Perception of dynamic information for vowels in syllable onsets and offsets

It has been demonstrated using the “silent-center” (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets,taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsetsalone or syllable offsetsalone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable off-sets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as “front” or “back” was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

Attentional capture by onsets and offsets

Three experiments were conducted to examine whether human infants would form a categorical representation for the spatial relation between. Experiment 1 showed that 6- and 7-month-olds familiarized with stimuli depicting a diamond in different locations between two reference bars subsequently preferred a stimulus displaying the diamond located outside the bars over a stimulus displaying the diamond located in a novel position between the bars. Experiments 2 and 3 revealed that this preference could not be attributed to a failure to discriminate the location changes of the diamond between the bars or an a priori preference. The overall pattern of results indicates that 6- and 7-month-olds had formed a categorical representation for between. The findings are discussed in terms of factors affecting development of categorical representations for spatial relation information.     

Attention capture by contour onsets and offsets: No special role for onsets

In five experiments, we investigated the power of targets defined by the onset or offset of one of an object’s parts (contour onsets and offsets) either to guide or to capture visual attention. In Experiment 1, search for a single contour onset target was compared with search for a single contour offset target against a static background of distractors; no difference was found between the efficiency with which each could be detected. In Experiment 2, onsets and offsets were compared for automatic attention capture, when both occurred simultaneously. Unlike in previous studies, the effects of overall luminance change, new-object creation, and number of onset and offset items were controlled. It was found that contour onset and offset items captured attention equally well. However, display size effects on both target types were also apparent. Such effects may have been due to competition for selection between multiple onset and offset stimuli. In Experiments 3 and 4, single onset and offset stimuli were presented simultaneously and pitted directly against one another among a background of static distractors. In Experiment 3, we examined “guided search,” for a target that was formed either from an onset or from an offset among static items. In Experiment 4, the onsets and offsets were uncorrelated with the target location. Similar results occurred in both experiments: target onsets and offsets were detected more efficiently than static stimuli which needed serial search; there remained effects of display size on performance; but there was still no advantage for onsets. In Experiment 5, we examined automatic attention capture by single onset and offset stimuli presented individually among static distractors. Again, there was no advantage for onset over offset targets and a display size effect was also present. These results suggest that, both in isolation and in competition, onsets that do not form new objects neither guide nor gain automatic attention more efficiently than offsets. In addition, in contrast to previous studies in which onsets formed new objects, contour onsets and offsets did not reliably capture attention automatically.     

Oculomotor consequences of abrupt object onsets and offsets: onsets dominate oculomotor capture

Previous research has shown that the appearance of an object (onset) and the disappearance of an object (offset) have the ability to influence the allocation of covert attention. To determine whether both onsets and offsets have the ability to influence eye movements, a series of experiments was conducted in which participants had to make goal-directed eye movements to a color singleton target in the presence of an irrelevant onset/offset. In accord with previous research, onsets had the ability to capture the eyes. The offset of an object demonstrated little or no ability to interrupt goal-directed eye movements to the target. Two experiments in which the effects of onsets and offsets on covert attention were examined suggest that offsets do not capture the eyes, because they have a lesser ability to capture covert attention than do onsets. A number of other studies that have shown strong effects of offsets on attention have used offsets that were uncorrelated with target position (i.e., nonpredictive), whereas we used onsets and offsets that never served as targets (i.e., antipredictive). The present results are consistent with a new-object theory of attentional capture in which onsets receive attentional priority over other types of changes in the visual environment.     

The effects of onsets and offsets on visual attention

 Two experiments are presented which examine the effect of onset and offset cues on early occurring attentional cueing effects and later occurring inhibition of return (IOR). The first experiment compared the effects of single onset cues, single offset cues, and simultaneous onset and offset cues (at opposite locations) at a 100-ms stimulus-onset-asynchrony (SOA) and IOR at a 900-ms SOA. Whereas the first experiment examined these conditions with choice localization keypress responses, the second experiment used simple detection keypress responses. Both experiments found that onset and offset cues presented in isolation produce early facilitation and late IOR. When onset and offset cues were simultaneously presented, facilitation but not IOR was found with localization responses, while neither facilitation or IOR was found with detection responses. Overall, these findings suggest that offset cues can be treated in the same manner as onset cues by the attentional system, although the onset cues may have priority in orienting attention when targets must be localized in space. Received: 26 May 2000 / Accepted: 31 January 2001     

