A shark's eye view: testing the ‘mistaken identity theory’ behind shark bites on humans

2021 ◽  
Vol 18 (183) ◽  
Author(s):  
Laura A. Ryan ◽  
David J. Slip ◽  
Lucille Chapuis ◽  
Shaun P. Collin ◽  
Enrico Gennari ◽  
...  
Keyword(s):  
Visual Motion ◽  
Identity Theory ◽  
White Shark ◽  
Public Concern ◽  
Motion Cues ◽  
Video Footage ◽  
Mistaken Identity ◽  
The Difference ◽  
Typical Prey

Shark bites on humans are rare but are sufficiently frequent to generate substantial public concern, which typically leads to measures to reduce their frequency. Unfortunately, we understand little about why sharks bite humans. One theory for bites occurring at the surface, e.g. on surfers, is that of mistaken identity, whereby sharks mistake humans for their typical prey (pinnipeds in the case of white sharks). This study tests the mistaken identity theory by comparing video footage of pinnipeds, humans swimming and humans paddling surfboards, from the perspective of a white shark viewing these objects from below. Videos were processed to reflect how a shark's retina would detect the visual motion and shape cues. Motion cues of humans swimming, humans paddling surfboards and pinnipeds swimming did not differ significantly. The shape of paddled surfboards and human swimmers was also similar to that of pinnipeds with their flippers abducted. The difference in shape between pinnipeds with abducted versus adducted flippers was bigger than between pinnipeds with flippers abducted and surfboards or human swimmers. From the perspective of a white shark, therefore, neither visual motion nor shape cues allow an unequivocal visual distinction between pinnipeds and humans, supporting the mistaken identity theory behind some bites.

8. Mistake

2017 ◽  
Author(s):  
Richard Taylor ◽  
Damian Taylor
Keyword(s):  
Case Law ◽  
Legal Knowledge ◽  
Face To Face ◽  
Mistaken Identity ◽  
Common Mistake ◽  
Key Points ◽  
The Difference

Without assuming prior legal knowledge, books in the Directions series introduce and guide readers through key points of law and legal debate. Questions, diagrams and exercises help readers to engage fully with each subject and check their understanding as they progress. This chapter discusses the various ways of classifying mistakes including communication mistakes, mistakes of fact, common mistake and unilateral mistake. It then looks at the case law on mistaken identity and the distinctions between face-to-face and correspondence contracts. Finally, it looks at the restrictive rules on common mistake, including the difference between fundamental mistake and mistake as to quality, and their relationship with the doctrine of frustration and the demise of the category of equitable mistake.

scholarly journals Detection of deceptive motions in rugby from visual motion cues

PLoS ONE ◽  
2019 ◽  
Vol 14 (9) ◽  
pp. e0220878 ◽  
Author(s):  
Sean Dean Lynch ◽  
Anne-Hélène Olivier ◽  
Benoit Bideau ◽  
Richard Kulpa
Keyword(s):  
Visual Motion ◽  
Motion Cues ◽  
Visual Motion Cues

scholarly journals Motion detection: cells, circuits and algorithms

Neuroforum ◽  
2018 ◽  
Vol 24 (2) ◽  
pp. A61-A72 ◽  
Author(s):  
Giordano Ramos-Traslosheros ◽  
Miriam Henning ◽  
Marion Silies
Keyword(s):  
Motion Detection ◽  
Visual Motion ◽  
Motion Cues ◽  
Detection Algorithms ◽  
Preferred Direction ◽  
Direct Measurements ◽  
Classical Models ◽  
Light Signals ◽  
Circuit Components ◽  
Visual Motion Cues

Abstract Many animals use visual motion cues to inform different behaviors. The basis for motion detection is the comparison of light signals over space and time. How a nervous system performs such spatiotemporal correlations has long been considered a paradigmatic neural computation. Here, we will first describe classical models of motion detection and introduce core motion detecting circuits in Drosophila. Direct measurements of the response properties of the first direction-selective cells in the Drosophila visual system have revealed new insights about the implementation of motion detection algorithms. Recent data suggest a combination of two mechanisms, a nonlinear enhancement of signals moving into the preferred direction, as well as a suppression of signals moving into the opposite direction. These findings as well as a functional analysis of the circuit components have shown that the microcircuits that process elementary motion are more complex than anticipated. Building on this, we have the opportunity to understand detailed properties of elementary, yet intricate microcircuits.

scholarly journals The effect of contextual cues on the encoding of motor memories

2013 ◽  
Vol 109 (10) ◽  
pp. 2632-2644 ◽  
Author(s):  
Ian S. Howard ◽  
Daniel M. Wolpert ◽  
David W. Franklin
Keyword(s):  
Visual Feedback ◽  
Visual Cues ◽  
Visual Motion ◽  
Substantial Reduction ◽  
Visual Display ◽  
Visual Object ◽  
Contextual Cues ◽  
Motion Cues ◽  
Visual Motion Cues ◽  
Display Location

