Processing spatial relations with different apertures of attention

Neuropsychological studies suggest the existence of lateralized networks that represent categorical and coordinate types of spatial information. In addition, studies with neural networks have shown that they encode more effectively categorical spatial judgments or coordinate spatial judgments, if their input is based, respectively, on units with relatively small, nonoverlapping receptive fields, as opposed to units with relatively large, overlapping receptive fields. These findings leave open the question of whether interactive processes between spatial detectors and types of spatial relations can be modulated by spatial attention. We hypothesized that spreading the attention window to encompass an area that includes two objects promotes coordinate spatial relations, based on coarse coding by large, overlapping, receptive fields. In contrast, narrowing attention to encompass an area that includes only one of the objects benefits categorical spatial relations, by effectively parsing space. By use of a cueing procedure, the spatial attention window was manipulated to select regions of differing areas. As predicted, when the attention window was large, coordinate spatial transformations were noticed faster than categorical transformations; in contrast, when the attention window was relatively smaller, categorical spatial transformations were noticed faster than coordinate transformations. Another novel finding was that coordinate changes were noticed faster when cueing an area that included both objects as well as the empty space between them than when simultaneously cueing both areas including the objects while leaving the gap between them uncued.     

Impulse processing: a dynamical systems model of incremental eye movements in the visual world paradigm

The Visual World Paradigm (VWP) presents listeners with a challenging problem: They must integrate two disparate signals, the spoken language and the visual context, in support of action (e.g., complex movements of the eyes across a scene). We present Impulse Processing, a dynamical systems approach to incremental eye movements in the visual world that suggests a framework for integrating language, vision, and action generally. Our approach assumes that impulses driven by the language and the visual context impinge minutely on a dynamical landscape of attractors corresponding to the potential eye-movement behaviors of the system. We test three unique predictions of our approach in an empirical study in the VWP, and describe an implementation in an artificial neural network. We discuss the Impulse Processing framework in relation to other models of the VWP.     

Flicker-light induced visual phenomena: frequency dependence and specificity of whole percepts and percept features

Flickering light induces visual hallucinations in human observers. Despite a long history of the phenomenon, little is known about the dependence of flicker-induced subjective impressions on the flicker frequency. We investigate this question using Ganzfeld stimulation and an experimental paradigm combining a continuous frequency scan (1–50 Hz) with a focus on re-occurring, whole percepts. On the single-subject level, we find a high degree of frequency stability of percepts. To generalize across subjects, we apply two rating systems, (1) a set of complex percept classes derived from subjects’ reports and (2) an enumeration of elementary percept features, and determine distributions of occurrences over flicker frequency. We observe a stronger frequency specificity for complex percept classes than elementary percept features. Comparing the similarity relations among percept categories to those among frequency profiles, we observe that though percepts are preferentially induced by particular frequencies, the frequency does not unambiguously determine the experienced percept.     

Are visual features of a looming or receding object processed in a capacity-free manner?

Numerous experiments have examined whether moving stimuli capture spatial attention but none have sought to determine whether visual features of looming and receding objects are extracted in a capacity-free manner. The current experiment (N = 28) used the task-choice procedure originated by Besner and Care (2003) to examine this possibility. Stimuli were presented in 3D space by manipulating retinal disparity. Results indicate that features of an object are extracted in a capacity-free manner for both looming and receding objects for participants who consciously perceive motion but not for participants who do not consciously perceive motion. These results suggest that the cognitive system is biased to process potentially animate objects, perhaps because of the evolutionary advantage this cognitive ability may provide.     

Remembering from any angle: the flexibility of visual perspective during retrieval

When recalling autobiographical memories, individuals often experience visual images associated with the event. These images can be constructed from two different perspectives: first person, in which the event is visualized from the viewpoint experienced at encoding, or third person, in which the event is visualized from an external vantage point. Using a novel technique to measure visual perspective, we examined where the external vantage point is situated in third-person images. Individuals in two studies were asked to recall either 10 or 15 events from their lives and describe the perspectives they experienced. Wide variation in spatial locations was observed within third-person perspectives, with the location of these perspectives relating to the event being recalled. Results suggest remembering from an external viewpoint may be more common than previous studies have demonstrated.     

