Su-Ling Yeh

Asymmetric cross-modal effects in time perception.

It is common to judge the duration of an audiovisual event, and yet it remains controversial how the judgment of duration is affected by signals from other modalities. We used an oddball paradigm to examine the effect of sound on the judgment of visual duration and that of a visual object on the judgment of an auditory duration. In a series of standards and oddballs, the participants compared the duration of the oddballs to that of the standards. Results showed asymmetric cross-modal effects, supporting the auditory dominance hypothesis: a sound extends the perceived visual duration, whereas a visual object has no effect on perceived auditory duration. The possible mechanisms (pacemaker or mode switch) proposed in the Scalar Expectancy Theory [Gibbon, J., Church, R. M., & Meck, W. H. (1984). Scalar timing in memory. In J. Gibbon & L. Allan (Eds.), Annals of the New York Academy of Sciences: Vol. 423. Timing and time perception (pp. 52-77). New York: New York Academy of Sciences] were examined using different standard durations. We conclude that sound increases the perceived visual duration by accelerating the pulse rate in the visual pacemaker.

Accessing the meaning of invisible words.

Previous research has shown implicit semantic processing of faces or pictures, but whether symbolic carriers such as words can be processed this way remains controversial. Here we examine this issue by adopting the continuous flash suppression paradigm to ensure that the processing undergone is indeed unconscious without the involvement of partial awareness. Negative or neutral words projected into one eye were made invisible due to strong suppression induced by dynamic-noise patterns shown in the other eye through binocular rivalry. Inverted and scrambled words were used as controls to provide baselines at orthographic and feature levels, respectively. Compared to neutral words, emotion-described and emotion-induced negative words required longer time to release from suppression, but only for upright words. These results suggest that words can be processed unconsciously up to semantic level since under interocular suppression completely invisible words can lead to different processing speed due to the emotion information they carry.

A common mechanism for perceptual filling-in and motion-induced blindness ☆

Perceptual-filling-in (PFI) and motion-induced-blindness (MIB) are two phenomena of temporary blindness in which, after prolonged viewing, perceptually salient targets repeatedly disappear and reappear, amidst a field of distracters (i.e., non-targets). Past studies have shown that boundary adaptation is important in PFI, and that depth ordering between target and distracter pattern is important in MIB. Here we show that the reverse is also true; that boundary adaptation is important in MIB, and that depth ordering is important in PFI. Results corroborate our earlier conjecture that PFI and MIB are highly related phenomena that share a common underlying mechanism. We argue that this mechanism involves boundary adaptation, but also that the depth effect shows that boundary adaptation can be no more than a sufficient cause of PFI and MIB, and not a necessary one.

Crossmodal constraints on human perceptual awareness: auditory semantic modulation of binocular rivalry.

We report a series of experiments utilizing the binocular rivalry paradigm designed to investigate whether auditory semantic context modulates visual awareness. Binocular rivalry refers to the phenomenon whereby when two different figures are presented to each eye, observers perceive each figure as being dominant in alternation over time. The results demonstrate that participants report a particular percept as being dominant for less of the time when listening to an auditory soundtrack that happens to be semantically congruent with the other alternative (i.e., the competing) percept, as compared to when listening to an auditory soundtrack that was irrelevant to both visual figures (Experiment 1A). When a visually presented word was provided as a semantic cue, no such semantic modulatory effect was observed (Experiment 1B). We also demonstrate that the crossmodal semantic modulation of binocular rivalry was robustly observed irrespective of participants’ attentional control over the dichoptic figures and the relative luminance contrast between the figures (Experiments 2A and 2B). The pattern of crossmodal semantic effects reported here cannot simply be attributed to the meaning of the soundtrack guiding participants’ attention or biasing their behavioral responses. Hence, these results support the claim that crossmodal perceptual information can serve as a constraint on human visual awareness in terms of their semantic congruency.

