W. Trammell Neill

Information processing and PTSD: a review of the empirical literature.

This article reviews a series of studies that have utilized information-processing paradigms with posttraumatic stress disorder (PTSD) populations. The review suggests that pretrauma measures of intelligence (IQ) are predictive of the development of PTSD symptoms following trauma. There is also evidence of impaired performance on standardized tests of memory (independent of IQ) in PTSD populations. PTSD populations are found to exhibit deficits in memory function that may be due to hippocampus damage secondary to excessive neuroendocrine responses to conditioned stimuli. In addition, individuals with PTSD evince an attentional bias towards trauma-related stimuli at postrecognition stages of information processing. The review also includes that there is insufficient evidence to either support, or reject, the theoretical proposition that PTSD patients are sensitive to global valence effects at the earliest stages of information processing relative to traumatized non-PTSD populations. Finally, there is some evidence to suggest that the processes associated with autobiographical memory in PTSD populations are similar to those seen in depression. The implications of these findings for the behavioral and cognitive treatment of PTSD are discussed. Directions for future research with such paradigms are also discussed in light of contemporary information processing theories of PTSD.

Persistence of negative priming: Steady state or decay?

Responses to recently ignored stimuli may be slower and less accurate than responses to new stimuli. Neill and Westberry (1987) found that such negative priming effects dissipated within a 2-s interval between response and the next stimulus, the response-stimulus interval (RSI). However, experiments by Tipper, Weaver, Cameron, Brehaut, and Bastedo (1991) found negative priming persisted unchanged over RSIs from 1,350 to 6,600 ms. Our experiments used a letter-matching procedure in which target letters were flanked by irrelevant letters. Negative priming was manifested by longer reaction times and more errors to letters that had appeared as flankers in the preceding trial. RSI was varied from 500 to 8,000 ms.

Selective attention and the inhibitory control of cognition.

Publisher Summary This chapter reviews the empirical evidence for inhibitory mechanisms in attention and their theoretical implications. Natural environments offer multiple sources of information that could potentially control human behavior. Yet humans respond to only some limited subset of those sources, and selected, goal-appropriate objects and events are referred to as “attended,” whereas the remaining sources of information are “ignored.” Inhibition of irrelevant processing appears to be an important function of selective attention. This new perspective has important implications for real-world cognitive functioning. Subject populations that are distinguished either clinically or developmentally by cognitive deficits are often unable to inhibit certain kinds of distracting information. Responses to an object may be slower and/or less accurate if a related object has recently been ignored. This negative-priming effect has been demonstrated for many different kinds of stimulus materials, vocal and manual response modes, and a wide variety of judgments including identification, classification, matching, counting, and localization.

MECHANISMS OF ATTENTION

Publisher Summary The concept of attention lies at the very core of cognitive psychology. Some people consider this concept to be the primary feature distinguishing the cognitive school from classical behavior theory. According to some classic theories of learning, any conditionable stimulus that reliably precedes a conditionable response by a short amount of time will come to elicit that response. Such theories regard people and animals as passive receivers and transformers of information from the environment. This chapter presents an analysis on the concept of attention, the two kinds of processing limitations of brain, and the illustrative difficulties for single-channel theory. The central assumption in single-channel theory is a processing limitation in translating information in the sensory buffer to long-term memory. The information in long-term memory may be the name of the stimulus, the meaning of the stimulus, or some other information, such as the response to be made to the stimulus. The general question that emerges is whether more than one signal has simultaneous and unimpaired access to signal-related information stored in memory. The chapter also discusses processing multiple signals and the problem of stimulus integrality.

Does inhibition of return occur in discrimination tasks

When attention is drawn to a location and then withdrawn, responding to a stimulus at that location may be slower than to one at a new location. This “inhibition of return” (IOR) has not been reliably demonstrated in tasks that require discrimination of targets from nontargets. The present experiments replicated IOR in detection and localization tasks only when target/nontarget discrimination was not also required. When discrimination was required, a consistent samelocation advantage occurred for repeated targets. Changed targets may, however, induce a bias toward opposite responses. The results cast doubt on IOR as a general attentional phenomenon.

Negative priming without probe selection.

