Nir Shalev

The Role of Conscious Perception in Attentional Capture and Object-File Updating

A mental process that is independent of conscious perception should run equally well with or without it. Previous investigations of unconscious processing have seldom included this comparison: They typically demonstrated only processing without conscious perception. In the research reported here, we showed that attentional capture is largely independent of conscious perception and that updating the episodic information stored about an object is entirely contingent on conscious perception. We used a spatial-cuing paradigm, in which the cue was a color-singleton distractor rendered liminal by continuous flash suppression or brief exposure. When the cue matched the participant’s attentional set, it strongly captured attention whether it was subliminal or consciously perceived. In contrast, a nonmatching cue did not capture attention but instead produced a same-location cost, which was contingent on consciously perceiving the cue. Our findings demonstrate a dissociation between attention and conscious perception and unveil an important boundary condition of object-file updating.

Dissociations between developmental dyslexias and attention deficits

We examine whether attention deficits underlie developmental dyslexia, or certain types of dyslexia, by presenting double dissociations between the two. We took into account the existence of distinct types of dyslexia and of attention deficits, and focused on dyslexias that may be thought to have an attentional basis: letter position dyslexia (LPD), in which letters migrate within words, attentional dyslexia (AD), in which letters migrate between words, neglect dyslexia, in which letters on one side of the word are omitted or substituted, and surface dyslexia, in which words are read via the sublexical route. We tested 110 children and adults with developmental dyslexia and/or attention deficits, using extensive batteries of reading and attention. For each participant, the existence of dyslexia and the dyslexia type were tested using reading tests that included stimuli sensitive to the various dyslexia types. Attention deficit and its type was established through attention tasks assessing sustained, selective, orienting, and executive attention functioning. Using this procedure, we identified 55 participants who showed a double dissociation between reading and attention: 28 had dyslexia with normal attention and 27 had attention deficits with normal reading. Importantly, each dyslexia with suspected attentional basis dissociated from attention: we found 21 individuals with LPD, 13 AD, 2 neglect dyslexia, and 12 surface dyslexia without attention deficits. Other dyslexia types (vowel dyslexia, phonological dyslexia, visual dyslexia) also dissociated from attention deficits. Examination of 55 additional individuals with both a specific dyslexia and a certain attention deficit found no attention function that was consistently linked with any dyslexia type. Specifically, LPD and AD dissociated from selective attention, neglect dyslexia dissociated from orienting, and surface dyslexia dissociated from sustained and executive attention. These results indicate that visuospatial attention deficits do not underlie these dyslexias.

Assessing the temporal aspects of attention and its correlates in aging and chronic stroke patients.

Temporal dynamics of attention have been in the spotlight of research since the earliest days of cognitive psychology. Typically, researchers describe two different aspects of the temporal fluctuations of attention: one is in intervals of milliseconds (phasic alertness), and the other over minutes or even hours (tonic alertness or sustained attention). In order to evaluate individual capacities for sustained attention and phasic alertness, most studies rely on variations of the Continuous Performance Task (CPT). Indices of sustained attention and phasic alertness are typically based on reaction times to targets; phasic alertness is related to the change in reaction times following a cue, and sustained attention is related to variability of reaction times during the task. In the following study, we attempted to establish a new approach for studying sustained attention and phasic alertness, not reliant solely on reaction time measures. We developed a new variation of the CPT with conjunctive feature targets and forward and backward masking to induce a higher variability in accuracy. This allowed us to assess an individuals ability to maintain the same level of sensitivity to targets (d-prime) across a ten minute period on the task as an index for sustained attention. We also assessed reaction times as a function of previous trial type, and suggest previous trial RT benefit might be a marker for an individuals phasic alertness. We demonstrated the use of this task with healthy aging controls and stroke survivors. As a demonstration of external validity of the novel paradigm, we present a correlation between how individual performance drops over time and individual reports of distractibility in everyday life on the Cognitive Failures Questionnaire. In addition, we found significant differences between the patient and control groups in our proposed marker of phasic alertness. We discuss the implications of our study for current assessment tools, as well as general differences in phasic alertness between clinical and neurologically unimpaired groups.

