Evidence for a response preparation bottleneck during dual-task performance: Effect of a startling acoustic stimulus on the psychological refractory period

The present study was designed to investigate the mechanism associated with dual-task interference in a psychological refractory period (PRP) paradigm. We used a simple reaction time paradigm consisting of a vocal response (R1) and key-lift task (R2) with a stimulus onset asynchrony (SOA) between 100 ms and 1500 ms. On selected trials we implemented a startling acoustic stimulus concurrent with the second stimulus to determine if we could involuntarily trigger the second response. Our results indicated that the PRP delay in the second response was present for both control and startle trials at short SOAs, suggesting the second response was not prepared in advance. These results support a response preparation bottleneck and can be explained via a neural activation model of preparation. In addition, we found that the reflexive startle activation was reduced in the dual-task condition for all SOAs, a result we attribute to prepulse inhibition associated with dual-task processing.     

The effects of multiphasic prepulses on automatic and attention-modulated prepulse inhibition

Prepulse inhibition (PPI) is widely viewed as an operational measure of sensorimotor gating. Previous research has shown that sensorimotor gating can occur automatically and also can be influenced by selective attention. The present research investigated the relationship of the transient detection response (TDR) with automatic and attention-modulated PPI using a novel “multiphasic” prepulse stimulus. Experiment 1 compared discrete versus multiphasic prepulse types in a no-task PPI protocol to validate multiphasic prepulses as effective elicitors of automatic sensorimotor gating. Results revealed that the two prepulse types elicited equivalent levels of PPI. Experiment 2 compared the effectiveness of continuous monophasic versus continuous multiphasic prepulses within a task-based PPI protocol using a lead interval of 120 ms. Results revealed a significant attention effect for monophasic prepulses only. However, robust PPI was produced by the multiphasic prepulses independent of attention as well as over time. These results suggest that multiple influences on PPI can be assessed concurrently depending on prepulse parameters designed to active the TDR when used in a PPI protocol capable of assessing the effects of selective attention on prepulse processing.     

Task-irrelevant sounds influence both temporal order and apparent-motion judgments about tactile stimuli applied to crossed and uncrossed hands

It has been suggested that judgments about the temporal–spatial order of successive tactile stimuli depend on the perceived direction of apparent motion between them. Here we manipulated tactile apparent-motion percepts by presenting a brief, task-irrelevant auditory stimulus temporally in-between pairs of tactile stimuli. The tactile stimuli were applied one to each hand, with varying stimulus onset asynchronies (SOAs). Participants reported the location of the first stimulus (temporal order judgments: TOJs) while adopting both crossed and uncrossed hand postures, so we could scrutinize skin-based, anatomical, and external reference frames. With crossed hands, the sound improved TOJ performance at short (≤300 ms) and at long (>300 ms) SOAs. When the hands were uncrossed, the sound induced a decrease in TOJ performance, but only at short SOAs. A second experiment confirmed that the auditory stimulus indeed modulated tactile apparent motion perception under these conditions. Perceived apparent motion directions were more ambiguous with crossed than with uncrossed hands, probably indicating competing spatial codes in the crossed posture. However, irrespective of posture, the additional sound tended to impair potentially anatomically coded motion direction discrimination at a short SOA of 80 ms, but it significantly enhanced externally coded apparent motion perception at a long SOA of 500 ms. Anatomically coded motion signals imply incorrect TOJ responses with crossed hands, but correct responses when the hands are uncrossed; externally coded motion signals always point toward the correct TOJ response. Thus, taken together, these results suggest that apparent-motion signals are likely taken into account when tactile temporal–spatial information is reconstructed.

     

Redundancy gains and costs in cognitive processing: effects of short stimulus onset asynchronies

In 7 experiments, the influence of varying stimulus onset asynchronies (SOAs) on the processing of redundant information about words and pseudowords was investigated. All stimuli were visually presented once or twice with 2 copies of the same item flashed either simultaneously or with short SOAs between presentations. The experiments revealed a redundancy gain for words that was absent for pseudowords. Furthermore, the redundancy gain disappeared at an SOA of 50 ms, and there was a gradual performance decline at longer SOAs. However, probing SOAs of 150 and 300 ms revealed that, compared with presentation of 1 target stimulus alone, words were processed significantly faster when target and redundantcopy appeared with a 150-ms lag. The results are tentatively explained in a neurocognitive framework.     