Contingent capture for onsets and offsets: attentional set for perceptual transients

Four experiments were conducted to examine whether attentional set affects the ability of visual transients (onsets and offsets) to capture attention. In the experiments, visual search for an identity-defined target was conducted. In the first 3 experiments, the target display either onset entirely or was revealed by offsetting camouflaging line segments to reveal letters. Prior to the target display, there was a noninformative cue, either an onset or an offset, at one of the potential target locations. Cues that shared the same transient feature as the target display captured attention. The lack of predictable target transients led to attentional capture by all forms of transients. The final experiments with luminance changes without offsets or onsets showed attentional capture when the luminance changes were large. The results suggest that attentional set can be broadly or narrowly tuned to detect changes in luminance.     

Spatial correspondence between onsets and offsets of stimuli and responses

The Simon effect denotes faster responses when the task-irrelevant stimulus position corresponds to response position than when it does not. A common explanation is that a spatial stimulus code is formed automatically and activates a spatially corresponding response code. Previous research on stimulus–response (S–R) compatibility has focused on the ability to initiate movements to stimulus onsets. The present study investigates spatial-compatibility effects (i.e., the Simon effect) in the ability to initiate and to terminate actions both to stimulus onsets and to stimulus offsets. There were four major results. Firstly, offset stimuli produced normal Simon effects suggesting that stimulus offsets can automatically produce spatial codes. Secondly, onset stimuli produced larger Simon effects than offset stimuli, which is consistent with the attention-shift account of spatial coding. Thirdly, Simon effects were also observed in action termination. Fourthly, Simon effects in action initiation and in action termination were of similar size.     

The control of attention by abrupt visual onsets and offsets

A letter can be presented visually either by the abrupt appearance of lines that make up the letter (onset transient) or by the abrupt disappearance of extra lines from a form in which the letter is embedded (offset transient). Recent evidence from visual-search tasks has suggested that onset transients have absolute priority over offset transients with respect to the allocation of visual attention. Specifically, these studies have found that a single onset-transient target letter pops out of a background of offset-transient distractor letters (i.e., time to detect the target is independent of the number of distractors), which indicates that attention is automatically directed to the location of an onset-transient stimulus even when there are competing offset transients (Yantis & Jonides, 1984). Because of the way the offset letters were created, however, the total display change (number of offset line-segments plus number of onset line-segments) was greater for onset than for offset letters. Thus, onset targets might have popped out because they produced greater overall display changes rather than because they were the only letters with onset transients. In the present study, a figure that included more offset-transient line segments in the offset-transient letters was used. Under these conditions, onset-transient targets did not pop out of a background of offset-transient distractors. It is suggested that visual attention may be influenced by total display change and, therefore, that onset transients are not necessarily sufficient to control attention when there are many competing offset transients.     

Color onsets and offsets, and luminance changes can cause change blindness

It has recently been demonstrated that people often fail to detect between-view changes in their visual environment. This phenomenon, called 'change blindness' (CB), occurs whenever the perceptual transient that usually accompanies a change is somehow blocked, or made less salient. In the well-known flicker paradigm, the transient is blocked by inserting a blank screen between the original and changed scenes. We tested whether transients that do not involve the appearance or disappearance of visual objects would also produce CB. Therefore we tested whether the appearance or disappearance of color information, and increments or decrements in luminance, could cause CB. In three experiments, subjects searched for changes in natural scenes. We found that both color transients and luminance transients significantly reduced change detection (by approximately 30%) relative to a no-transient condition.     

Perception of dynamic information in static handwritten forms

Handwriting recognition presents a problem for most theories of letter perception. How do people accurately discriminate letters given the variability in handwritten forms? We propose that perceivers detect and capitalize on information relating to production inherent in the static trace of the handwritten letter. In an "implicit detection" task, subjects' ability to detect stroke direction in a series of handwritten characters was found to be influenced by the particular drawing method used to generate the stimuli. Similar results were obtained in an "explicit detection" task in which the subjects were asked to speculate on the drawing method used to generate the samples. Our findings suggest that perceivers are able to extract information relating to production from the static trace. We propose that they can then use this information in conjunction with their knowledge of a common production process, shared by both producers and perceivers, to aid character recognition.     

