smell in navigation has often been neglected. Recent research, however, could show that humans are indeed able to use their sense of smell for orientation, particularly when processed implicitly. In this study, we investigate whether implicit perception of olfactory landmarks enhanced wayfinding performance compared to explicit perception. Fifty-two people completed a wayfinding and a recognition task in a virtual maze at two times of testing 1 month apart. Participants either received olfactory, visual, or both cues at the intersections. Wayfinding performance was better for olfactory landmarks, which were not correctly remembered in the recognition task. In contrast, wayfinding performance was better when visual landmarks were correctly remembered. In the multimodal condition, wayfinding performance was better with landmarks being remembered at t1 and remained the same at t2. Our results suggest distinct implicit processing mechanisms within the olfactory system and therefore hold important implications for the nature of spatial odor processing extending beyond explicit odor localization tasks. The study highlights the importance for future studies to develop and employ further experimental methods that capture implicit processing across all of our senses. This is crucial for a comprehensive understanding of consciousness, as olfaction strongly influences our behavior, but remains largely latent unless deliberately honed through practice.

Modality Switching in Landmark-Based Wayfinding.

This study investigates switching costs in landmark-based wayfinding using olfactory and visual landmark information. It has already been demonstrated that there seem to be no switching costs, in terms of correct route decisions, when switching between acoustically and visually presented landmarks. Olfaction, on the other hand, is not extensively focused on in landmark-based wayfinding thus far, especially with respect to modality switching. The goal of this work is to empirically test and compare visual and olfactory landmark information with regard to their suitability for wayfinding including a modality switch. To investigate this, an experiment within a virtual environment was conducted in which participants were walked along a virtual route of 12 intersections. At each intersection, landmark information together with directional information was presented, which was to be memorized and recalled in the following phase, either in the same or in the other modality (i.e., visual or olfactory). The results of the study show that, in contrast to the no-switching costs between auditory and visual landmarks in previous studies, switching costs occur when switching modality from visual to olfactory and vice versa. This is indicated by both longer decision times and fewer correct decisions. This means that a modality switch involving olfactory landmark information is possible but could lead to poorer performance. Therefore, olfaction may still be valuable for landmark-based-wayfinding. We argue that the poorer performance in the switching-condition is possibly due to higher cognitive load and the separate initial processing of odors and images in different cognitive systems.

The Giessen virtual environment laboratory: human wayfinding and landmark salience.

In our virtual environment laboratory, we focus on different topics in human spatial cognition with projects on landmark salience, route knowledge, and survey knowledge. Within this laboratory note, we provide an overview of previous, current, and future work with our virtual environment SQUARELAND.

Odors Can Serve as Landmarks in Human Wayfinding.

Scientists have shown that many non-human animals such as ants, dogs, or rats are very good at using smells to find their way through their environments. But are humans also capable of navigating through their environment based on olfactory cues? There is not much research on this topic, a gap that the present research seeks to bridge. We here provide one of the first empirical studies investigating the possibility of using olfactory cues as landmarks in human wayfinding. Forty subjects participated in a piloting study to determine the olfactory material for the main experiment. Then, 24 subjects completed a wayfinding experiment with 12 odors as orientation cues. Our results are astonishing: Participants were rather good at what we call "odor-based wayfinding." This indicates that the ability of humans to use olfactory cues for navigation is often underestimated. We discuss two different cognitive explanations and rule out the idea that our results are just an instance of sequential learning. Rather, we argue that humans can enrich their cognitive map of the environment with olfactory landmarks and may use them for wayfinding.

A rat in the sewer: How mental imagery interacts with object recognition.

The role of mental imagery has been puzzling researchers for more than two millennia. Both positive and negative effects of mental imagery on information processing have been discussed. The aim of this work was to examine how mental imagery affects object recognition and associative learning. Based on different perceptual and cognitive accounts we tested our imagery-induced interaction hypothesis in a series of two experiments. According to that, mental imagery could lead to (1) a superior performance in object recognition and associative learning if these objects are imagery-congruent (semantically) and to (2) an inferior performance if these objects are imagery-incongruent. In the first experiment, we used a static environment and tested associative learning. In the second experiment, subjects encoded object information in a dynamic environment by means of a virtual sewer system. Our results demonstrate that subjects who received a role adoption task (by means of guided mental imagery) performed better when imagery-congruent objects were used and worse when imagery-incongruent objects were used. We finally discuss our findings also with respect to alternative accounts and plead for a multi-methodological approach for future research in order to solve this issue.

Geometric-optical illusions at isoluminance.

The idea of a largely segregated processing of color and form was initially supported by observations that geometric-optical illusions vanish under isoluminance. However, this finding is inconsistent with some psychophysical studies and also with physiological evidence showing that color and luminance are processed together by largely overlapping sets of neurons in the LGN, in V1, and in extrastriate areas. Here we examined the strength of nine geometric-optical illusions under isoluminance (Delboeuf, Ebbinghaus, Hering, Judd, Müller-Lyer, Poggendorff, Ponzo, Vertical, Zöllner). Subjects interactively manipulated computer-generated line drawings to counteract the illusory effect. In all cases, illusions presented under isoluminance (both for colors drawn from the cardinal L-M or S-(L+M) directions of DKL color space) were as effective as the luminance versions (both for high and low contrast). The magnitudes of the illusion effects were highly correlated across subjects for the different conditions. In two additional experiments we determined that the strong illusions observed under isoluminance were not due to individual deviations from the photometric point of isoluminance or due to chromatic aberrations. Our findings show that our conscious percept is affected similarly for both isoluminance and luminance conditions, suggesting that the joint processing for chromatic and luminance defined contours may extend well beyond early visual areas.

