Coactivation in the perception of redundant targets.

Reaction time (RT) to redundant stimuli was investigated while controlling for distraction effects and response competition. In Experiment 1, a redundancy gain was found for 2 target letters with identical features (redundant) compared to trials in which 2 different targets shared the same response assignment (compatible) indicating coactivation of stimulus inputs. No difference in RTs was found between compatible displays and displays containing 2 targets with different responses (incompatible), suggesting (with other evidence) that letters were serially processed. In Experiment 2, a redundancy gain was again found. Unlike in Experiment 1, incompatible displays produced response competition, indicating a redundancy gain with parallel processing. Three forms of redundancy gains operating under specific conditions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand to mouth: Automatic imitation across effector systems.

The effector dependence of automatic imitation was investigated using a stimulus–response compatibility (SRC) procedure during which participants were required to make an open or closed response with their hand or their mouth. The correct response for each trial was indicated by a pair of letters in Experiments 1 and 2 and by a colored square in Experiment 3. Each of these imperative stimuli was accompanied by task-irrelevant action images depicting a hand or mouth opening or closing. In relation to the response, the irrelevant stimulus was movement compatible or movement incompatible, and effector compatible or effector incompatible. A movement compatibility effect was observed for both hand and mouth responses. These movement compatibility effects were present when the irrelevant stimulus was effector compatible and when it was effector incompatible, but were smaller when the irrelevant stimulus and response effectors were incompatible. Consistent with the associative sequence learning (ASL) model of imitation, these findings indicate that automatic imitation is partially effector dependent and therefore that the effector dependence of intentional imitation reflects, at least in part, the nature of the mechanisms that mediate visuomotor translation for imitation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central cross-talk in task switching: Evidence from manipulating input–output modality compatibility.

Two experiments examined the role of compatibility of input and output (I-O) modality mappings in task switching. We define I-O modality compatibility in terms of similarity of stimulus modality and modality of response-related sensory consequences. Experiment 1 included switching between 2 compatible tasks (auditory–vocal vs. visual–manual) and between 2 incompatible tasks (auditory–manual vs. visual–vocal). The resulting switch costs were smaller in compatible tasks compared to incompatible tasks. Experiment 2 manipulated the response–stimulus interval (RSI) to examine the time course of the compatibility effect. The effect on switch costs was confirmed with short RSI, but the effect was diminished with long RSI. Together, the data suggest that task sets are modality specific. Reduced switch costs in compatible tasks may be due to special linkages between input and output modalities, whereas incompatible tasks increase cross-talk, presumably due to dissipating interference of correct and incorrect response modalities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of preload of working memory on components of evoked potentials during encoding of sequentially presented letter sequences

In recent experiments with a pseudo-random sequence of 7 consonants to recall after trial (stimulus onset asynchrony 1000 ms) a reverse relationship between P300 amplitude of the event-related potential (ERP) and letter presentation position was shown (Grune et al., 1996). It was assumed that this relationship reflects competition between encoding and retention processes in this time regime. In order to find evidence for the resource competition hypothesis in working memory a 4 x 4 grid containing 4 digits preceded a sequence of 6 consonants. In the first block subjects were instructed to ignore the grid, in two remaining blocks they were asked to remember the digits or their position in the grid and to recognize them after the letter recall. In the ignore condition the expected effect of P300 decrease with letter position was found, especially at posterior electrode sites. When subjects had to process the preceding digit grid there was no position effect of P300 caused by small P300 amplitudes in the ERPs that were elicited by the first letters of the sequence. This effect was not specific to the modality of the interfering with the letter task information from the digit grid. We conclude that the grid information occupies working memory resources that are not available for the event-related processing of consonants to recall.     

Recognition memory and attentional selection: Serial scanning is not enough.

In 2 experiments with a total of 54 graduate or undergraduate students, using memory sets of up to 10 letters, the response competition paradigm was employed to investigate the extent to which extraneous visual stimuli interfere with or affect the process of memory search. It was assumed that if selective attention could exclude the effect of noise letters from a Sternberg-type (S. Sternberg; see record 1966-10810-001) memory comparison process, then there would be an increase in intercept for the reaction time (RT)–set size functions but no increase in slope. This result was obtained. However, a large difference in response times to both positive and negative set targets were found when the accompanying noise letters indicated a competing response, as opposed to when they indicated the same response as the target. It is suggested that this implies rapid identification of the nature of both target and noise, independent of a serial comparison process. A modification of a dual process model (J. F. Juola et al; see record 1972-00186-001) in which stimuli activate a familiarity value independent of memory search was suggested to account for these results. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychophysiology of P300.