Exogenous and endogenous control of attention: the effect of visual onsets and offsets

Two experiments were carried out to investigate the relation between exogenous and endogenous control of visual attention. Subjects searched for a target letter among three nontarget letters that were positioned on an imaginary circle around a fixation point. At different cue-display intervals, a centrally located arrowhead cue reliably indicated the location of the target letter. At different SOAs, a peripheral line segment near one of the letters was either abruptly switched on (Experiment 1) or abruptly switched off (Experiment 2). Presenting the central arrowhead after display onset prevents attention from being focused in advance on the critical location. In this unfocused attentional state, both onset and offset transients attracted attention. When the central arrowhead was available in advance, the focusing of attention prior to display onset precluded attention attraction to the location of the onset or offset transient. Contrary to an offset transient, an onset transient presented at the attended location disrupted performance, indicating that an onset within the spotlight of attention attracts attention. The results are reconciled by means of the zoom-lens theory of attention, suggesting that outside the focus of attention, abrupt transients are not capable of attracting attention. Since the size of the zoom lens is under voluntary control, it can be argued that transients do not fulfill the intentionality criterion of automaticity.     

Better late than never: how onsets and offsets influence prior entry and exit

The three experiments presented in the paper examine visual prior entry (determining which of two stimuli appeared first) and prior exit (determining which of two stimuli disappeared first) effects with a temporal order judgment (TOJ) task. In addition to using onset and offset targets, the preceding cues also consisted of either onset or offset stimuli. Typical, and equivalent, prior entry effects were found when either onset or offset cues preceded the onset targets. Unexpectedly large prior exit effects where found with the offset targets, with offset cues producing greater capture effects than onset cues. These findings are consistent with the notion that more attention is allocated to searching the visual field when targets are more difficult to find. In addition, the results indicate that attentional control settings may be more likely to occur with more difficult searches. In addition, these findings demonstrate that TOJ tasks provide extremely precise measures of the allocation of attention and are very sensitive to a range of task manipulations.     

Perception of synthetic nasal consonants in initial and final syllable position

Identification and discrimination of synthesized syllable-initial and syllable-final nasal consonants (/mæ-næ-ηæ/ and æm-æn-æη) by adult American subjects were assessed to determine (1) whether place-of-articulation contrasts in nasals, cued only by second and third formant transition variations, were perceived categorically, and (2) if linguistic experience affected_ the perception of this acoustic dimension. In two experiments, subjects produced consistent identification functions with sharp boundaries between familiar phoneme categories. Corresponding discrimination functions showed “peaks” of relatively accurate perception for cross-category comparison pairs, indicating categorical perception. Identification consistency and discrimination accuracy were inferior for the/n/-/η/ contrast in the unfamiliar (and phonologically inappropriate) syllable-initial condition compared to the familiar syllable-final condition. No such difference was found in identification and discrimination of the acoustically comparable oral stop consonant contrast/d/-/g/in syllable-initial and syllable-final position. These results provide evidence that perception of linguistically relevant acoustic dimensions by adults is constrained, at least in part, by their familiarity with those acoustic (and phonetic) contrasts in specific phonological contexts.     

Attentional guidance of the eyes by contextual information and abrupt onsets.

Contextual cuing is a memory-based phenomenon in which previously encountered global pattern information in a display can automatically guide attention to the location of a target (Chun & Jiang, 1998), leading to rapid and accurate responses. What is not clear is how contextual cuing works. By monitoring eye movements, we investigated the roles that recognition and guidance play in contextual cuing. Recognition does not appear to occur on every trial and sometimes does not have its effects until later in the search process. When recognition does occur, attention is guided straight to the target rather than in the general direction. In Experiment 2, we investigated the interaction between memory-driven search (contextual cuing) and stimulus-driven attentional capture by abrupt onsets. Contextual cuing was able to override capture by abrupt onsets. In contrast, onsets had almost no effect on the degree of contextual cuing. These data are discussed in terms of the role of top-down and bottom-up factors in the guidance of attention in visual search.     

