Biomedical subjects

Lavanya Reddy

Publications and source records attributed to Lavanya Reddy.

3 recordsLinked to original sources

PubMed2006

Face identification in the near-absence of focal attention.

In contrast to artificial geometric shapes, natural scenes and face-gender can be processed even when spatial attention is not fully available. In this study, we investigate whether a finer discrimination, at the level of the individual, is possible in the near-absence of focal attention. Using the paradigm, subjects performed face identification on faces of celebrities and relatively unfamiliar individuals, along with a task that is known to engage spatial attention. We find that face-identification performance is only modestly impaired under dual-task conditions. These results suggest that the visual system is well able to make complex judgments of natural stimuli, even when attention is not fully available.

Adult↗

PubMed2005

Binding is a local problem for natural objects and scenes.

Current theories hold that attention is necessary for binding the features of a visual object into a coherent representation, implying that interference should be observed when two objects must be recognized simultaneously: this is the well-known binding problem. Recent studies have suggested, however, that discriminating isolated natural scenes, objects or faces might be possible in the near absence of attention. It is still unclear what mechanisms underlie this remarkable ability. Here, we investigate whether the binding problem affects natural objects in the same way as other stimuli: is interference observed when two natural objects or scenes must be simultaneously processed? We show that in the presence of competing objects, performance in the near absence of attention depends on the relative distance between stimuli: discrimination is good for stimuli far enough apart, and poor for close enough stimuli. In contrast, seemingly simpler but unfamiliar synthetic objects could not be bound in the near absence of attention, independent of the distance between them. Thus, natural objects are special in that they suffer from the binding problem, but only locally. We surmise that this particular type of local binding for natural objects and scenes could be "hardwired" by dedicated neuronal populations.

Adult↗

PubMedDate not supplied

Visual search and dual tasks reveal two distinct attentional resources.

Most theories of visual processing assume that a target will "pop out" from an array of distractors ("parallel" visual search, e.g., color or orientation discrimination) if targets and distractors can be discriminated without attention. When the discrimination requires attention (e.g., rotated L vs. T or red-green vs. green-red bisected disks), "serial" examination is needed in visual search. Attentional requirements are also frequently assessed by measuring interference from a concurrently performed attentionally demanding task. It is commonly believed that attention acts equivalently in dual-task and visual search paradigms, based on the implicit assumption that visual attentional requirements can be defined along a single dimension. Here we show that there is no such equivalence: We report on targets that do not trigger pop-out, even though they can be discriminated from distractors with attention occupied elsewhere (natural scenes, color-orientation conjunctions); conversely, we show that certain targets that pop out among distractors need undivided attention to be effectively discriminated from distractors when presented in isolation (rotated L vs. +, depth-rotated cubes). In other words, visual search and dual-task performance reveal attentional resources along two independent dimensions. We suggest an interpretation of these results in terms of neuronal selectivities and receptive field size effects.

Attention↗