The P300 component of the human average evoked potential has been associated with a host of stimulus and S variables, such as information delivery and stimulus salience. P300 is emitted by the brain in response to either attended events that are surprising or to unattended events that produce orienting. P300 does not appear to be a real-time index of signal (target) selection, since attended low-probability nonsignals also result in P300 and its latency is too long. P300 further appears to be independent of response selection; its latency therefore may or may not correlate with RT, depending on the experimental context. P300 latency does appear to index stimulus evaluation time in that it is not emitted until the stimulus has been cognitively evaluated. P300 amplitude appears sensitive to manipulations of perceptual limited capacity but not sensitive to manipulations of motor limited capacity. It has been proposed that P300's functional role in human information processing is the updating of neurocognitive models concerning future events, although other functions have also been proposed. (5 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probability effects on stimulus evaluation and response processes.

Investigated the effects of probability information on response preparation and stimulus evaluation. Eight Ss responded with 1 hand to the target letter H and with the other to the target letter S. The target letter was surrounded by noise letters that were either the same as or different from the target letter. In 2 conditions, the targets were preceded by a warning stimulus unrelated to the target letter. In 2 other conditions, a warning letter predicted that the same letter or the opposite letter would appear as the imperative stimulus with .80 probability. Correct reactions times (RTs) were faster and error rates were lower when imperative stimuli confirmed the predictions of the warning stimulus. Probability information affected (1) the preparation of motor responses during the foreperiod, (2) the development of expectancies for a particular target letter, and (3) a process sensitive to the identities of letter stimuli but not to their locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol and cognitive control: Implications for regulation of behavior during response conflict.

Alcohol intoxication often leads to dysregulated behavior in contexts characterized by conflict between prepotent response tendencies and incompatible alternative responses. Recent research has identified 2 components of an anterior executive attention system that are essential for adaptive behavior when response conflict exists. Event-related potential (ERP) measures of evaluative and regulative cognitive control were collected to determine if impaired executive attention was responsible for observed behavior deficits when intoxicated. Intoxicated participants displayed task performance deficits on incongruent color-naming trials relative to sober controls. Alcohol did not affect P3 magnitude/latency, indicating that timing and integrity of stimulus evaluation remained intact. In contrast, alcohol did reduce frontal components of ERP that index evaluative and regulative cognitive control processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of voluntary expectancies on reaction times and event-related potentials: Evidence for automatic and controlled expectancies.

Expectancy has been used to explain the effects of stimulus sequences both on reaction times (RTs) and on the P300 component of the human event-related potential. However, there are conflicting views about the control obtainable over these underlying expectancies. The effects of voluntary expectancies for stimulus changes or repetitions in random tone series on RTs and the P300 were compared. Ss responded according to either stimulus identity (Exp 1) or stimulus sequence (Exp 2). In both experiments, RTs were strongly affected by event expectedness. P300 amplitude, on the other hand, was affected (as a trend) only in Exp 2. Results suggest that there are at least 2 types of "expectancy," one that is largely automatic and inflexible, reflected in P300 amplitude, and a second, controlled process that is reflected mainly in RT. The latter type of expectancy appears to affect processing stages beyond stimulus evaluation and classification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shifting attention between global features and small details: an event-related potential study

