Can Practice Overcome Age-Related Differences in the Psychological Refractory Period Effect?

Can dual-task practice remove age-related differences in the psychological refractory period (PRP) effect? To answer this question, younger and older individuals practiced 7 blocks of a PRP design, in which Task 1 (T1) required a vocal response to an auditory stimulus and Task 2 (T2) required a manual response to a visual stimulus (Experiment 1). The results showed that practice did not reduce, but rather increased, age-related differences in PRP interference. Using the trained individuals, the introduction of a less complex new T1 (Experiment 2) or a less complex new T2 (Experiment 3) with the task previously practiced reduced the PRP interference but only in older adults. The authors propose that older adults suffer from a large task-switch cost that is more sensitive to task complexity than to the amount of practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loci of signal probability effects and of the attentional blink bottleneck.

To investigate the locus of signal probability effects and the influence of stimulus quality on this locus, the authors manipulated probability in Task 2 of a psychological refractory period (PRP) paradigm. The effect was additive with stimulus onset asynchrony (SOA) when the target was not masked but underadditive with decreasing SOA when the target was masked. Even with masking, however, a range of probabilities had effects additive with SOA. The results suggest loci of stimulus probability before the PRP bottleneck as well as at or after the bottleneck. A second issue addressed was the locus of interference in the attentional blink (AB). The AB was larger when the probability of the first of 2 targets was lower. The results lead to the conclusion that one cause of the AB effect is a locus at least as late as the PRP bottleneck. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distractor devaluation effect in the attentional blink: Direct evidence for distractor inhibition.

When two targets (T1 and T2) are embedded in rapid serial visual presentation (RSVP), T2 is often missed (attentional blink, AB) if T2 follows T1 by less than 500 ms. Some have proposed that inhibition of a distractor following T1 contributes to the AB, but no direct evidence supports this proposal. This study examined distractor inhibition by assessing a distractor devaluation effect where inhibited items were evaluated less positively than controls. Experiments 1 and 2 showed that a distractor presented just after T1 was evaluated less favorably when T2 was misidentified, independently of stimulus characteristics. Experiment 3 produced distractor devaluation in T2 incorrect trials when the evaluated distractor was the second item after T1. In contrast, a distractor presented before T1 was not devaluated (Experiment 4). Experiment 5 demonstrated that participants could not recognize presented distractors after an RSVP task, rejecting the possibility that memorized distractors were devalued. Results show a relationship between the devaluation of distractors following T1 and the AB, providing the first direct evidence of the distractor inhibition during the AB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of antipredator behavior in newborn and juvenile garter snakes (Thamnophis).

Used neonate and juvenile garter snakes (Thamnophis sirtalis, T. melanogaster, and T. butleri) to investigate the role of visual stimuli in mediating antipredator behaviors and to examine the validity of techniques used to assess defensive responses. Experiment 1 demonstrated that a human hand and a model predator were more effective than other stimuli in eliciting defensive responses in neonates with no prior experience with threatening stimuli. Experiment 2 showed that yearlings responded similarly to a realistic predator model and a human hand. Experiment 3 showed that the level of antipredator behaviors was affected by stimulus size. Experiment 4 indicated that the same snakes gave similar quantitative results when tested by different experimenters with the human hand. The final study demonstrated that stimulus movement influenced defensive responses in some species but not others and found litter and experiential effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory Attentional Blink: Masking the Second Target is Necessary, Delayed Masking is Sufficient.

When two target items (T1 and T2) are presented in rapid succession among fillers, processing T2 is often impaired. This phenomenon is known as the attentional blink (AB). Within the visual modality, this second-target deficit generally occurs only if T2 is masked by a trailing item. The current study was designed to examine whether masking of T2 also plays a critical role in the auditory AB. Results showed a reliable AB effect even when the item following T2 was replaced by silence. However, the AB deficit was abolished when T2 was the last presented stimulus. Our results suggest that, as in vision, T2 masking is necessary for the AB to take place in audition, but that masking is effective even when delayed, providing evidence that the phenomenon shares some functional mechanisms across sensory modalities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition blindness has a perceptual locus: Evidence from online processing of targets in RSVP streams.

Four experiments tested whether repetition blindness (RB; reduced accuracy reporting repetitions of briefly displayed items) is a perceptual or a memory-recall phenomenon. RB was measured in rapid serial visual presentation (RSVP) streams, with the task altered to reduce memory demands. In Experiment 1 only the number of targets (1 vs. 2) was reported, eliminating the need to remember target identities. Experiment 2 segregated repeated and nonrepeated targets into separate blocks to reduce bias against repeated targets. Experiments 3 and 4 required immediate "online" buttonpress responses to targets as they occurred. All 4 experiments showed very strong RB. Furthermore, the online response data showed clearly that the 2nd of the repeated targets is the one missed. The present results show that in the RSVP paradigm, RB occurs online during initial stimulus encoding and decision making. The authors argue that RB is indeed a perceptual phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The attentional blink across stimulus modalities: Evidence for central processing limitations.