Precedence-effect-induced enhancement of prepulse inhibition in socially reared but not isolation-reared rats

Attention to a prepulse presented shortly before a startling stimulus enhances prepulse inhibition (PPI) of startle in normal people, but not in schizophrenics. Fear conditioning for the prepulse enhances PPI in socially reared, but not isolation-reared, rats. In humans, selective attention to acoustic signals against masking can be facilitated by precedence-effect-induced perceived spatial separation between the signal and the masker. This study investigated whether perceived spatial separation between a prepulse and a noise masker enhances PPI in socially reared rats and isolation-reared rats. The results show that both PPI and conditioning-induced PPI enhancement were larger in socially reared rats than in isolation-reared rats. More important, in socially reared, but not isolation-reared, rats, a further PPI enhancement was induced by precedence-effect-induced perceived separation between a prepulse and a masker only after the prepulse became fear conditioned. Thus, perceived separation facilitates normal rats’ attention to a conditioned prepulse and enhances PPI. Isolation rearing impairs rats’ ability to attend to ecologically significant acoustic events.     

Semantic priming and repetition priming from masked words: evidence for a center-surround attentional mechanism in perceptual recognition

Two lexical decision experiments compared semantic and repetition priming by masked words. Experiment 1 established prime-mask stimulus onset asynchronies (SOAs) with presence-absence detection judgments. Primes presented at detection-threshold SOAs produced equal facilitation for repeated and semantically related targets: 26 ms and 24 ms. Experiment 2 established SOAs with semantic judgments. Primes presented at 70% of the semantic-threshold SOA to mimic the exposure conditions of Experiment 1 produced slightly greater facilitation for repeated targets but a tendency toward inhibition for semantically related targets: 38 ms and -6 ms. These results confirm Dagenbach, Carr, and Wilhelmsen's (1989) report that strategies induced by threshold-setting tasks can influence masked priming. In addition, Experiment 2 suggests a mechanism for retrieving weakly activated semantic codes into consciousness that relies on the center-surround principle to enhance activation of sought-for codes and to inhibit related codes stored nearby in the semantic network.     

Audiotactile temporal order judgments

We report a series of three experiments in which participants made unspeeded 'Which modality came first?' temporal order judgments (TOJs) to pairs of auditory and tactile stimuli presented at varying stimulus onset asynchronies (SOAs) using the method of constant stimuli. The stimuli were presented from either the same or different locations in order to explore the potential effect of redundant spatial information on audiotactile temporal perception. In Experiment 1, the auditory and tactile stimuli had to be separated by nearly 80 ms for inexperienced participants to be able to judge their temporal order accurately (i.e., for the just noticeable difference (JND) to be achieved), no matter whether the stimuli were presented from the same or different spatial positions. More experienced psychophysical observers (Experiment 2) also failed to show any effect of relative spatial position on audiotactile TOJ performance, despite having much lower JNDs (40 ms) overall. A similar pattern of results was found in Experiment 3 when silent electrocutaneous stimulation was used rather than vibrotactile stimulation. Thus, relative spatial position seems to be a less important factor in determining performance for audiotactile TOJ than for other modality pairings (e.g., audiovisual and visuotactile).     

The time course of semantic and associative priming effects is different in an attentional blink task

When two targets are presented using rapid serial visual presentation (RSVP) and the interval between the targets is 200–500 ms, report of the second target is impaired, a phenomena known as the attentional blink (AB). This study examined the time course of semantic-only and associate–semantic priming effects during an AB task. Three RSVP experiments were conducted using targets that shared either a semantic-only or an associative–semantic relationship. The results of the three experiments demonstrated semantic-only priming effects at the shortest stimulus onset asynchronies (SOAs). Associative–semantic priming was evident at shorter and longer SOAs. This suggests that priming in an AB task is driven by conceptual overlap facilitating lexical access at short SOAs and with longer SOAs lexical access benefits from word associations links between targets.     

