Beena Khurana

The Role of Attention in Motion Extrapolation: Are Moving Objects ‘Corrected’ or Flashed Objects Attentionally Delayed?

Objects flashed in alignment with moving objects appear to lag behind [Nijhawan, 1994 Nature (London) 370 256–257], Could this ‘flash-lag’ effect be due to attentional delays in bringing flashed items to perceptual awareness [Titchener, 1908/1973 Lectures on the Elementary Psychology of Feeling and Attention first published 1908 (New York: Macmillan); reprinted 1973 (New York: Arno Press)]? We overtly manipulated attentional allocation in three experiments to address the following questions: Is the flash-lag effect affected when attention is (a) focused on a single event in the presence of multiple events, (b) distributed over multiple events, and (c) diverted from the flashed object? To address the first two questions, five rings, moving along a circular path, were presented while observers attentively tracked one or multiple rings under four conditions: the ring in which the disk was flashed was (i) known or (ii) unknown (randomly selected from the set of five); location of the flashed disk was (i) known or (ii) unknown (randomly selected from ten locations), The third question was investigated by using two moving objects in a cost – benefit cueing paradigm, An arrow cued, with 70% or 80% validity, the position of the flashed object, Observers performed two tasks: (a) reacted as quickly as possible to flash onset; (b) reported the flash-lag effect, We obtained a significant and unaltered flash-lag effect under all the attentional conditions we employed, Furthermore, though reaction times were significantly shorter for validly cued flashes, the flash-lag effect remained uninfluenced by cue validity, indicating that quicker responses to validly cued locations may be due to the shortening of post-perceptual delays in motor responses rather than the perceptual facilitation, We conclude that the computations that give rise to the flash-lag effect are independent of attentional deployment.

Space and time in perception and action

What is the instantaneous position of a moving object from the point of view of the observer? How does a tennis player know when and where to place the racket in order to return a 120 mph serve? Does time stop sometimes and go faster at others? Space, time, and motion have played a fundamental role in extending the foundations of nineteenthand twentieth-century physics. Key breakthroughs resulted from scientists who focused not just on measurements based on rulers and clocks, but also on the role of the observer. Research targeted on the observer’s capabilities and limitations raises a promising new approach that is likely to forward our understanding of neuroscience and psychophysics. Space and Time in Perception and Action brings together theory and empirical findings from world-class experts and is written for advanced students and neuroscientists with a particular interest in the psychophysics of space, time, and motion.

Not to be and then to be : Visual representation of ignored unfamiliar faces

Negative priming, the increase in response time and/or errors to targets previously encountered as distractors, is explained by inhibitory mechanisms that block the access of distractor representations to response systems. The processing of unfamiliar human faces was investigated using negative priming. Observers viewed a row of faces to decide whether 2 target faces were the same or different. Response latencies were longer when 1 or both targets had appeared as distractors on the immediately preceding trial--evidence that never-before seen faces are represented and require inhibition. Response latencies were shorter when face targets had appeared as distractors, either corrupted with high-frequency noise or contrast inverted--evidence that representations are facilitated. Finally, response latencies remained unaltered when face targets had appeared as upside-down distractors--evidence that not all distractor representations afford response priming. The visual system indeed represents ignored unfamiliar faces, but blocks these representations only if they vie with targets for the control of action.

Compensation of neural delays in visual‐motor behaviour: No evidence for shorter afferent delays for visual motion

There are significant neural transmission and processing delays within the nervous system. How then are behaviours observed both in nature and high‐speed ball games, which require temporal accuracy to within several milliseconds, possible? Until recently, most investigators attributed the observed success in interceptive behaviours to learning or prediction built into motor programs that take these delays into account. Several investigators have proposed, however, that sensory mechanisms also contribute to compensation. Sensory compensation is particularly important when moving objects are the targets of interceptive behaviour, as in this case neural delays in the visual system could lead to errors in the communication of crucial position information of the object of interest. However, given the biological significance of visual motion the visual system could have evolved neural pathways optimized for the rapid transmission of motion signals. Alternatively, the visual system could take a sample of visual motion and compensate for the delays through prediction based on the sample. This mechanism is the visual analogue of the previously proposed “internal forward model” for motor control. We conducted four experiments using the flash‐lag effect to ask if the nervous system is naturally geared to processing moving items with a speed greater than stationary flashes. Our results show that the nervous system does not process moving items more quickly than stationary flashes.