When participants are asked to report a visual target and find a subsequent visual probe, a deficit in probe report accuracy is usually found during an interval of several hundred milliseconds after the target. This attentional blink (AB) deficit has often been attributed to a uniquely visual limitation. In this research, targets and probes were created and defined in terms of auditory information. Target modality (visual or auditory) was fully crossed with probe modality (visual or auditory). In Experiment 1, a robust AB, found in all modality conditions, was equally large for cross-modality and within-modality target and probe combinations. Experiments 2 and 3 ruled out two alternative explanations for cross-modal blinks. Experiment 4 showed that as the rate of presentation was slowed, the AB for auditory probes attenuated more quickly than for visual probes. Results are discussed in terms of a central (amodal) limitation of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of phonological length on the attentional blink for words.

The authors tested whether the attentional blink (AB), a deficit in the ability to report a second target appearing within half a second of a first target, may reflect limitations for consolidating visual stimuli into working memory and awareness. Previous research has shown that people are severely limited in the rate that they can identify and report visual events presented in rapid succession. Word length was examined, a variable known to affect verbal working memory. Experiment 1 showed that the AB was modulated by the phonological length of the fast target. Phonologically longer pseudowords triggered larger blink deficits. Experiment 2 also demonstrated the word-length effect on the AB using real-world stimuli, anagrams, that controlled for low-level visual differences between conditions. These data support proposals that the AB reflects a difficulty in consolidating information into working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory mechanisms of attentional networks: Spatial and semantic inhibitory processing.

Four experiments assessed the relationships between the orienting and the executive networks of visual attention. Experiment 1 showed spatial inhibition of return (IOR) with target words. Experiment 2 showed a type of semantic inhibition that mimicked spatial IOR. Reaction times to targets preceded by 2 consecutively presented words, the prime and the intervening stimulus, were longer when the target and prime were related than when they were unrelated. Experiment 3 combined spatial and semantic inhibition in a lexical-decision task. Spatial IOR was observed with both related and unrelated targets, but semantic inhibition was observed only when target words were presented in uncued locations. A similar interaction between IOR and positive semantic priming was observed when the intervening stimulus was not presented (Experiment 4). Implications for the relationships between the 2 attentional networks are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sonification design for complex work domains: Dimensions and distractors.

Sonification—representing data in sound—is a potential method for supporting human operators who have to monitor dynamic processes. Previous research has investigated a limited number of sound dimensions and has not systematically investigated the impact of dimensional interactions on sonification effectiveness. In three experiments the authors investigated accuracy for identifying changes in six target auditory dimensions of a continuous pulse stream under three conditions: no distractor, one distractor, and five distractors. In Experiment 1 amplitude, frequency, harmonics, speed, tremolo (cycles per pulse), and width were tested. Accuracy and patterns of interaction between the dimensions were mapped. In Experiment 2 the same dimensions were tested but tremolo was operationalized as cycles per second (Hz). The patterns of interaction between the temporal dimensions differed from Experiment 1. In Experiment 3 the amplitude contour of the pulse stream was changed. The dimensions tested were amplitude, frequency, formants, speed, tremolo (cycles per period), and width. Results showed low accuracy for formants and many interactions, both positive and negative between the dimensions. The authors interpret the results in terms of theories of perceptual interference in auditory dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional requirements in visual detection and identification: Evidence from the attentional blink.

Perception of the 2nd of 2 targets (T1 and T2) is impaired if the lag between them is short (0–500 ms). The authors used this attentional blink (AB) to index attentional requirements in detection and identification tasks, with or without backward masking of T2, in 2 stimulus domains (line orientation, coherent motion). With masking, the AB occurred because T2 was masked during the attentional dwell time created by T1 processing (Experiments 1, 2, and 3). Without masking, an AB occurred only in identification because during the attentional dwell time. T2 decayed to a level that could support simple detection but not complex identification. However, an AB occurred also in detection if T2 was sufficiently degraded (Experiment 4). The authors drew 2 major conclusions: (a) Attention is required in both identification and detection, and (b) 2 factors contribute to the AB, masking of T2 while attention is focused on T1 and decay of the T2 trace while unattended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A two-stage model for multiple target detection in rapid serial visual presentation.

When 2 targets are presented among distractors in rapid serial visual presentation, correct identification of the 1st target results in a deficit for a 2nd target appearing within 200–500 ms. This attentional blink (AB; J. E. Raymond, K. L. Shapiro, & K. M. Arnell, 1992) was examined for categorically defined targets (letters among nonletters) in 7 experiments. AB was obtained for the 2nd letter target among digit distractors (Experiment 1) and also for a 3rd target (Experiment 2). Results of Experiments 3–5 confirmed that AB is triggered by local interference from immediate posttarget stimulation (Raymond et al., 1992) and showed that AB is modulated by the discriminability between the 1st target and the immediately following distractor. Experiments 5–7 further examined the effects of both local interference and global discriminability. A 2-stage model is proposed to account for the AB results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of the attentional blink during rapid serial visual presentation: perceptual interference and retrieval competition

Observers watched for 1 or 2 colored words as targets presented in lists of distractor strings (10 items/s). Identification of 1 target (T1) temporarily reduced the accuracy of reporting a 2nd target (T2). This attentional blink (AB) effect was most pronounced when T1 and T2 occurred close together in time. Use of recognition tests (instead of recall) improved performance but did not eliminate the AB effect. The AB effect was found with both word and nonword distractors, a smaller AB effect was found with consonant string distractors, and the AB effect was substantially attenuated with strings of unfamiliar characters (a false font). Analyses of errors indicated that the 2nd target is frequently replaced or corrupted by the following distractor during the blink. The AB effect appears to result from both attentional and mnemonic processes.     