In two experiments, large letters H or Z composed of small letters (also H or Z) were presented. Subjects had to make a two-choice motor response (e.g. H--left key, Z--right key). A cue presented 500 ms before the letter indicated which level (global or local) was relevant. In Experiment I, a third letter (T) sometimes appeared either at the cued or the non-cued level; in the former case, subjects had to shift their attention and to respond to stimulus features located at the non-cued level. The interference effect (RT delay in response to incongruent stimuli as compared to congruent ones) was larger when the local, rather than global, level was cued. A slow anterior negativity preceding globally-cued stimuli and shorter N1 and P2 ERP component latencies to these stimuli indicated better preparation for processing of global, as compared to local, stimulus features. The shift from local to global focus yielded a larger increase of RT, error rate, and of the P600 latency than the global-to-local shift. The P600 latency changes were parallel to those of RT. In Experiment II, the attentional shift was provoked by stimulus color red-colored letters meant that the cue was invalid, and thus, subjects had to respond to the non-cued level. Neither the interference nor the attentional shift demonstrated any asymmetry between the global and local levels. ERPs also did not differ substantially after local and global cues. In the condition demanding a shift of focus (invalid cue, incongruent letter), a positive deflection of the lateralized readiness potential indicated the activation of the wrong response channel. The large RT increment in this condition was not accompanied by an increase of the P600 latency. Two possible mechanisms of attentional shift may be proposed, the first related to perceptual processes (e.g. an additional visual search), and the second, to the competition between two response intentions.     

Premonitions of insight predict impending error.

Five experiments with approximately 266 college students explored the dynamic metacognitions that accompany the problem- and anagram-solving processes. Ss repeatedly rated how warm or close they were to solution. High feelings of warmth before an answer indicated that the answer would be incorrect. Moderately low warmth ratings characterized correct responses. The data suggest that the high warmth ratings may result from a process wherein Ss convince themselves that an inelegant but plausible (wrong) answer is correct. No gradual rationalization process precedes the correct response to insight problems. The warmth-rating data also indicate that when the correct answer was given to the problems and anagrams used in this study, there was usually a subjectively catastrophic insight process. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does motion-induced grouping modulate the flanker compatibility effect?: A failure to replicate Driver & Baylis.

Three experiments involving a total of 36 undergraduates required Ss to make a speeded decision about a central target letter embedded in a 5-letter string. On each trial the identity of the near or far letters was either compatible or incompatible with the correct response, while the remaining letters were neutral. In contrast to the findings of J. Driver and G. C. Baylis (see record 1990-00258-001), when the far distractors and the target moved together while the near distractors remained stationary, it was not found that the flanker compatibility effect (FCE) of the far distractors was greater than the FCE for the stationary near distractors. The pattern of response latencies in this moving condition were not different from what was observed when all letters remained stationary. Accuracy was affected, but not in the direction predicted by the view that attention is directed to perceptual groups. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus intensity on the lateralized readiness potential.

Information-processing models differ about whether stimulus intensity affects the speed of motor processes involved in response activation and execution. Previous studies of intensity are reviewed, but they are not decisive on this point because they have used indirect approaches requiring strong assumptions. Two experiments examined the effects of stimulus intensity on the lateralized readiness potential (LRP), a measure of hand-specific response activation. In Experiment 1, visual stimulus intensity influenced the time from stimulus onset to LRP onset but not the time from LRP onset to the keypress response. In Experiment 2, auditory stimulus intensity did not influence either of these time intervals, although it did influence the time from stimulus onset to the N100 and P300 components of the evoked potential. The results indicate that stimulus intensity does not influence the duration of motor processes in choice reaction time tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attentional delays and attentional capture among simultaneous visual onset elements

Visual discrimination and detection responses to a single stimulus presented simultaneously with noise stimuli are slower and less accurate than are responses to a single stimulus presented alone. This occurs even though the location of the relevant stimulus (target) is known or visually indicated with stimuli onset. Results showed that noise elements delay focal attending and processing of a target. Furthermore, precuing the target location reduces, and can eliminate, target processing delays. Processing delays were not due to response competition or to random attentional capture by noise. It is suggested that simultaneous stimuli are perceived initially as a single object, and delays in processing a single stimulus are due to difficulties in perceptually segregating this stimulus from noise. Precuing is assumed to facilitate this segregation process.     

Persistence of negative priming: Steady state or decay?

Responses to recently ignored stimuli may be slower and less accurate than responses to new stimuli. W. T. Neill and R. L. Westberry (1987) found that such negative priming effects dissipated within a 2-sec interval between response and the next stimulus, the response–stimulus interval (RSI). However, experiments by S. P. Tipper et al, (1991) found negative priming persisted unchanged over RSIs from 1,350 to 6,600 msec. The current experiments used a letter-matching procedure in which target letters were flanked by irrelevant letters. Negative priming was manifested by longer reaction times (RTs) and more errors to letters that had appeared as flankers in the preceding trial. RSI was varied from 500 to 8,000 msec. Negative priming diminished over the RSI, particularly within the 1st sec. This effect did not depend on the presence or absence of temporal uncertainty or on Ss' awareness of intertrial relations. An episode retrieval theory to account for negative priming phenomena is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An accrual model for primed digit classification.