Visual orienting with central and peripheral precues: Deconfounding the contributions of cue eccentricity,cue discrimination and spatial correspondence

Five experiments examined effects of spatial precues on visual attention. Precues consisted of letters (X, T, O) presented bilaterally at central and peripheral locations.In the spatial correspondence conditions targets tended (p= .8) to appear on the same side as one of the letters. In the spatial translation conditions the bilateral letters were identical; one letter (e.g., X) indicated that the target would probably (p= .8) appear on the left, and the other (e.g., T) indicated that the target would probably appear on the right. In the spatial correspondence conditions (Experiments 1, 3A, 4, and 5) response latencies were quicker on valid than invalid trials, even at very brief (0 ms, 33 ms, 66 ms, 100 ms) stimulus onset asynchronies (SOAs) between cue and target onset. Also,the dynamic pattern of cost and benefit resembled that seen in previous studies with unilateral peripheral precues. In the spatial translation conditions (Experiments 2 and 3B), a clear advantage for valid trials was only apparent at somewhat longer SOAs (150 ms, 300 ms, 500 ms). Results show that the need to discriminate between cue stimuli, and the visual eccentricity of cues, are not critical factors mediating attentional effects of spatial precues. However, the presence or absence of spatial correspondence between the location of a cue stimulus and the location of the target was critically important.     

Modality-specific attention under imminent but not remote threat of shock: evidence from differential prepulse inhibition of startle

Theories of animal defensive behavior postulate that imminent, predictable threat elicits highly focused attention toward the threat source, whereas remote, unpredictable threat elicits distributed attention to the overall environment. We used threat of shock combined with measurement of prepulse inhibition of the startle reflex to test these claims in humans. Twenty-seven participants experienced periods of threat and safety. Threat and safe periods were short or long, with the short threat periods conveying relatively predictable, imminent shocks and the long threat periods conveying unpredictable shocks. Startle reflexes were elicited with equal numbers of acoustic probes presented alone, preceded by a tactile prepulse, or preceded by an auditory prepulse. We observed enhanced tactile relative to auditory prepulse inhibition during short threat periods only. This finding supports the notion that imminent threat, but not remote threat, elicits attention focused toward the relevant modality, potentially reflecting preparatory activity to minimize the impact of the noxious stimulus.     

Response priming with apparent motion primes

Response priming refers to the finding that a prime stimulus preceding a target stimulus influences the response to the following target stimulus. Typically, responses are faster and more accurate if the prime calls for the same response as the target (i.e., compatible trials), as compared with the situation where primes and targets trigger different responses (i.e., incompatible trials). However, the effect depends on presentational and temporal parameters such as the stimulus onset asynchrony (SOA) of prime and target, or prime duration. Until now, the special role of moving stimuli was largely ignored. In the present research, experiments were conducted using clearly visible moving dots as primes and static arrows as targets. Essentially, with short SOAs up to 200 ms, participants responded faster to compatible targets. In contrast, with SOAs above 200 ms, participants responded faster to incompatible targets. The results were compared with response priming with static primes. Here, a different pattern of results emerged, with faster responses to compatible than incompatible targets at a long SOA of 300 ms. Overall, the experiments provide evidence for the existence of an inhibitory mechanism in action control when (distracting) motion stimuli are present. Results could be explained with slight changes to different accounts of negative response priming effects, as well as theories of attention.     

Facial affect and temporal order judgments: emotions turn back the clock

The influence of facial affect on the perception of temporal order was examined in the context of the temporal order judgment (TOJ) paradigm. Two schematic faces were presented either simultaneously, or separated by varying stimulus onset asynchronies (SOAs; -100 ms, -34 ms, -17 ms, 17 ms, 34 ms, 100 ms), and participants had to judge which face appeared first. Each schematic face displayed one of three emotions; happy, neutral, or angry. Facial affect was found to influence judgments of temporal order at short SOAs (-17 ms, 0 ms, and 17 ms) but not at the longest SOAs (-100 ms and 100 ms), consistent with the hypothesis that facial affect influences relative onset judgments when they are difficult to make.     

