Brad Wyble

The Simultaneous Type, Serial Token Model of Temporal Attention and Working Memory

A detailed description of the simultaneous type, serial token (ST2) model is presented. ST2 is a model of temporal attention and working memory that encapsulates 5 principles: (a) M. M. Chun and M. C. Potters (1995) 2-stage model, (b) a Stage 1 salience filter, (c) N. G. Kanwishers (1987, 1991) types-tokens distinction, (d) a transient attentional enhancement, and (e) a mechanism for associating types with tokens called the binding pool. The authors instantiate this theoretical position in a connectionist implementation, called neural-ST2, which they illustrate by modeling temporal attention results focused on the attentional blink (AB). They demonstrate that the ST2 model explains a spectrum of AB findings. Furthermore, they highlight a number of new temporal attention predictions arising from the ST2 theory, which are tested in a series of behavioral experiments. Finally, the authors review major AB models and theories and compare them with ST2.

The attentional blink: Past, present, and future of a blind spot in perceptual awareness

A survey of the attention literature reveals the prominence of the attentional blink (AB)--a deficit in reporting the second of two targets when presented in close temporal succession. For two decades, this robust attentional phenomenon has been a major topic in attention research because it is informative about the rate at which stimuli can be encoded into consciously accessible representations. The pace of discovery and theoretical advancement concerning the AB has increased rapidly in the past few years with emphasis on new neurophysiological evidence and computational accounts of attentional processes. In this review we extract the central questions and the main lessons learnt from the past, and subsequently provide important directions for future research.

Attentional Episodes in Visual Perception

Is ones temporal perception of the world truly as seamless as it appears? This article presents a computationally motivated theory suggesting that visual attention samples information from temporal episodes (episodic simultaneous type/serial token model; Wyble, Bowman, & Nieuwenstein, 2009). Breaks between these episodes are punctuated by periods of suppressed attention, better known as the attentional blink (Raymond, Shapiro, & Arnell, 1992). We test predictions from this model and demonstrate that participants were able to report more letters from a sequence of 4 targets presented in a dense temporal cluster than from a sequence of 4 targets interleaved with nontargets. However, this superior report accuracy comes at a cost in impaired temporal order perception. Further experiments explore the dynamics of multiple episodes and the boundary conditions that trigger episodic breaks. Finally, we contrast the importance of attentional control, limited resources, and memory capacity constructs in the model.

Contingent attentional capture by conceptually relevant images

Attentional capture is an unintentional shift of visuospatial attention to the location of a distractor that is either highly salient, or relevant to the current task set. The latter situation is referred to as contingent capture, in that the effect is contingent on a match between characteristics of the stimuli and the task-defined attentional-control settings of the viewer. Contingent capture has been demonstrated for low-level features, such as color, motion, and orientation. In the present paper we show that contingent capture can also occur for conceptual information at the superordinate level (e.g., sports equipment, marine animal, dessert food). This effect occurs rapidly (i.e., within 200 ms), is a spatial form of attention, and is contingent on attentional-control settings that change on each trial, suggesting that natural images can be decoded into their conceptual meaning to drive shifts of attention within the time course of a single fixation.

Subliminal Salience Search Illustrated: EEG Identity and Deception Detection on the Fringe of Awareness

We propose a novel deception detection system based on Rapid Serial Visual Presentation (RSVP). One motivation for the new method is to present stimuli on the fringe of awareness, such that it is more difficult for deceivers to confound the deception test using countermeasures. The proposed system is able to detect identity deception (by using the first names of participants) with a 100% hit rate (at an alpha level of 0.05). To achieve this, we extended the classic Event-Related Potential (ERP) techniques (such as peak-to-peak) by applying Randomisation, a form of Monte Carlo resampling, which we used to detect deception at an individual level. In order to make the deployment of the system simple and rapid, we utilised data from three electrodes only: Fz, Cz and Pz. We then combined data from the three electrodes using Fishers method so that each participant was assigned a single p-value, which represents the combined probability that a specific participant was being deceptive. We also present subliminal salience search as a general method to determine what participants find salient by detecting breakthrough into conscious awareness using EEG.

A reciprocal relationship between bottom-up trace strength and the attentional blink bottleneck : Relating the LC-NE and ST2 models

Abstract There is considerable current interest in neural modeling of the attentional blink phenomenon. Two prominent models of this task are the Simultaneous Type Serial Token (ST2) model and the Locus Coeruleus–Norepinephrine (LC–NE) model. The former of these generates a broad spectrum of behavioral data, while the latter provides a neurophysiologically detailed account. This paper explores the relationship between these two approaches. Specifically, we consider the spectrum of empirical phenomena that the two models generate, particularly emphasizing the need to generate a reciprocal relationship between bottom-up trace strength and the blink bottleneck. Then we discuss the implications of using ST2 token mechanisms in the LC–NE setting.

The root cause of the attentional blink: First-target processing or disruption of input control?