Attention Functioning Among Adolescents With Multiple Learning, Attentional, Behavioral, and Emotional Difficulties

Attention-deficit/hyperactivity disorder (ADHD) is characterized by high levels of inattention, hyperactivity, and impulsivity; however, these symptoms can result from a variety of reasons. To obtain a comprehensive understanding of the various difficulties of individuals with ADHD, especially when co-occurrence difficulties are present, it is essential to combine neuropsychological and subjective assessment tools. In the present field study the authors investigated a group of adolescents with multiple deficits (MD) using neuropsychological and subjective measures. Teachers’ ratings verified extremely high levels of symptoms of oppositional behavior, inattention, hyperactivity-impulsivity, social problems, and emotional problems in this group. As expected, MD group participants showed decreased abilities to maintain attention on task for a long period of time, focus attention and effectively inhibit adjacent distractors, and resist conflicting irrelevant information. Importantly, although significant differences in the attention measures were observed at the group level, not all MD participants displayed deviant performance. Thus, we conclude that the heterogeneous group of adolescents with MD comprises individuals with primary attention deficits as well as those with other nonattentional deficits that show equivalent behavioral symptoms. Using neuropsychological tools can be useful in differentiating between different core deficits and in guiding appropriate interventions.

Manipulating perceptual parameters in a continuous performance task

Sustained attention (SA) is among the most studied faculties of human cognition, and thought to be crucial for many aspects of behavior. Measuring SA often relies on performance on a continuous, low-demanding task. Such continuous performance tasks (CPTs) have many variations, and sustained attention is typically estimated based on variability in reaction times. While relying on reaction times may be useful in some cases, it can pose a challenge when working with clinical populations. To increase interpersonal variability in task parameters that do not rely on speed, researchers have increased demands for memory and response inhibition. These approaches, however, may be confounded when used to assess populations that suffer from multiple cognitive deficits. In the current study, we propose a new approach for increasing task variability by increasing the attentional demands. In order to do so, we created a new variation of a CPT – a masked version, where inattention is more likely to cause misidentifying a target. After establishing that masking indeed decreases target detection, we further investigated which task parameter may influence response biases. To do so, we contrasted two versions of the CPT with different target/distractor ratio. We then established how perceptual parameters can be controlled independently in a CPT. Following the experimental manipulations, we tested the MCCPT with aging controls and chronic stroke patients to assure the task can be used with target populations. The results confirm the MCCPT as a task providing high sensitivity without relying on reaction speed, and feasible for patients.

Response mapping interacts with perceptual thresholds and stimulus processing speed

Traditionally, response selection is considered to reflect a separate stage of processing to visual perception. An alternative view proposes action and perception to be closely linked; however the processing stage where any cross-modal interaction would then occur remains unclear. In this study, we investigated the influence of response-mapping on a simple classification task. We presented an array of eight frames arranged in a square around a fixation point, followed by a brief presentation of an arrow in one of them (varying SOAs of 10,30,50,80 and 100ms masked). The arrow could appear in a congruent, incongruent or a neutral location with respect to its direction. Participants indicated the direction of the arrow using a response-box organized in a corresponding configuration: eight response-buttons, arranged in a square; an arrow appeared on each button. In Exp 1, the directions of the buttons matched their locations (e.g., arrow pointing right appearing on the right side); In Exp 2, the arrows and the locations were mismatched (arrow appearing on the left side, pointing right). Subsequently we manipulated the response-mapping between the locations and directions of the arrows. We changed the task to respond to locations instead of direction, in a single (Exp 3) and a dual task (Exp 5); and replicated our original experiment with different exposure times (Exp 4). In our first experiment, we observed a robust congruency effect on accuracy for arrows appearing in their matching locations. Crucially, in our following experiments, we managed to invert and manipulate this effect by changing the motor-response mapping. Using mathematical modelling according to the Theory of Visual Attention, we demonstrate that motor-mapping modulates two low-level processes independently: perceptual threshold and stimulus processing speed. We discuss the implications of multi-modal integration within a general framework of attention as a proactive cognitive function, which predicts and formulates visual percepts. Meeting abstract presented at VSS 2015.