Uniform versus random orientation in fading and filling-in.

V1 responses to an optimally oriented test line in the receptive field center may be modulated by placing lines of same or different orientations in the surround. While iso-orientation produces strong inhibition, cross-orientation enhances the response [Knierim, J. J., & Van Essen, D. C. (1992). Neuronal responses to static texture patterns in area V1 of the alert macaque monkey. Journal of Neurophysiology, 67, 961-980]. We looked for a perceptual correlate of neuronal texture modulation using perceived salience as well as fading and filling-in as response criteria. Two patterns by Vicario (1998) [Vicario, G. B. (1998). On Wertheimer's principles of organization. In G. Stemberger, (Ed.), Gestalt theory, (Vol. 20, pp. 256-270). Vienna: Verlag Krammer] served as targets. One consisted of randomly oriented bars in the center and uniformly oriented bars in the surround, while the other had bars of uniform orientation in the center and bars of random orientation in the surround. In spite of identical texture contrast at the boundary, the first pattern was judged more salient than the second and its center took more time to fade. When the surround was decreased in width, fading time followed no systematic trend and filling-in was increasingly replaced by filling-out. A higher salience and longer fading time for stimuli with a uniformly as opposed to randomly oriented surround was also obtained when the bars in the center were replaced by dotted arrays. However, no asymmetry was found for the converse patterns when dots were in the surround and bars in the center. Findings are interpreted in terms of stronger surround suppression exerted by randomly oriented bars as compared to uniformly oriented bars. Modeling suggests that this suppression may mediate a statistical computation by the visual system, aimed at detecting a texture boundary between the center and surround when the center texture was likely generated by a different random process than that which generated the surround.

Reversal of apparent rotation in the Enigma-figure with and without motion adaptation and the effect of T-junctions.

We studied the time course of apparent rotation and directional reversal in Leviant's Enigma figure. On average, periods of clockwise rotation lasted 5.0 s as opposed to 4.4 for counter-clockwise rotation, resulting in an average reversal frequency of 6.4 within 30 s. At the beginning of a trial, clockwise rotation was perceived almost twice as often as counter-clockwise rotation. This bias could be shifted by previous adaptation to a black-and-white rotating sector disk, suggesting a neural interaction between real motion and illusory motion. We further studied Enigma-type motion on a chromatic bar superimposed onto a black-and-white linear grating. Illusory motion was strongest when the bar was oriented at 90 deg to the grating lines and became progressively weaker with a decrease in angle. This suggests that T-junctions formed by the radial rays impinging onto the colored rings of the Enigma figure are instrumental for eliciting the rotary motion and may rule out a low-level sensory origin of the illusion.

Filling-in with colour: different modes of surface completion.

We investigated the figural dynamics of filling-in processes in figures with more than one possible figure-ground organisation. Using a central disk and two concentric rings as well as similar stimuli consisting of three nested squares or parallel stripes, we tested for filling-in with different equiluminant colour combinations. We observed four modes of filling-in: First, in most of the cases, the inner ring assumed the colour of the central disk and outer ring (M1). Second, the central disk became filled-in with the colour of the inner ring, without any colour change on the outer ring (M2). Third, in a first step, the colour of the inner ring spread onto the central disk; then, in a second step, the colour of the outer ring spread over the whole stimulus (M3). This two step filling-in process has not been reported so far. Fourth, a mode (M4) was sometimes observed that was characterised by the central disk and outer ring assuming the colour of the inner ring. Thus, colour filling-in or colour spreading proceeded both in a centripetal (periphery to fovea) as well as a centrifugal direction. The colours red and yellow proved to be stronger inducers than blue and green. Conversely, the latter colours became filled-in more easily than the former. The filled-in colour was always that of the inducing stimulus, i.e., there was no colour mixture. This suggests a long-range, neural process underlying filling-in under these conditions.

Perceptual filling-in from the edge of the blind spot.

Looking at the world with one eye, we do not notice a scotoma in the receptor-free area of the visual field where the optic nerve leaves the eye. Rather we perceive the brightness, color, and texture of the adjacent area as if they were actually there. The mechanisms underlying this kind of perceptual filling-in remain controversial. To better understand these processes, we determined the minimum region around the blind spot that needs to be stimulated for filling-in by carefully mapping the blind spot and presenting individually fitted stimulus frames of different width around it. Uniform filling-in was observed with frame widths as narrow as 0.05 degrees visual angle for color and 0.2 degrees for texture. Filling-in was incomplete, when the frame was no longer contiguous with the blind spot border due to an eye movement. These results are consistent with the idea that perceptual filling-in of the blind spot depends on local processes generated at the physiological edge of the cortical representation.

Multimodal Integration of Spatial Information: The Influence of Object-Related Factors and Self-Reported Strategies.

Spatial representations are a result of multisensory information integration. More recent findings suggest that the multisensory information processing of a scene can be facilitated when paired with a semantically congruent auditory signal. This congruency effect was taken as evidence that audio-visual integration occurs for complex scenes. As navigation in our environment consists of a seamless integration of complex sceneries, a fundamental question arises: how is human landmark-based wayfinding affected by multimodality? In order to address this question, two experiments were conducted in a virtual environment. The first experiment compared wayfinding and landmark recognition performance in unimodal visual and acoustic landmarks. The second experiment focused on the congruency of multimodal landmark combinations and additionally assessed subject's self-reported strategies (i.e., whether they focused on direction sequences or landmarks). We demonstrate (1) the equality of acoustic and visual landmarks and (2) the congruency effect for the recognition of landmarks. Additionally, the results point out that self-reported strategies play a role and are an under-investigated topic in human landmark-based wayfinding.