Line by line: the ERP correlates of stroke order priming in letters

The perception of written letters reflects the action sequences that produce them. Faster recognition is observed for letters presented as sequences of strokes in a temporal order consistent with letter writing, compared to an inconsistent order. During a speeded letter identification task, parietal event-related potential (ERP) components were analysed separately for each stroke-frame in action-consistent and inconsistent stimulus sequences, during both passive and active (task-engaged) viewing. Electrophysiological data provided unique insights into stroke order priming by comparing local neural organisation during early, response-independent stages with later response-dependent stages. ERPs over posterior scalp areas revealed speeded visual processing for action-consistent stroke sequences prior to, and upon, letter completion. These signatures of perceptually facilitated letter processing were present in both active and passive viewing conditions, indicating that priming was not response-contingent, but rather an inherent part of visual letter perception. Stroke order priming is discussed in terms of matching stored letter production action codes, which upon activation provide top–down facilitation for visual processing of letters.

Temporal order of strokes primes letter recognition

Does the perception of objects that are the result of human actions reflect the underlying temporal structure of the actions that gave rise to them? We tested whether the temporal order of letter strokes influences letter recognition. In three experiments, participants were asked to identify letters that temporally unfolded as an additive sequence of letter strokes, either consistent or inconsistent with common writing action. Participants were significantly faster to identify letters from consistent temporal sequences, indicating that the initial part of the sequence contained sufficient information to prime letter recognition. We suggest that letter perception reflects the temporal structure of letter production; in other words, Simon sees as Simon does.

Spontaneous Gender Categorization in Masking and Priming Studies: Key for Distinguishing Jane from John Doe but Not Madonna from Sinatra

Facial recognition is key to social interaction, however with unfamiliar faces only generic information, in the form of facial stereotypes such as gender and age is available. Therefore is generic information more prominent in unfamiliar versus familiar face processing? In order to address the question we tapped into two relatively disparate stages of face processing. At the early stages of encoding, we employed perceptual masking to reveal that only perception of unfamiliar face targets is affected by the gender of the facial masks. At the semantic end; using a priming paradigm, we found that while to-be-ignored unfamiliar faces prime lexical decisions to gender congruent stereotypic words, familiar faces do not. Our findings indicate that gender is a more salient dimension in unfamiliar relative to familiar face processing, both in early perceptual stages as well as later semantic stages of person construal.

Motion, space and mental imagery

In the imagery debate, a key question concerns the inherent spatial nature of mental images. What do we mean by spatial representation? We explore a new idea that suggests that motion is instrumental in the coding of visual space. How is the imagery debate informed by the representation of space being determined by visual motion?

Space and Time in Perception and Action: Index

What is the instantaneous position of a moving object from the point of view of the observer? How does a tennis player know when and where to place the racket in order to return a 120 mph serve? Does time stop sometimes and go faster at others? Space, time, and motion have played a fundamental role in extending the foundations of nineteenthand twentieth-century physics. Key breakthroughs resulted from scientists who focused not just on measurements based on rulers and clocks, but also on the role of the observer. Research targeted on the observer’s capabilities and limitations raises a promising new approach that is likely to forward our understanding of neuroscience and psychophysics. Space and Time in Perception and Action brings together theory and empirical findings from world-class experts and is written for advanced students and neuroscientists with a particular interest in the psychophysics of space, time, and motion.

Space and Time in Perception and Action: Frontmatter

What is the instantaneous position of a moving object from the point of view of the observer? How does a tennis player know when and where to place the racket in order to return a 120 mph serve? Does time stop sometimes and go faster at others? Space, time, and motion have played a fundamental role in extending the foundations of nineteenthand twentieth-century physics. Key breakthroughs resulted from scientists who focused not just on measurements based on rulers and clocks, but also on the role of the observer. Research targeted on the observer’s capabilities and limitations raises a promising new approach that is likely to forward our understanding of neuroscience and psychophysics. Space and Time in Perception and Action brings together theory and empirical findings from world-class experts and is written for advanced students and neuroscientists with a particular interest in the psychophysics of space, time, and motion.