Evoked potentials to consonant-vowel syllables

The hypothesis was tested that CV syllables (10 different consonants but the same vowel /?/) would show different evoked potential latencies and amplitudes. Differences were found which were dichotomised between plosives and other consonants. Although one difference between these two groups of consonants is the duration of that consonant, this duration difference did not adequately explain the prolonged evoked potential latencies and the reduced amplitudes for the non-plosives. However, no differences were found within the group of non-plosives, although they varied in consonant duration. It was suggested that N₁ latency and amplitude reflected processing time at an early stage of analysis of both speech and non-speech stimuli. The results show that consunants of long duration are perceived later than plosives, but well before the onset of the vowel.     

The effects of background noise on dichotic listening to consonant-vowel syllables

Lateralization of verbal processing is frequently studied with the dichotic listening technique, yielding a so called right ear advantage (REA) to consonant-vowel (CV) syllables. However, little is known about how background noise affects the REA. To address this issue, we presented CV-syllables either in silence or with traffic background noise vs. 'babble'. Both 'babble' and traffic noise resulted in a smaller REA compared to the silent condition. The traffic noise, moreover, had a significantly greater negative effect on the REA than the 'babble', caused both by a decreased right ear response as well as an increased left ear response. The results are discussed in terms of alertness and attentional factors.     

The effects of different intensity levels of background noise on dichotic listening to consonant-vowel syllables

It has previously been shown that the right ear advantage in dichotic listening to consonant-vowel syllables is affected if a background noise is presented at the same time as the dichotic stimuli. What is not known is, however, if there is also an effect of varying the intensity level of the background noise. We therefore presented conversation or traffic noise background noise simultaneously with the dichotic syllable stimuli to healthy adult subjects. The intensity of the background noises varied between 50-65 dB in steps of 5 dB. The results showed that the right ear correct reports decreased, while left ear correct reports increased as a consequence of increasing background noise intensity. The effects were also stronger for the right ear, and for the traffic background noise condition, particularly at the two highest intensity levels. The results are discussed in terms of alertness and attentional mechanisms.     

A developmental investigation of selective attention to graphic,phonetic, and semantic information in words

Second and fifth-grade and college-age subjects made similarity judgments on sets of three words that required attention to orthographic, phonetic, or semantic information. Accuracy and speed increased with age. Even the youngest subjects were able to perform the task of selecting a given feature of a word reasonably well. Differences in difficulty among the three tasks decreased with age, suggesting a developmental change (primarily between second and fifth grade) toward facility in extracting phonetic and semantic information from words. The presence of confusable, potentially relevant information had detrimental effects overall which decreased with age and varied with the type of task and type of distractor. For all ages, performance was better when all trials of a particular task were blocked together than when trials of the three tasks were randomly ordered.     

CVC syllables for investigating the phonetic sensitivity of Mandarin and English speakers

Although many individual speech contrasts pairs have been studied within the cross-language literature, no one has created a comprehensive and systematic set of such stimuli. This article justifies and details an extensive set of contrast pairs for Mandarin Chinese and American English. The stimuli consist of 180 pairs of CVC syllables recorded in two tokens each (720 syllables total). Between each CVC pair, two of the segments are identical, whereas the third differs in that a segment drawn from a "native" phonetic category (either Mandarin, English, or both) is partnered with a segment drawn from a "foreign" phonetic category (nonnative to Mandarin, English, or both). Each contrast pair differs by a minimal phonetic amount and constitutes a meaningful contrast among the world's languages (as cataloged in the UCLA Phonological Segment Inventory Database of 451 languages). The entire collection of phonetic differences envelops Mandarin and English phonetic spaces and generates a range of phonetic discriminability. Contrastive segments are balanced through all possible syllable positions, with noncontrastive segments being filled in with other "foreign" segments. Although intended to measure phonetic perceptual sensitivity among adult speakers of the two languages, these stimuli are offered here to all for similar or for altogether unrelated investigations.     

