Tsotsos Lab at VSS 2017
The Interaction of Target-Distractor Similarity and Visual Search Efficiency for Basic Features
Authors: Calden Wloka, Sang-Ah Yoo, Rakesh Sengupta, and John K. Tsotsos
Abstract: Visual search efficiency is commonly measured by the relationship between subject response time (RT) and display set size. Basic features are visual features for which a singleton target can be found efficiently (RT independent of set size), a situation commonly referred to as pop-out. However, the seminal work of Duncan and Humphreys (1989) demonstrated that visual search RT is also correlated with the degree of target-distractor similarity. As similarity of the target with its surrounding distractors increases (and thus the target becomes more difficult to distinguish) RT can dramatically increase. Wolfe (1998a) identified this category as hard feature search, but left both an in-depth analysis of the transition from standard feature search to a hard search as well as the efficiency of hard search largely unexplored beyond a small number of orientation trials. As far as we are aware, the interaction of these two independent factors remains relatively unstudied. For colour and size, two basic features identified by Wolfe (1998b), we systematically vary target-distractor similarity and set size to develop a well-characterized psychometric function across both dimensions. This allows us to explore if there is a transition from efficient to inefficient search, or if even hard feature searches are still efficient when performed over a basic feature difference.
Authors: Sang-Ah Yoo, John K. Tsotsos, Mazyar Fallah
Abstract: When we attend to a certain visual feature, such as a specific orientation (Tombu & Tsotsos, 2008) or specific colour (Störmer & Alvarez, 2014), processing of features nearby in that space are suppressed (i.e., feature-based surround suppression). In the present study, we investigated feature-based surround suppression in a new feature domain, motion direction, using motion repulsion as a measurement. Chen and colleagues (2005) suggested that attention to one motion direction reduces motion repulsion by inhibiting the other direction. Based on this finding, we conducted a similar direction judgment task having naïve participants. They reported perceived directions of two superimposed motions after viewing the motions for 2 sec. The directional differences between two motions systematically varied (10~70 deg) and the surfaces were separated by different colours (green or red). In the unattended condition, participants performed direction judgment tasks only, attending equally to both motions. In the attended condition, a colour cue was presented, indicating which motion participants should attend. Participants were asked to detect a brief directional shift of the cued motion and then, report the perceived motion directions. We compared the magnitude of motion repulsion between the two attention conditions. In contrast to the findings of Chen and colleagues, participants showed greater motion repulsion in the attended condition than in the unattended condition, especially when two motions moved along nearby directions. The results suggest that feature-based surround suppression exists in the motion domain and that it may occur on an early stage of motion processing where the global direction of motion is computed.
Attentional blink as a product of attentional control signals: A computational investigation
Authors: Rakesh Sengupta, Omar Abid, Asheer Bachoo, John K. Tsotsos
Abstract: Although there are several different hypotheses regarding the origin of attentional blink, including interference, inhibition, and attentional capacity based explanations, largely, there have been few attempts to cohesively understand attentional blink from a single unified visual-attentive processing model. In the current work we have chosen Cognitive Programs model of visual processing (Tsotsos et al, 2014) in order to illustrate how attentional blink arises from executive control signals of visual-attentive module and visual working memory module. We have computationally simulated the rapid serial visual presentation (RSVP) tasks detailed in Raymond et al. (1992) using letters and oriented bars in order to capture important features of attentional blink. The novel aspect of our work is that in our work attentional blink arises as a by-product of visual processing and attentive control other than less parsimonious accounts of attentional blink.