Threat modulates perception of looming visual stimuli

SummaryAmong the most critical of visual functions is the detection of potentially hazardous or threatening aspects of the environment. For example, objects on a collision course with an observer must be quickly identified to allow sufficient time to prepare appropriate defensive or avoidant responses. Directly approaching objects produce a specific accelerating pattern of optical expansion, known as ‘looming, which in theory exactly specifies time-to-collision independent of object size or distance. Such looming stimuli have been shown to trigger stereotyped defensive responses in both monkeys [1] and human infants [2]. Psychophysical results in adult participants have similarly suggested sensitivity to looming at early stages of visual processing [3]. Such findings indicate specialization of the visual system to detect and react to such ‘looming’ stimuli, and have contributed to the traditional view of looming as a purely optical cue to imminent collision [1]. Here, we investigated whether the semantic content of a looming visual stimulus affects perceived time-to-collision by manipulating its threat value. We show that time-to-collision is underestimated for threatening (snakes and spiders) compared to non-threatening (butterflies and rabbits) stimuli. Further, the magnitude of this effect is correlated with self-reported fear. Our results demonstrate affective modulation of the perception of looming stimuli, and suggest that emotion shapes basic aspects of visual perception

On the nature of near space: effects of tool use and the transition to far space

Many researchers have proposed that the near space immediately surrounding the body is represented differently than more distant space. Indeed, it has often been suggested that near space encompasses that within arm's reach. The present study used a line bisection task in healthy adults to investigate the effects of tool use on space perception, and the nature of the transition between near and far space. Subjects bisected lines at four distances controlled for both veridical and angular size using a laser pointer and a set of sticks. When the laser pointer was used, a left to right shift in bias was observed as stimuli were moved from near to far space. When a tool was used, however, a leftward bias was observed at all distances, similar to that observed with the laser pointer in near space. These results suggest that the tool expanded the range of near space. Additionally, the transition from near to far space was gradual, with no abrupt shift at arm's length (or at any other distance). In contrast to theories describing near space as that within arm's reach, these findings suggest that the representation of near space is less rigid, extending with tool use and gradually transitioning into far space

Spatial attention and the mental number line: evidence for characteristic biases and compression

Numbers are often proposed to be represented spatially as lying along a mental number line. The present study examined whether the direction of spatial attention operates similarly in physical and numerical space. Participants bisected physical lines by indicating the perceived center and “bisected” the mental number line by estimating (without calculating) the number midway between two others. Healthy participants generally show a slight leftward bias (pseudoneglect) when bisecting physical lines. In the present study, pseudoneglect was also observed on mental number line bisection and, importantly, was greater for participants who showed stronger pseudoneglect on physical line bisection. This finding suggests that hemispheric asymmetries in spatial attention operate similarly in physical and numerical space. Furthermore, this bias increased with the average of the numbers, consistent with the proposal that the spatial representation of the mental number line is nonlinearly compressive, with pairs of numbers lying closer together as their magnitude increases

Space perception and body morphology: extent of near space scales with arm length

Numerous studies have found that the near space immediately surrounding the body is represented differently than more distant space. In a previous study, we found a gradual shift in attentional bias (on a line bisection task) between near and far space (Longo and Lourenco in Neuropsychologia 44:977–981, 2006). The present study concerns the possibility that arm length relates systematically to the rate at which this gradual shift between near and far space occurs. Participants bisected lines using a laser pointer at eight distances (within and beyond arm’s reach), and the rate of shift was estimated by the slope of the least-squares regression line. A negative correlation was found between the slopes and arm length; participants with longer arms showed a more gradual shift in bias with increasing distance than those with shorter arms. These results suggest that, while near space cannot be considered categorically as that within arm’s reach, there is a systematic relation between the extent (“size”) of near space and arm length. Arm length may constitute an intrinsic metric for the representation of near space

Near space and its relation to claustrophobic fear

It is well established that the near space immediately surrounding the body (also known as peripersonal space) is represented differently than the space farther away. When bisecting horizontal lines, for example, neurologically-healthy adults show a slight leftward bias (known as pseudoneglect) in near space; this attentional bias, however, transitions rightward in far space. Recent research has used the rate at which this shift occurs to quantify the extent (i.e., size) of near space, showing consistent individual differences that relate to arm length. Here we examined whether the size of near space relates to individual differences in claustrophobic fear, as measured by reported anxiety of enclosed spaces and physically restrictive situations. Trait feelings of claustrophobic fear predicted the size of near space, even after accounting for the relation to arm length. Specifically, people with larger near spaces reported higher rates of claustrophobic fear than people with smaller near spaces. These results are consistent with a defensive function of near space representation and suggest that an over-projection of near space may play an important role in the etiology of claustrophobia

A Primate-inspired Autonomous Navigation Algorithm Using the Cognitive Mechanism of Mental Rotation

Though significant progress on autonomous navigation has been made, the natural world offers interesting examples of navigational techniques that are worth exploring and understanding. The cognitive mechanism of mental rotation has been revealed in numerous cognitive and neuroscientific experiments; its reason for existence and evolution, however, has yet to be thoroughly understood. It is speculated that this mechanism may assist primates in navigation. This paper explores how mental rotation can be used in navigation by developing an autonomous robotic navigation algorithm that draws inspiration from the mechanism. This algorithm was tested on a robot tasked with navigating to a specified goal location contained within the agent's initial view. The testing suggests that mental rotation can be used as an asset in navigation

ALICE addentum to the Technical Design Report of the time of flight system (TOF)

ALIC