Selective attention and the acquisition of new phonetic categories

A class of selective attention models often applied to speech perception is used to study effects of training on the perception of an unfamiliar phonetic contrast. Attention-to-dimension (A2D) models of perceptual learning assume that the dimensions that structure listeners' perceptual space are constant and that learning involves only the reweighting of existing dimensions to emphasize or de-emphasize different sensory dimensions. Multidimensional scaling is used to identify the acoustic-phonetic dimensions listeners use before and after training to recognize the 3 classes of Korean stop consonants. Results suggest that A2D models can account for some observed restructuring of listeners' perceptual space, but listeners also show evidence of directing attention to a previously unattended dimension of phonetic contrast.     

How the components of speaking rate influence perception of phonetic segments

In two studies we investigated the way in which the components of speaking rate, articulation rate and pause rate, combine to influence processing of the silence-duration cue for the voicing distinction in medial stop consonants. First, we replicated the finding that the articulation rate of a carrier sentence, that is, the rate at which the speech itself is produced, influences how the duration information is used to assign voicing values. Second, and more importantly, the assignment of voicing values was also influenced by the pause rate of the sentence. Thus, the listener adjusts for both articulation rate and pause rate when processing the phonetically relevant information. Finally, the two rate components did not function in an equivalent manner, since changes in articulation rate had considerably more effect on phonetic judgments than did changes in pause rate. Alternative explanations fo the relative weighting of the two variables are discussed.     

Computerized stroop test to assess selective attention in children with attention deficit hyperactivity disorder

Research shows abnormal function of the pre-frontal cortex in Attention Deficit Hyperactivity Disorder (ADHD). This cortex is involved in the control of executive functions related to planning and execution of goal-oriented strategies, working memory, inhibitions, cognitive flexibility, and selective attention. Selective attention involves focus on the target stimulus, ignoring competing distractions. The Stroop Test (Stroop, 1935) is usually used to evaluate selective attention. This study investigated whether children with ADHD could exhibit modified performance in the Stroop Test. Using a computerized version of this test (Capovilla, Montiel, Macedo, & Charin, 2005), the study compared the reaction times (RTs) of 62 Brazilian children, between 8 and 12 years of age, 31 of whom were diagnosed with ADHD and sent to psychiatric clinics, and 31 without ADHD studying in regular schools. All children with ADHD satisfied the criteria of the DSM-IV-TR and were evaluated with the Conners Abbreviated Questionnaire (Goyette, Conners, & Ulrich, 1978), completed by parents and teachers. The results revealed that children with ADHD exhibit greater interference in RT than children without ADHD. This corroborated the hypothesis that children with ADHD exhibit a deficit in selective attention, consisting in augmented RTs, as measured by the Computerized Stroop Test.     

Spatial frequency and selective attention to spatial location

The effect of spatial attention on the detectability of gratings of different spatial frequency was measured using a probe technique. Three experiments are reported in which the detectability of full-field probe gratings was measured while subjects analyzed stimuli presented in either the central or the peripheral visual field. Selective attention to peripheral stimuli produced a facilitation at low frequencies and a decrement at high frequencies. These effects disappeared under forced-choice presentation.     

Semantic control of selective attention

Summary It is argued that at least three modes of information processing should be distinguished: (1) sensory preprocessing; (2) activation and inhibition of knowledge structures, which run parallel and are unlimited in terms of capacity; (3) activated knowledge structures are used to make behavioral decisions. Decision processes are assumed to be sequentially organized because at any moment only one unit of the activated knowledge can be taken into account. Selective attention mainly refers to the third mode of processing. In this paper, potential rules are investigated that may determine what part of the activated knowledge influences making decisions about behavior. An intuitively plausible speculation about a rule of this kind is that activated knowledge is taken into account in the order of its activation level. Certain phenomena in selective attention are related to the operation of the rule, and some data are presented that seem to favor the validity of the rule's operation in the processing of multi-element visual displays.     

Visual evoked potentials and selective attention to points in space

Visual evoked potentials (VEPs) were recorded to sequences of flashes delivered to the right and left visual fields while subjects responded promptly to designated stimuli in one field at a time (focused attention), in both fields at once (divided attention), or to neither field (passive). Three stimulus schedules were used: the first was a replication of a previous study (Eason, Harter, & White, 1969) where left- and right-field flashes were delivered quasi-independently, while in the other two the flashes were delivered to the two fields in random order (Bernoulli sequence). VEPs to attended-field stimuli were enhanced at both occipital (O₂) and central (C_z) recording sites under all stimulus sequences, but different components were affected at the two scalp sites. It was suggested that the VEP at O₂ may reflect modality-specific processing events, while the response at C_z, like its auditory homologue, may index more general aspects of selective attention.     