Responses to an object may be slower or less accurate if that object shares attributes with a recently ignored object(negative priming). Some studies have found negative priming only if the probe trial required selection against a distractor stimulus. In the present experiment, subjects responded to the location of a target (O), ignoring a distractor (X) if it appeared in another location. Reaction time was slower to probe targets that appeared in the same location as the prime distractor, regardless of whether or not the probe target was accompanied by a distractor.

Negative priming insame-different matching: Further evidence for a central locus of inhibition

Responses to recently ignored information may be slower or less accurate than responses to information not recently encountered. Such negative priming effects imply that the mechanism of selective attention operates on unattended, as well as attended, information. In the present experiment, subjects judged the second and fourth letters of five-letter strings (e.g., BABAB) as “same” or “different.” Responses were slower when a target letter was identical to the distractors presented in the immediately preceding trial. This effect did not depend on which response was required on the current or preceding trial. The results suggest that ignored information is functionally disconnected from the response system as a whole, rather than from a specific response.

Switching attention within and between categories: Evidence for intracategory inhibition

In a variation of the Posner and Snyder (1975b) paradigm, subjects made speeded “same” or “different” responses to pairs of digits or letters on the basis of name identity (Experiment 1) or physical identity (Experiment 2). Each target pair was preceded by an informative (letter or digit) or noninformative (plus-sign) warning signal. The letter or digit represented by an informative warning signal had a high probability of appearing in the subsequent target pair (expected condition). On trials in which the expected stimulus did not appear in the target pair, the target pair belonged with equal probability to either the same category (either letters or digits) as the expected stimulus or to the opposite category (unexpected-similar and unexpected-opposite conditions, respectively). The pattern of “benefits” and “costs” of attentional expectancy found by Posner and Snyder for “same” responses was replicated: Subjects were faster and more accurate in the expected condition than in the neutral (uninformative warning signal) condition, but slower and less accurate in the unexpected conditions. Present theoretical interest concerns “same” response times and accuracy for the two unexpected conditions. Under instructions emphasizing accuracy as well as speed (Experiments 1 and 2), performance was worse in the unexpected-similar condition than in the unexpected-opposite condition. Only when instructions deemphasized accuracy (Experiment 2) was performance better in the unexpected-similar condition than in the unexpected-opposite condition. The fact that subjects may have more difficulty switching attention within a category than between categories (at least when instructions emphasize accuracy as well as speed) contrasts sharply with current theoretical emphasis on intracategorical facilitation effects in the priming paradigm. The results are interpreted within the framework of a model of attention (Keele & Neill, 1978) in which the activation of associates to the focus of attention is actively and optionally suppressed so as to reduce present or potential interference with the focal information processing.

Masking by Object Substitution: Dissociation of Masking and Cuing Effects

In a newly discovered form of visual masking, a target stimulus is masked by 4 flanking dots if their offset is delayed relative to the target (V. Di Lollo, J. T. Enns, & R. A. Rensink, 2000). In Di Lollo et al. (2000), the dot pattern also cued the relevant target and therefore required deliberate attention. In the present Experiments 2-6, a central arrow cued 1 of 2 letters for an E/F discrimination, with dots flanking both letters. Masking was reduced compared with the mask-cue procedure but was still robust. Delayed-offset dots flanking the nontarget also impaired performance, indicating competition for attention. Masking was unaffected by brightness of the dots relative to the target. Masking was attenuated not only by precuing attention to the target location but also by preview of an uninformative dot mask. Theories of masking by object substitution must therefore accommodate the prior context into which the target stimulus is introduced.

RESPONSE CONFLICT REVERSES PRIMING : A REPLICATION

Subjects named target words that followed a masked prime word of 33-msec (Experiments 1A and 1B) or 200-msec (Experiment 2) duration. The target word was either presented alone or accompanied by an interleaved distractor word. Targets presented alone were named more quickly following an identical prime than following an unrelated prime (repetition priming). In Experiment 1A, targets with distractors were named more slowly following an identical prime than following an unrelated prime (negative priming), replicating Milliken, Joordens, Merikle, and Seiffert (Psychological Review, 1998). In Experiments 1B and 2, repetition priming was reduced, although not reversed, for targets with distractors. The results of all three experiments are opposite to the usual finding of enhanced priming for perceptually degraded targets and suggest that response conflict engages retrospective mechanisms that counteract the facilitatory effects of priming.