ATTENTION AND PERCEPTION
A central question in the field of attention concerns the detection, categorization and identification of stimuli in the absence of visual attention. This issue has a long history, dating back to pioneering studies investigating the nature of attentional mechanisms, and triggering renewed interest and controversy in recent years. Our studies focus on the role of attention in processing individual stimuli and object-object or scene-object associative relations, especially when these involve stimuli that are strictly irrelevant to one's task-settings. Our findings consistently display a qualitative dissociation between prioritized (e.g., searched, relevant) and non-prioritized (e.g., non-searched, irrelevant) distractors with respect to the role of spatial attention in recognition of stimuli and their associative relations. We show that when viewing a scene at a glance, attention is typically required for stimulus and object-scene relational processing, unless one is actively searching for these stimuli and/or associations.
CONTEXT AND VISUAL MEMORY
While it is long known that contextual information affects memory for an object’s identity (e.g., its basic level category), we find that schematic knowledge additionally enhances memory for the precise visual appearance of an item. This finding may be counterintuitive since schematic knowledge is typically thought to contain information about the “gist” of a scene (i.e., its general theme and the main objects contained within it), while being abstracted of specific instances or episodic detail. We suggest that when viewing the world at a glance, i.e., under very brief exposure conditions in which multiple objects compete for limited attentional capacity, perceptual grouping factors (such as Gestalt principles) as well as ‘conceptual grouping’ factors (such as semantic, categorical, or action relations among stimuli) may assist in reducing stimulus competition and in streamlining perception. Our findings suggest that, indeed, visual context may not only facilitate memory for objects’ “gist” (i.e., at the basic-level category), but also for the specific instances (i.e., the visual details) of an event.
In a third line of research, we explore the extent to which visual and semantic properties of every-day objects interact with other cognitive systems associated with quantity and number representation. While the two types of processing are seemingly distinct and independent of each other, there are reasons to believe that stimulus properties such as an object’s distance from the self, or its real-world size, are associated with magnitude or numeral representation. Note that it is long known that physical size interacts with number perception, however, we asked whether the conceptual size of objects (i.e., the semantic knowledge of their real-world size, despite changing retinal size) additionally affects numeral value perception. Our studies show that, indeed, semantic knowledge of real-world size is tightly linked to a symbolic representation of magnitude i.e., number value. Furthermore, using neuroimaging techniques, we show that regions within the ventral visual cortex which are known to be responsive to the real-world size of every-day objects are also sensitive to a more abstract, symbolic representation of size.
PSYCHOPHYSIOLOGICAL DETECTION OF CONCEALED KNOWLEDGE
I have long been interested in the psychophysiological detection of concealed knowledge. In a series of studies, we have examined the use of behavioral and physiological measures in knowledge detection, when administrating the Concealed Information Test (CIT). We have also examined the role of retroactive interference as a potential countermeasure which may weaken memory traces of the concealed items and attenuate the physiological responses elicited by them. Our results reveal that both memory for the concealed details and the physiological responsiveness to these details are attenuated under the memory-interference conditions (relative to a control group), suggesting that learning hypothetical crime details just before taking the CIT may serve as an effective countermeasure by guilty suspects.