Attending to threat: Race-based patterns of selective attention

The present research investigated the extent to which the stereotype that young Black men are threatening and dangerous has become so robust and ingrained in the collective American unconscious that Black men now capture attention, much like evolved threats such as spiders and snakes. Specifically, using a dot-probe detection paradigm, White participants revealed biased attention toward Black faces relative to White faces (Study 1). Because the faces were presented only briefly (30-ms), the bias is thought to reflect the early engagement of attention. The attentional bias was eliminated, however, when the faces displayed averted eye-gaze (Study 2). That is, when the threat communicated by the Black faces was attenuated by a relevant, competing socio-emotional cue—in this case, averted eye-gaze—they no longer captured perceivers’ attention. Broader implications for social cognition, as well as public policies that reify these prevailing perceptions of young Black men are discussed.     

Age-related decrement in auditory selective attention

Young (n = 30), middle-aged (n = 32), and old (n = 28) adults repeated (shadowed) words presented to the left ear at 60 words per minute with and without distracter words presented to the other ear. Dichotic shadowing error rate increased with age. An attempt to eliminate the age effect by adjusting for age differences in monaural shadowing errors, fluid intelligence, and pure-tone hearing loss did not succeed. When the analyses were confined to subjects who made no monaural shadowing errors, dichotic shadowing errors still increased linearly with age. These results showed that there are selective-attention deficits in older adults that cannot be accounted for by the uncertainty of the target location.     

Probability matching in visual selective attention

Jonides (1980, p. 111) suggested a model to account for shifts of spatial attention in visual search tasks with less than 100% cue validity. This two-stage probability matching model was subsequently tested by Jonides (1983). Reaction time distribution characteristics indeed provided some support for the model. In the present paper the relevant data presented in Jonides (1980, 1981, 1983) are further analysed. The results of this analysis strongly support the probability matching hypothesis. Probability matching is apparently a very important strategic characteristic of visual spatial attention that deserves much more study.     

Stimules configuration in selective attention tasks

The possibility that perceptual configuration of stimulus elements impairs the ability to attend selectively to individual elements was tested with two-element stimuli, constructed by placing two curved lines in close proximity. Ss rapidly classified series of these stimuli which could differ on both elements or on only one with the second held constant. It was hypothesized that if the two elements formed a configuration, then Ss should have difficulty attending selectively to the element relevant for classification while filtering information from the other element. This result was obtained in one experiment with both stimulus elements oriented vertically, and it is concluded that these stimuli were perceived as unanalyzed, nominally related shapes. In another experiment, with one stimulus element oriented horizontally, selective attention to the relevant element was possible.     

Nonstrategic contributions to putatively strategic effects in selective attention tasks

Proportion compatible manipulations are often used to index strategic processes in selective attention tasks. Here, a subtle confound in proportion compatible manipulations is considered. Specifically, as the proportion of compatible trials increases, the ratio of complete repetitions and complete alternations to partial repetitions increases on compatible trials but decreases on incompatible trials. This confound is demonstrated to lead to an overestimation in the magnitude of the proportion compatible effect in the context of both a Stroop and a Simon task. Implications for previous research and directions for future research using proportion compatible manipulations are discussed.     

The role of neuromodulators in selective attention

Several classes of neurotransmitters exert modulatory effects on a broad and diverse population of neurons throughout the brain. Some of these neuromodulators, especially acetylcholine and dopamine, have long been implicated in the neural control of selective attention. We review recent evidence and evolving ideas about the importance of these neuromodulatory systems in attention, particularly visual selective attention. We conclude that, although our understanding of their role in the neural circuitry of selective attention remains rudimentary, recent research has begun to suggest unique contributions of neuromodulators to different forms of attention, such as bottom-up and top-down attention.