This article describes a chronometric experiment of digit classification with masked primes. EEG experiments have shown that the subliminal prime activates the cortex prior to the target signal, thusly modifying the response: Congruent primes lead to faster correct answers, while incongruent primes result in slower response. It is noticed that incorrect answers show an inverted effect: A congruent prime inhibits incorrect answers, and the reverse for incongruent primes. Within the evidence accrual paradigm, it is suggested that the prime activity in the motor cortex effectively behaves as a shift in the decision threshold. This model assumption is consistent with our experimental findings. The correct and incorrect answers and the error percentage are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of automatic imitation is sensitive to sensorimotor contingency.

The associative sequence learning model proposes that the development of the mirror system depends on the same mechanisms of associative learning that mediate Pavlovian and instrumental conditioning. To test this model, two experiments used the reduction of automatic imitation through incompatible sensorimotor training to assess whether mirror system plasticity is sensitive to contingency (i.e., the extent to which activation of one representation predicts activation of another). In Experiment 1, residual automatic imitation was measured following incompatible training in which the action stimulus was a perfect predictor of the response (contingent) or not at all predictive of the response (noncontingent). A contingency effect was observed: There was less automatic imitation indicative of more learning in the contingent group. Experiment 2 replicated this contingency effect and showed that, as predicted by associative learning theory, it can be abolished by signaling trials in which the response occurs in the absence of an action stimulus. These findings support the view that mirror system development depends on associative learning and indicate that this learning is not purely Hebbian. If this is correct, associative learning theory could be used to explain, predict, and intervene in mirror system development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality, reaction time, and event-related potentials.

Reaction time (RT), movement time (MT), and the amplitude and latency of the P300 ERP were recorded from 30 Ss during the performance of 6 simple cognitive tasks. Extraversion was negatively associated with MT, a result that endorses the view that extraversion is determined, in part, by individual differences in motor mechanisms. Higher neuroticism scores were associated with faster P300 latency, a measure that is regarded as an index of stimulus evaluation time that is independent of response production. Paradoxically, higher neuroticism scores were associated with slower RT, a measure that is also regarded as an index of speed of information processing. Higher psychoticism scores were associated with smaller P300 amplitude, an effect that may be indicative of less attentional effort invested in the tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning as accumulation: A reexamination of the learning curve.

Theories of learning that predict a negative exponential growth curve are based on the assumption that learning is a process of replacement—incorrect response tendencies are replaced with correct ones. In the present article, an alternate model is presented that describes learning as a process of accumulation where incorrect response tendencies remain constant and correct response tendencies increase with practice. These 2 approaches were compared in their ability to describe the shapes of the learning curves for several experiments in free recall and perceptual and motor learning. In nearly every case, the predictions of the accumulation model were superior, and the predictions of the best fitting replacement equations failed in systematic ways. The relationship between the accumulation model and a reinforcement theory of steady-state responding is discussed. It is argued that the accumulation model should be given greater consideration as a viable model of the learning process. (68 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Letter encoding in visual word identification: More evidence for a word-integration explanation for parafoveal preview effects in reading.

A letter string presented briefly in the parafovea facilitates naming a foveally presented word provided that the two stimuli are orthographically similar. The facilitation is asymmetrical in that to obtain it, both letter strings must have the first letters in common. One possible explanation, a letter-integration hypothesis, proposes that readers only identify the letters at the beginning of the parafoveal stimulus, an action that facilitates processing the target. Another explanation, a word-integration hypothesis, postulates that all the letters of the parafoveal stimulus are identified and that the asymmetry occurs because the first letters of the parafoveal stimulus are weighted more heavily than the later ones. The two accounts differ in the way the position of the first letter is determined. To distinguish the views, English and Hebrew stimuli were presented to 7 bilingual readers. 12 normal students participated as controls. Readers could not anticipate the position of the first letters; hence, if the letter-integration explanation is correct, the asymmetry in the priming should be attenuated. Consistent with the word-integration explanation, however, priming occurred when the target shared the beginning letters with the prime in both languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)