Several studies have shown that sensory contextual cues can reduce the interference observed during learning of opposing force fields. However, because each study examined a small set of cues, often in a unique paradigm, the relative efficacy of different sensory contextual cues is unclear. In the present study we quantify how seven contextual cues, some investigated previously and some novel, affect the formation and recall of motor memories. Subjects made movements in a velocity-dependent curl field, with direction varying randomly from trial to trial but always associated with a unique contextual cue. Linking field direction to the cursor or background color, or to peripheral visual motion cues, did not reduce interference. In contrast, the orientation of a visual object attached to the hand cursor significantly reduced interference, albeit by a small amount. When the fields were associated with movement in different locations in the workspace, a substantial reduction in interference was observed. We tested whether this reduction in interference was due to the different locations of the visual feedback (targets and cursor) or the movements (proprioceptive). When the fields were associated only with changes in visual display location (movements always made centrally) or only with changes in the movement location (visual feedback always displayed centrally), a substantial reduction in interference was observed. These results show that although some visual cues can lead to the formation and recall of distinct representations in motor memory, changes in spatial visual and proprioceptive states of the movement are far more effective than changes in simple visual contextual cues.

scholarly journals Behavioral and neuronal underpinnings of safety in numbers in fruit flies

2019 ◽  
Author(s):  
Clara H Ferreira ◽  
Marta A Moita
Keyword(s):  
Defensive Behavior ◽  
Visual Motion ◽  
Fruit Flies ◽  
Social Cues ◽  
Freezing Behavior ◽  
Motion Cues ◽  
Safety In Numbers ◽  
Visual Motion Cues

AbstractLiving in a group allows individuals to decrease their defenses enabling other beneficial behaviors such as foraging. The detection of a threat through social cues is widely reported, however the safety cues that guide animals to break away from a defensive behavior and resume alternate activities remain elusive. Here we show that fruit flies displayed a graded decrease in freezing behavior, triggered by an inescapable threat, with increasing group sizes. Furthermore, flies used the cessation of movement of other flies as a cue of threat and its resumption as a cue of safety. Finally, we found that lobula columnar neurons, LC11, mediate the propensity for freezing flies to resume moving in response to the movement of others. By identifying visual motion cues, and the neurons involved in their processing, as the basis of a social safety cue this study brings new insights into the neuronal basis of safety in numbers.

scholarly journals Cross-Modal Cue Effects in Motion Processing

2019 ◽  
Vol 32 (1) ◽  
pp. 45-65 ◽  
Author(s):  
G. M. Hanada ◽  
J. Ahveninen ◽  
F. J. Calabro ◽  
A. Yengo-Kahn ◽  
L. M. Vaina
Keyword(s):  
Visual Motion ◽  
Detection Threshold ◽  
Relevant Information ◽  
Motion Processing ◽  
Spatial Cues ◽  
Auditory Cues ◽  
Motion Patterns ◽  
Motion Cues ◽  
The Everyday ◽  
Feature Based

Abstract The everyday environment brings to our sensory systems competing inputs from different modalities. The ability to filter these multisensory inputs in order to identify and efficiently utilize useful spatial cues is necessary to detect and process the relevant information. In the present study, we investigate how feature-based attention affects the detection of motion across sensory modalities. We were interested to determine how subjects use intramodal, cross-modal auditory, and combined audiovisual motion cues to attend to specific visual motion signals. The results showed that in most cases, both the visual and the auditory cues enhance feature-based orienting to a transparent visual motion pattern presented among distractor motion patterns. Whereas previous studies have shown cross-modal effects of spatial attention, our results demonstrate a spread of cross-modal feature-based attention cues, which have been matched for the detection threshold of the visual target. These effects were very robust in comparisons of the effects of valid vs. invalid cues, as well as in comparisons between cued and uncued valid trials. The effect of intramodal visual, cross-modal auditory, and bimodal cues also increased as a function of motion-cue salience. Our results suggest that orienting to visual motion patterns among distracters can be facilitated not only by intramodal priors, but also by feature-based cross-modal information from the auditory system.

Eye Movements in Response to Dichoptic Motion: Evidence for a Parallel-Hierarchical Structure of Visual Motion Processing in Primates

2008 ◽  
Vol 99 (5) ◽  
pp. 2329-2346 ◽  
Author(s):  
Ryusuke Hayashi ◽  
Kenichiro Miura ◽  
Hiromitsu Tabata ◽  
Kenji Kawano
Keyword(s):  
Eye Movements ◽  
Visual Motion ◽  
Large Field ◽  
Motion Processing ◽  
Motion Cues ◽  
First Order ◽  
Visual Motion Processing ◽  
Ocular Following ◽  
Winner Take All ◽  
Take All

Brief movements of a large-field visual stimulus elicit short-latency tracking eye movements termed “ocular following responses” (OFRs). To address the question of whether OFRs can be elicited by purely binocular motion signals in the absence of monocular motion cues, we measured OFRs from monkeys using dichoptic motion stimuli, the monocular inputs of which were flickering gratings in spatiotemporal quadrature, and compared them with OFRs to standard motion stimuli including monocular motion cues. Dichoptic motion did elicit OFRs, although with longer latencies and smaller amplitudes. In contrast to these findings, we observed that other types of motion stimuli categorized as non-first-order motion, which is undetectable by detectors for standard luminance-defined (first-order) motion, did not elicit OFRs, although they did evoke the sensation of motion. These results indicate that OFRs can be driven solely by cortical visual motion processing after binocular integration, which is distinct from the process incorporating non-first-order motion for elaborated motion perception. To explore the nature of dichoptic motion processing in terms of interaction with monocular motion processing, we further recorded OFRs from both humans and monkeys using our novel motion stimuli, the monocular and dichoptic motion signals of which move in opposite directions with a variable motion intensity ratio. We found that monocular and dichoptic motion signals are processed in parallel to elicit OFRs, rather than suppressing each other in a winner-take-all fashion, and the results were consistent across the species.

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