Visual perception and camouflage response to 3-D backgrounds and cast shadows in the European cuttlefish Sepia officinalis

To conceal themselves on the seafloor European cuttlefish Sepia officinalis express a large repertoire of body patterns. Scenes with 3-D relief are especially challenging because neither is it possible to directly recover visual depth from the 2-D retinal image, nor for the cuttlefish to alter its body shape to resemble nearby objects. Here we characterise cuttlefish's camouflage responses to 3-D relief, and to cast shadows, which are complementary depth cues. Animals were recorded in the presence of cylindrical objects of fixed (15mm) diameter, but varying in height, greyscale and strength of cast shadows, and to corresponding 2-D pictorial images. With the cylinders the cuttlefish expressed a ‘3-D’ body pattern, which is distinct from previously described Uniform, Mottle, and Disruptive camouflage patterns. This pattern was insensitive to variation in object height, contrast, and cast shadow, except when shadows were most pronounced, in which case the body patterns resembled those used on the 2-D backgrounds. This suggests that stationary cast shadows are not used as visual depth cues by cuttlefish, and that rather than directly matching the 2-D retinal image, the camouflage response is a two-stage process whereby the animal first classifies the physical environment and then selects an appropriate pattern. Each type of pattern is triggered by specific cues that may compete allowing the animal to select the most suitable camouflage, so the camouflage response is categorical rather than continuously variable. These findings give unique insight into how an invertebrate senses its visual environment to generate the body pattern response.

The myth of visual depth cues V: Motion parallax

Motion parallax is conventionally described as a “depth cue.” Rogers & Graham (1979) are credited with providing fairly convincing evidence for this view. Here, I argue that, just as in the case of the other so-called “depth cues,” the claim that “motion parallax” constitutes an independent factor supporting shape and depth perception is circular. Authors offering apparent demonstrations of this cue fail to properly distinguish between proximal and distal stimulus and overlook the fundamental confound of figural organization.

The myth of visual depth cues IV: Cue integration

“Visual depth cues” are conventionally invoked to explain the perception of a 3D world. They are also said to be “combined” or “integrated” for even greater effectiveness. The logical and empirical problems (Maniatis 2021a-c) that apply to the various depth cues individually and the depth cue concept generally apply to “cue integration” as well. Evidence in favor of the view is ad hoc, “models” fundamentally incomplete and contradictions never resolved.

The myth of visual depth cues IV: Shape-from-shading

The popular idea that “shading” is a shape and depth “cue” is the result of a failure to appreciate that neither shading as a physical fact nor shading as a perceptual fact can serve to explain the process leading to visual experience, because the description “shading” does not apply to the proximal stimulation, where this process begins. Both perceived shape and perceived illumination are products of figural constraints.

THE SENSE OF ENTRANCE TO A PLACE IN KASHAN HISTORICAL HOUSES

The sense of place is like a mental perception of people individuals and the conscious feeling of the environment and the entrance as important signs cause the formation of mental image and the continuity of sense of belonging to the place in people. The character that the entrance takes is an important factor for the connection between inside and outside the building. The research question is what are the criteria for recognizing entrance architecture? And how have these criteria been able to improve the continuity of the sense of belonging to the place in the inhabitants of the historical context of Kashan? In the architecture of Kashan’s houses, entrance space as a conceptual element has high importance and reflects the architectural, cultural, and social values. This important element, which is based on behavioral patterns, has lost its identity today and has been reduced scale to a separating outside from inside. Studies show that integration and integrity, the radius of vision, and visual depth are three important indices designed based on them. This research through case study and using Depth map software has examined these characteristics at the entrance of nine historical houses in Kashan. The results show that the design of these entrances has the highest degree of coherence and a maximum radius of view and due to high visual depth have high privacy.

The myth of visual “depth cues” III. “Occlusion/Interposition

Occlusion” or “interposition” are typically described as “visual depth cues.” This is not a rational claim.

The myth of visual depth cues II: Linear perspective

“Linear perspective,” used to refer to converging lines in an image, is conventionally deemed a “visual depth cue.” Perceptual evidence is not consistent with this view.

The myth of visual “depth cues” II. “Occlusion”

It is standard textbook practice to refer to “occlusion” as one of the so-called a depth-cues. However, perceived occluding relationships are a consequence of the perceptual organization of the retinal point stimulation – which contains no occluded surfaces. The perception of “occlusion” always involves amodal completion of areas perceived as partially occluded. Shapes, occlusions, and relative depth relationships are all descriptions of the percept. To treat one aspect of this percept as prior to other aspects is a logical fallacy linked to a failure to distinguish between the percept and the real world, and to a preference for adopting simple, pseudo-explanations of perceptual phenomena instead of tackling the difficult problems entailed in explaining perceptual organization.

The myth of visual “depth cues” I: “Height in the visual field”

The idea that our visual system forms a representation of the 3D world by employing various “depth cues” is well-established in mainstream vision science (e.g. Brenner & Smeets, 2018). The idea does not hold up to critical scrutiny. Here, I discuss why the idea that the height of a perceived unit in the visual field is a “cue”to its relative distance from the viewer is both unreliable and circular.

The effect of active hand movement on visually perceived depth direction

This study investigated the effect of active hand movement on the perception of 3-D depth change. In Experiment 1, the 3-D height of an object synchronously changed with the participant’s hand movement, but the 3-D height of the object was incongruent with the distance moved by the hand. The results showed no effect of active hand movement on perceived depth. This was inconsistent with the results of a previous study conducted in a similar setting with passive hand movement. It was speculated that this contradiction appeared because the conflict between the distance moved by the hand and visual depth changes were more easily detected in the active movement situation. Therefore, it was assumed that in a condition where this conflict was hard to detect, active hand movement might affect visual depth perception. To examine this hypothesis, Experiment 2 examined whether information from hand movement would resolve the ambiguity in the depth direction of a shaded visual shape. In this experiment, the distance moved by the hand could (logically) accord with either of two depth directions (concave or convex). Moreover, the discrepancy in the distances between visual and haptic perception could be ambiguous because shading cues are unreliable in estimating absolute depth. The results showed that perceived depth directions were affected by the direction of active hand movement, thus supporting the hypothesis. Based on these results, simulations based on a causal inference model were performed, and it was found that these simulations could replicate the qualitative aspects of the experimental results.