Perceptual parsing of acoustic consequences of velum lowering from information for vowels

Three experiments were designed to investigate how listeners to coarticulated speech use the acoustic speech signal during a vowel to extract information about a forthcoming oral or nasal consonant. A first experiment showed that listeners use evidence of nasalization in a vowel as information for a forthcoming nasal consonant. A second and third experiment attempted to distinguish two accounts of their ability to do so. According to one account, listeners hear nasalization in the vowel as such and use it to predict that a forthcoming nasal consonant is nasal. According to a second, they perceive speech gestures and hear nasalization in the acoustic domain of a vowel as the onset of a nasal consonant. Therefore, they parse nasal information from a vowel and hear the vowel as oral. In Experiment 2, evidence in favor of the parsing hypothesis was found. Experiment 3 showed, however, that parsing is incomplete.     

Relative salience of syllable structure and syllable order in zebra finch song

There is a rich history of behavioral and neurobiological research focused on the ‘syntax’ of birdsong as a model for human language and complex auditory perception. Zebra finches are one of the most widely studied songbird species in this area of investigation. As they produce song syllables in a fixed sequence, it is reasonable to assume that adult zebra finches are also sensitive to the order of syllables within their song; however, results from electrophysiological and behavioral studies provide somewhat mixed evidence on exactly how sensitive zebra finches are to syllable order as compared, say, to syllable structure. Here, we investigate how well adult zebra finches can discriminate changes in syllable order relative to changes in syllable structure in their natural song motifs. In addition, we identify a possible role for experience in enhancing sensitivity to syllable order. We found that both male and female adult zebra finches are surprisingly poor at discriminating changes to the order of syllables within their species-specific song motifs, but are extraordinarily good at discriminating changes to syllable structure (i.e., reversals) in specific syllables. Direct experience or familiarity with a song, either using the bird’s own song (BOS) or the song of a flock mate as the test stimulus, improved both male and female zebra finches’ sensitivity to syllable order. However, even with experience, birds remained much more sensitive to structural changes in syllables. These results help to clarify some of the ambiguities from the literature on the discriminability of changes in syllable order in zebra finches, provide potential insight on the ethological significance of zebra finch song features, and suggest new avenues of investigation in using zebra finches as animal models for sequential sound processing.     

Masked syllable priming of English nouns.

This study investigates the role of sublexical units in the phonological encoding of English single-word production in a word-naming task (Experiment 1) and a picture-naming task (Experiment 2). Targets corresponded to bisyllabic English nouns with word-initial stress which varied on the structure of their first syllable: CV (e.g., pi.lot), CVC (e.g., pic.nic), or CV[C] (e. g., pi[ll]ow).1 Targets were preceded by a visually masked prime that either matched their first syllable (e.g., pi%%% - pi.lot) or that was one segment longer (e.g., pil%% - pi.lot) or shorter (e.g., pi%%%% - pic.nic) than the first syllable. Response times were compared to a neutral control condition (e.g., %&$%% - pi.lot) to measure the priming effects (either facilitation or inhibition). Results showed significant facilitation for both the CV and the CVC conditions. However, contrary to previous findings, there was no interaction between the syllabic structure of the prime and the target.     

The relation between discriminability and memory for vowels,consonants, and silent-center vowels

People remember lists of vowel-contrasting syllables better than lists that vary only in stop consonant identity. Most views suggest that this difference is due to the structure of immediate memory and the greater discriminability of vowels compared with consonants. In all of these views, there is a presumed systematic relationship between discriminability and recall so that the more discriminable an item, the better that item should be recalled. The 11 experiments reported here measured the relative discriminability of and compared serial recall for (1) intact syllables that varied only in the medial vowel, (2) intact syllables that varied only in the initial consonant, and (3) syllables with the center vowel replaced by silence (so-called silent-center vowels). When item discriminability, as measured by identification, was equated for consonant-contrasting and silent-center lists, serial recall performance was also equal. However, even when the vowels were less discriminable than the consonants or silentcenter vowels, serial recall performance for the vowels was still better. These results are problematic for theories based on acoustic discriminability but can be explained parsimoniously by Nairne’s (1990) feature model.     

Laterality effects in the processing of syllable structure.

Recent phonological research has shown that the syllable plays a major role in the phonology of German. The present study investigates laterality effects in the processing of syllable structure by means of dichotic presentation of German word pairs that differ in number of syllables, but that differ minimally in the phonemes they comprise (e.g., BREIT and BEREIT). Results showed a sex difference in laterality for the processing of the experimental stimuli, with a greater right-hemispheric lateralization in men and a more bilateral organization in women.