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)     

Concurrent response-selection demands modulate the attentional blink.

The number of stimulus and response alternatives was varied in the 1st task of an attentional blink (AB) experiment (both tasks unspeeded) and in a speeded AB paradigm (SAB; speeded immediate response in Task?). Accuracy in Task? did not depend on the number of alternatives in the AB paradigm (Experiment 1); however, accuracy in Task? decreased as alternatives increased in the SAB paradigm (Experiments 2–3). Longer response times in Task? were associated with lower accuracy in Task?. The results suggest that the duration of central processing in Task? modulates the AB phenomenon. The results are discussed in the context of the central interference theory. The theory provides a unified theoretical framework within which the AB and SAB paradigms, the probe signal paradigm, and the psychological refractory period paradigm can be analyzed and understood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personal names and the attentional blink: a visual "cocktail party" effect

Four experiments were carried out to investigate an early- versus late-selection explanation for the attentional blink (AB). In both Experiments 1 and 2, 3 groups of participants were required to identify a noun (Experiment 1) or a name (Experiment 2) target (experimental conditions) and then to identify the presence or absence of a 2nd target (probe), which was their own name, another name, or a specified noun from among a noun distractor stream (Experiment 1) or a name distractor stream (Experiment 2). The conclusions drawn are that individuals do not experience an AB for their own names but do for either other names or nouns. In Experiments 3 and 4, either the participant's own name or another name was presented, as the target and as the item that immediately followed the target, respectively. An AB effect was revealed in both experimental conditions. The results of these experiments are interpreted as support for a late-selection interference account of the AB.     

Emotional modulation of the attentional blink: Is there an effect of stress?

Individuals are often unable to identify the second target (T2) of two when it is presented within 500 ms after the first target (T1). This “attentional blink” (AB) is attenuated by an emotionally arousing T2. Stress is known to affect cognitive performance, in particular for emotional material. In the present study, we asked whether (a) an emotional T2 reduces the AB when preceded by an emotional T1 and (b) the emotional modulation of the AB is affected by stress. Participants were presented neutral and aversive words as T1 and T2 in rapid serial visual presentation after they were exposed to stress (socially evaluated cold pressor test) or a control condition in a crossover manner. Our results indicate that an aversive T1 extends the AB. Aversive T2 attenuated the AB in the presence of a neutral, but not an aversive, T1. Stress-enhanced T2 detection and high cortisol responses to stress reduced the AB. However, neither stress nor cortisol interacted with the emotionality of the target words. In summary, these findings point to a strong impact of emotional factors on early perceptual experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An auditory repetition deficit under low memory load.

Previous studies of the auditory analogue of repetition blindness have led to different conclusions regarding the nature of the effect (e.g., N. Kanwisher & M. C. Potter, 1989; M. Miller & D. MacKay, 1994). In the present study, recall accuracy for repeated elements was examined with lists of 2 or 3 items presented dichotically under high temporal pressure. When this procedure was used, a repetition deficit in recall was obtained for both vowels (Experiment 1) and consonant-vowel syllables (Experiment 2). Further experiments demonstrated that this deficit decreases as the stimulus onset asynchrony between the 2 critical elements increases (Experiment 3) and showed that the effect also occurs for words and not just nonsense syllables (Experiment 4). In all 4 experiments, estimations of guessing biases showed that responses to unrepeated lists were not artificially favored over responses to repeated lists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The psychological refractory period effect following callosotomy: Uncoupling of lateralized response codes.

A callosotomy patient was tested in 2 dual-task experiments requiring successive speeded responses to lateralized stimuli. The patient showed a robust psychological refractory period (PRP) effect. Three aspects of the data indicate that, unlike for the control participants, the PRP effect for the split-brain patient should not be attributed to a response selection bottleneck. First, the patient did not show an increase in reaction time (RT) when the 2 tasks required responses from a common output system compared with when different output systems were used. Second, inconsistent stimulus-response mappings for the 2 tasks increased RTs for the control participants but had minimal effect on the performance of the split-brain patient. Third, the consistency manipulation was underadditive with stimulus onset asynchrony but was additive or overadditive for the normal participants. These results suggest that the persistent PRP effect following callosotomy should be attributed to a bottleneck associated with response initiation, a strategy adopted to comply with the task demands, or a combination of these factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)