Consciousness and modality: on the possible preserved visual consciousness in blindsight subjects

In a recent paper, Brogaard (2011) presents counter-arguments to the conclusions of an experiment with blindsight subject GR. She argues that contrary to the apparent findings that GR’s preserved visual abilities relate to degraded visual experiences, she is in fact fully unconscious of the stimuli she correctly identifies. In this paper, we present arguments and evidence why Brogaard’s argument does not succeed in its purpose. We suggest that not only is relevant empirical evidence in opposition to Brogaard’s argument, her argument misconstrues necessary criteria to decide whether a conscious experience is visual or not visual.     

The change probability effect: incidental learning, adaptability, and shared visual working memory resources

Statistical properties in the visual environment can be used to improve performance on visual working memory (VWM) tasks. The current study examined the ability to incidentally learn that a change is more likely to occur to a particular feature dimension (shape, color, or location) and use this information to improve change detection performance for that dimension (the change probability effect). Participants completed a change detection task in which one change type was more probable than others. Change probability effects were found for color and shape changes, but not location changes, and intentional strategies did not improve the effect. Furthermore, the change probability effect developed and adapted to new probability information quickly. Finally, in some conditions, an improvement in change detection performance for a probable change led to an impairment in change detection for improbable changes.     

The whole is indeed more than the sum of its parts: perceptual averaging in the absence of individual item representation

We tested Ariely's (2001) proposal that the visual system represents the overall statistical properties of sets of objects against alternative accounts of rapid averaging involving sub-sampling strategies. In four experiments, observers could rapidly extract the mean size of a set of circles presented in an RSVP sequence, but could not reliably identify individual members. Experiment 1 contrasted performance on a member identification task with performance on a mean judgment task, and showed that the tasks could be dissociated based on whether the test probe was presented before or after the sequence, suggesting that member identification and mean judgment are subserved by different mechanisms. In Experiment 2, we confirmed that when given a choice between a probe corresponding to the mean size of the set and a foil corresponding to the mean of the smallest and largest items only, the former is preferred to the latter, even when observers are explicitly instructed to average only the smallest and largest items. Experiment 3 showed that a test item corresponding to the mean size of the set could be reliably discriminated from a foil but the largest item in the set, differing by an equivalent amount, could not. In Experiment 4, observers rejected test items dissimilar to the mean size of the set in a member identification task, favoring test items that corresponded to the mean of the set over items that were actually shown. These findings suggest that mean representation is accomplished without explicitly encoding individual items.     

Visualizing the temporal dynamics of spatial information processing responsible for the Simon effect and its amplification by inhibition of return

Research has shown that the Simon effect is larger for targets suffering from inhibition of return (IOR). We used speed–accuracy trade-off (SAT) methodology to explore the temporal dynamics underlying this interaction. In Experiment 1, a new method for sorting the data was used to reveal a monotonic decay in the impact of task-irrelevant location information that is responsible for the Simon effect. In Experiment 2, we show that IOR delays both task-relevant identity and task-irrelevant location codes; a relatively longer delay for location than identity codes accounts for the effect of IOR on the Simon effect. When location information was made task-relevant in Experiment 3, IOR delayed the accumulation of this information by about the same amount as when location was irrelevant. The results suggest that IOR, therefore, has a greater effect on location than identity information.     

Walk this way: approaching bodies can influence the processing of faces

A highly familiar type of movement occurs whenever a person walks towards you. In the present study, we investigated whether this type of motion has an effect on face processing. We took a range of different 3D head models and placed them on a single, identical 3D body model. The resulting figures were animated to approach the observer. In a first series of experiments, we used a sequential matching task to investigate how the motion of an approaching person affects immediate responses to faces. We compared observers’ responses following approach sequences to their performance with figures walking backwards (receding motion) or remaining still. Observers were significantly faster in responding to a target face that followed an approach sequence, compared to both receding and static primes. In a second series of experiments, we investigated long-term effects of motion using a delayed visual search paradigm. After studying moving or static avatars, observers searched for target faces in static arrays of varying set sizes. Again, observers were faster at responding to faces that had been learned in the context of an approach sequence. Together these results suggest that the context of a moving body influences face processing, and support the hypothesis that our visual system has mechanisms that aid the encoding of behaviourally-relevant and familiar dynamic events.