Semantic Priming From Crowded Words

Vision in a cluttered scene is extremely inefficient. This damaging effect of clutter, known as crowding, affects many aspects of visual processing (e.g., reading speed). We examined observers’ processing of crowded targets in a lexical decision task, using single-character Chinese words that are compact but carry semantic meaning. Despite being unrecognizable and indistinguishable from matched nonwords, crowded prime words still generated robust semantic-priming effects on lexical decisions for test words presented in isolation. Indeed, the semantic-priming effect of crowded primes was similar to that of uncrowded primes. These findings show that the meanings of words survive crowding even when the identities of the words do not, suggesting that crowding does not prevent semantic activation, a process that may have evolved in the context of a cluttered visual environment.

The role of learning experience on the perceptual organization of Chinese characters

The effect of learning experience on the perceived graphemic similarity of Chinese characters was examined by comparing results of the constrained (Experiment 1) and unconstrained (Experiment 2) shape-sorting tasks obtained from various groups of participants with different learning experiences and ages. The results from hierarchical cluster analysis showed that both Taiwanese and Japanese undergraduates classified characters in relation to their configurational structures, whereas American undergraduates, Taiwanese illiterate adults, and kindergartners categorized characters based on strokes or components. Although a trend of developmental changes from local details to more globally defined patterns was found, the identification of structure as consistently perceived by skilled readers has to be nourished by learning experience and cannot be obtained solely through maturation.

Learning-Based Prediction of Visual Attention for Video Signals

Visual attention, which is an important characteristic of human visual system, is a useful clue for image processing and compression applications in the real world. This paper proposes a computational scheme that adopts both low-level and high-level features to predict visual attention from video signal by machine learning. The adoption of low-level features (color, orientation, and motion) is based on the study of visual cells, and the adoption of the human face as a high-level feature is based on the study of media communications. We show that such a scheme is more robust than those using purely single low- or high-level features. Unlike conventional techniques, our scheme is able to learn the relationship between features and visual attention to avoid perceptual mismatch between the estimated salience and the actual human fixation. We also show that selecting the representative training samples according to the fixation distribution improves the efficacy of regressive training. Experimental results are shown to demonstrate the advantages of the proposed scheme.

FIGURAL AFTEREFFECTS AND SPATIAL ATTENTION

Distracting attention away from the location of an adaptation figure reduces the positional shift of a displaced test figure in the figural aftereffect (FAE). Participants performed an alignment task after adaptation involving various manipulations of spatial attention. In 1 condition, participants counted how often numbers occurred in an alphanumeric sequence presented during adaptation. (The sequence also appeared in a comparison condition, but no attention was required.) The FAE was reduced when the alphanumeric sequence attended to was in the center of the display while the adaptation figure was 3 degrees eccentric but not when the pattern was superimposed on the adaptation figure. Forced attention to 1 feature of the adaptation figure, its orientation, did not reduce the FAE (Experiment 3). To obtain a maximum FAE, the span of attention must cover the adaptation figure.

Sublexical processing in visual recognition of Chinese characters: evidence from repetition blindness for subcharacter components.

Repetition blindness (RB) refers to the failure to detect the second occurrence of a repeated item in rapid serial visual presentation (RSVP). In two experiments using RSVP, the ability to report two critical characters was found to be impaired when these two characters were identical (Experiment 1) or similar by sharing one repeated component (Experiment 2), as opposed to when they were different characters with no common components. RB for the whole character occurred when the exposure duration was more than 50 ms with one intervening character between the two critical characters (lag=1), whereas RB for subcharacter components was more evident at exposure durations shorter than 50 ms with no intervening character (lag=0). These results provide support for the model of sublexical processing in Chinese character recognition.

Object-based attention occurs regardless of object awareness

In this study, we investigated whether awareness of objects is necessary for object-based guidance of attention. We used the two-rectangle method (Egly, Driver, & Rafal, 1994) to probe object-based attention and adopted the continuous flash suppression technique (Tsuchiya & Koch, 2005) to control for the visibility of the two rectangles. Our results show that object-based attention, as indexed by the same-object advantage—faster response to a target within a cued object than within a noncued object—was obtained regardless of participants’ awareness of the objects. This study provides the first evidence of object-based attention under unconscious conditions by showing that the selection unit of attention can be at an object level even when these objects are invisible—a level higher than the previous evidence for a subliminally cued location. We suggest that object-based attentional guidance plays a fundamental role of binding features in both the conscious and unconscious mind.