Identification of the second of two targets (T2) is impaired when presented shortly after the first (T1). T1-based theories ascribe this attentional blink (AB) to a T1-initiated period of inattention. Distractor-based theories ascribe it to a disruption of input control caused by post-T1 distractors. The finding that an AB occurs without intertarget distractors (Nieuwenstein, Potter, & Theeuwes, Journal of Experimental Psychology: Human Perception and Performance 35:159-169, 2009) seemingly disconfirms distractor-based theories. The present experiments addressed different ways in which distractor-based theories might account for that finding. Intertarget events were varied in four experiments. Experiment 1 replicated Nieuwenstein, Potter, and Theeuwes’s findings. The next two experiments tested two ways (lack of visual stimulation, violation of expectation) in which the blank intertarget interval might cause an AB. Experiment 4 explored whether backward-masking of T1 can account entirely for the larger AB obtained with intervening distractors or whether distractors also disrupt input control. The results disconfirm predictions from distractor-based theories and support the claim of T1-based theories that T1 processing alone is sufficient for the AB. Simulations based on the eSTST (Wyble, Bowman, & Nieuwenstein, Journal of Experimental Psychology: Human Perception and Performance 35:787-807, 2009) and the B&B models (Olivers & Meeter, Psychological Research, 115, 836-863 2008) were compared. Predictions were more accurate from the T1-based theory (eSTST) than from the distractor-based theory (B&B).

TRANSIENT ATTENTIONAL ENHANCEMENT DURING THE ATTENTIONAL BLINK: EEG CORRELATES OF THE ST 2 MODEL

The Attentional Blink (AB) is a well studied temporal attention phenomenon, and is particularly suitable for investigating the nature and limits of conscious perception. The AB employs Rapid Serial Visual Presentation (RSVP), in which a sequence of items is presented at the same spatial location at a rate of around 10 items per second, with each item rapidly replacing the previous one. At such speeds, the items presented, some of which are targets to be detected and others are irrelevant distractors, yield only fleeting mental representations, resulting in targets often being missed. In the AB, detection of a second target (T2) following a correctly identified first target (T1) is significantly impaired if T2 follows T1 within 200-600 ms. There has been considerable recent interest in the identification of neural correlates of the AB, and the development of neurally explicit explanations of it, a prominent one being the Simultaneous Type Serial Token (ST 2 ) [1] neural model. In addition to incorporating computationally explicit accounts of visual processing, item identification, attentional selection and working memory encoding, the model proposes the episodic distinctiveness hypothesis, i.e., that the AB reflects a system attempting to allocate unique episodic contexts to targets. Importantly, it suggests that when the visual system detects an item that may be task relevant, a spatially specific Transient Attentional Enhancement (TAE), called the ‘blaster’ is triggered. For a fleeting stimulus such as that arising in RSVP, the contribution of this enhancement is critical in enabling the stimulus to be encoded into working memory. This paper reports on our investigations into EEG activity during the AB, and a hypothesized correlation between the blaster and the N2pc ERP component [2]. The N2pc describes a negative deflection of the ERP at around 190-300 ms after the presentation of a laterally offset target, and is most strongly visible at posterior electrodes contralateral to the position of the target. Previous research has associated the N2pc with the selection of a target in the presence of competing distractors. We discuss findings that, in the context of the AB, suggest a correspondence between blaster activity and manifestation of the N2pc. Specifically, we demonstrate that the temporal firing pattern of the blaster in the model matches the N2pc component in human ERP recordings, for T1s and T2s that are seen and missed during the AB. Such a correlation between a computational account of the AB and ERP data provides useful insights into the processes underlying selectivity in temporal attention.

The Neglected Contribution of Memory Encoding in Spatial Cueing: A New Theory of Costs and Benefits

Spatial cueing is thought to indicate the resource limits of visual attention because invalidly cued items are reported more slowly and less accurately than validly cued items. However, limited resource accounts cannot explain certain findings, such as dividing attention without costs, or attentional benefits without invalidity costs. The current study presents a new account of exogenous cueing, namely the memory encoding cost (MEC) theory, which integrates attention and memory encoding to explain costs and benefits evoked by a spatial cue. Unlike conventional theories that focus on the role of attention in yielding spatial cueing effects, the MEC theory argues that some cueing effects are caused by a combination of attentional facilitation evoked by the cue, but also the cost of encoding the cue into memory. The crucial implication of this theory is that limitations in attentional deployment may not necessarily be the cause of invalidity costs. MEC generates a number of predictions that we test here, providing five convergent lines of evidence that cue encoding plays a key role in producing cueing effects. Furthermore, the MEC suggests a common mechanism underlying cueing costs and the attentional blink, and we simulate the core empirical findings of the current study with an existing attentional blink model. The model was able to simulate these effects primarily through manipulation of a single parameter that corresponds to memory encoding. The MEC theory thus simplifies our theoretical understanding of attentional effects by linking the attentional blink and some varieties of spatial cueing costs to a common mechanism.