Visuotactile apparent motion

This article compares the properties of apparent motion between a light and a touch with apparent motion between either two lights or two touches. Visual and tactile stimulators were attached to the tips of the two index fingers that were held apart at different distances. Subjects rated the quality of apparent motion between each stimulus combination for a range of stimulus onset asynchronies (SOAs). Subjects reported perceiving apparent motion between all three stimulus combinations. For light-light visual apparent motion, the preferred SOA and the direction threshold SOAs increased as the distance between the stimuli increased (consistent with Korte's third law of apparent motion). Touch-touch apparent motion also obeyed Korte's third law, but over a smaller range of distances, showing that proprioceptive information concerning the position of the fingers is integrated into the tactile motion system. The threshold and preferred SOAs for visuotactile apparent motion did not vary with distance, suggesting a different mechanism for multimodal apparent motion.     

What do graded effects of semantic transparency reveal about morphological processing?

We examined the influence of semantic transparency on morphological facilitation in English in three lexical decision experiments. Decision latencies to visual targets (e.g., CASUALNESS) were faster after semantically transparent (e.g., CASUALLY) than semantically opaque (e.g., CASUALTY) primes whether primes were auditory and presented immediately before onset of the target (Experiment 1a) or visual with an stimulus onset asynchrony (SOA) of 250 ms (Experiment 1b). Latencies did not differ at an SOA of 48 ms (Experiment 2) or with a forward mask at an SOA of 83 ms (Experiment 3). Generally, effects of semantic transparency among morphological relatives were evident at long but not at short SOAs with visual targets, regardless of prime modality. Moreover, the difference in facilitation after opaque and transparent primes was graded and increased with family size of the base morpheme.     

Visuotactile apparent motion

This article compares the properties of apparent motion between a light and a touch with apparent motion between either two lights or two touches. Visual and tactile stimulators were attached to the tips of the two index fingers that were held apart at different distances. Subjects rated the quality of apparent motion between each stimulus combination for a range of stimulus onset asynchronies (SOAs). Subjects reported perceiving apparent motion between all three stimulus combinations. For light—light visual apparent motion, the preferred SOA and the direction threshold SOAs increased as the distance between the stimuli increased (consistent with Korte’s third law of apparent motion). Touch—touch apparent motion also obeyed Korte’s third law, but over a smaller range of distances, showing that proprioceptive information concerning the position of the fingers is integrated into the tactile motion system. The threshold and preferred SOAs for visuotactile apparent motion did not vary with distance, suggesting a different mechanism for multimodal apparent motion.     

Selective attention fails to alter the dichotic listening lag effect: evidence that the lag effect is preattentional

Berlin et al. (1973) reported that either stimulus from a dichotic pair of consonant-vowel syllables is processed preferentially when its presentation is delayed by 30-60 ms. In the first of three experiments with 60 normal right-handed adults, we replicated the Berlin et al. "lag effect," but only for asynchronies between 60 and 90 ms. In Experiment 2 subjects focused attention selectively on one ear. The results indicated that focused attention and stimulus asynchrony have additive effects: Performance improved at the attended ear irrespective of stimulus asynchrony, but the lag effect remained unchanged relative to the divided-attention condition. Experiment 3 entailed a signal detection task that allowed separate analysis of detection and localization accuracy. As in previous studies, selective attention to one ear increased the accuracy of localization but not detection at the attended ear. Both dependent measures indicated a lag effect that remained invariant as attention was manipulated. These findings imply that the lag effect is attributable to a preattentional stage of auditory processing.     

Does temporal contiguity moderate contingency learning in a speeded performance task?

In four experiments, we varied the time between the onset of distracting nonwords and target colour words in a word-word version of the colour-word contingency learning paradigm. Contingencies were created by pairing a distractor nonword more often with one target colour word than with other colour words. A contingency effect corresponds to faster responses to the target colour word on high-contingency trials (i.e., distractor nonword followed by the target colour word with which it appears most often) than on low-contingency trials (i.e., distractor nonword followed by a target colour word with which it appears only occasionally). Roughly equivalent-sized contingency effects were found at stimulus-onset asynchronies (SOAs) of 50, 250, and 450?ms in Experiment 1, and 50, 500, and 1,000?ms in Experiment 2. In Experiment 3, a contingency effect was observed at SOAs of -50, -200, and -350?ms. In Experiment 4, interstimulus interval (ISI) was varied along with SOA, and learning was equivalent for 200-, 700-, and 1,200-ms SOAs. Together, these experiments suggest that the distracting stimulus does not need to be presented in close temporal contiguity with the response to induce learning. Relations to past research on causal judgement and implications for further contingency learning research are discussed.     

Inhibition of acoustic startle using different mechanoreceptive channels

In this experiment, we investigated the impact of vibrotactile prepulse frequency and intensity on the acoustically elicited startle response in humans. Mechanoreceptive channels differing in their sensitivity to transient stimulation have been identified in the skin. The Pacinian channel is optimally sensitive to vibrations at approximately 300 Hz and is specialized for the detection of stimulus transients, whereas the non-Pacinian I and III channels are optimally sensitive to vibrations at approximately 30 Hz. Vibrotactile prepulses with frequencies of 30 and 300 Hz and intensities of 95 and 130 mV were presented for 50 msec to the dominant hand of college students (N = 31), followed on some trials by a 95-dB broadband acoustic startle stimulus. The 300-Hz prepulses resulted in significantly more pronounced inhibition of startle magnitude, amplitude, and probability, whereas only the 30-Hz prepulses significantly facilitated blink latency. These results support the idea that the inhibition of acoustic startle is determined more by transient than by sustained aspects of vibrotactile prepulse stimuli. This study also demonstrates that different aspects of the startle response differentially reflect stimulus characteristics of the prepulse.     

Does temporal contiguity moderate contingency learning in a speeded performance task?

In four experiments, we varied the time between the onset of distracting nonwords and target colour words in a word–word version of the colour–word contingency learning paradigm. Contingencies were created by pairing a distractor nonword more often with one target colour word than with other colour words. A contingency effect corresponds to faster responses to the target colour word on high-contingency trials (i.e., distractor nonword followed by the target colour word with which it appears most often) than on low-contingency trials (i.e., distractor nonword followed by a target colour word with which it appears only occasionally). Roughly equivalent-sized contingency effects were found at stimulus-onset asynchronies (SOAs) of 50, 250, and 450 ms in Experiment 1, and 50, 500, and 1,000 ms in Experiment 2. In Experiment 3, a contingency effect was observed at SOAs of –50, –200, and –350 ms. In Experiment 4, interstimulus interval (ISI) was varied along with SOA, and learning was equivalent for 200-, 700-, and 1,200-ms SOAs. Together, these experiments suggest that the distracting stimulus does not need to be presented in close temporal contiguity with the response to induce learning. Relations to past research on causal judgement and implications for further contingency learning research are discussed.     

Interlateral asymmetry in the time course of the effect of a peripheral prime stimulus

Evidence exists that both right and left hemisphere attentional mechanisms are mobilized when attention is directed to the right visual hemifield and only right hemisphere attentional mechanisms are mobilized when attention is directed to the left visual hemifield. This arrangement might lead to a rightward bias of automatic attention. The hypothesis was investigated by testing male volunteers, wherein a "location discrimination" reaction time task (Experiments 1 and 3) and a "location and shape discrimination" reaction time task (Experiments 2 and 4) were used. Unilateral (Experiments 1 and 2) and unilateral or bilateral (Experiments 3 and 4) peripheral visual prime stimuli were used to control attention. Reaction time to a small visual target stimulus in the same location or in the horizontally opposite location was evaluated. Stimulus onset asynchronies (SOAs) were 34, 50, 67, 83 and 100 ms. An important prime stimulus attentional effect was observed as early as 50 ms in the four experiments. In Experiments 2, 3 and 4, this effect was larger when the prime stimulus occurred in the right hemifield than when it occurred in the left hemifield for SOA 100 ms. In Experiment 4, when the prime stimulus occurred simultaneously in both hemifields, reaction time was faster for the right hemifield and for SOA 100 ms. These results indicate that automatic attention tends to favor the right side of space, particularly when identification of the target stimulus shape is required.