Selecting spatial frames of reference for visual target localization

This study examined the selection of spatial frames of reference for target localization in visual search. Participants searched for local target characters in global character configurations. The local targets could be localized relative to the character configuration in which they were embedded or relative to the presentation screen on which the configurations were displayed. We investigated under which conditions the configurations, or the screen served as frame of reference for target localization. Three experiments revealed an increasing impact of screen-related target localization with decreasing spatial uncertainty of targets in screen-related coordinates. The results indicate the capability of the visual system to localize relevant visual stimuli with respect to those frames of reference that yield the most redundant spatial distribution of these stimuli.     

Electrocutaneous stimulation II. The estimation of distance between two points

Using a numerical estimation procedure, subjects judged the perceived distance between pairs of brief electrical stimuli presented over different physical distances, on different body regions, and in different spatial orientations. The skin turns out to be anisotropic, with the same physical separation between electrodes appearing greater on the forehead than on the forearm, greater on the forearm than on the abdomen. Perceived distance also depends on the orientation and, to some extent, on the time relation between the two electrical pulses. Under all conditions, the perceived distance between electrical stimuli was “compressed” as compared with visual distance. These results bear on the design of devices that attempt to transmit information by electrical stimulation of the skin.     

Target detection and localization in visual search: a dual systems perspective

The dual visual systems framework (Milner & Goodale, 1995) was used to explore target detection and localization in visual search. Observers searched for a small patch of tilted bars against a dense background of upright bars. Target detection was performed along with two different localization tasks: direct pointing, designed to engage the dorsal stream, and indirect pointing, designed to engage the ventral stream. The results indicated that (1) target detection was influenced more by orientation differences in 3-D space than by 2-D pictorial differences, (2) target localization was more accurate for direct than for indirect pointing, and (3) there were performance costs for indirect localization when it followed target detection, but not for direct localization. This is consistent with direct localization's having greater dependence on the dorsal visual system than either target detection or indirect localization.     

两种参照作用下的视觉定位

本实验采用多点视觉定位作业,研究视觉定位中的两种参照对定位成绩的影响。实验采用一些附加线条与三个刺激形成有特征的刺激图和无特征的刺激图,并与没有附加线条的情况进行了比较。有特征的刺激图是指这些附加的线条与刺激点构成一定的特征,如一个字母或图形等;无特征的刺激图指刺激点不能与附加线条构成有规律的特征。结果发现,当有附加线条的图形呈现时,被试的定位误差大于控制组,表现出一级参照对视觉定位的干扰作用,而且在呈现时间为100ms、200ms、300ms时,都是如此。在有特征组内,不同的特征对定位精确性的影响依赖于时间因素。     

Effects of tilted orientations and face-like configurations on visual search asymmetry in macaques

Visual search asymmetry has been used as an important tool for exploring cognitive mechanisms in humans. Here, we examined visual search asymmetry in two macaques toward two types of stimulus: the orientation of line stimuli and face-like stimuli. In the experiment, the monkeys were required to detect an odd target among numerous uniform distracters. The monkeys detected a tilted-lines target among horizontal- or vertical-lined distracters significantly faster than a horizontal- or vertical-lined target among tilted-lined distracters, regardless of the display size. However, unlike the situation in which inverted-face stimuli were introduced as distracters, this effect was diminished if upright-face stimuli were used as distracters. Additionally, monkeys detected an upright-face target among inverted-face distracters significantly faster than an inverted-face target among upright-face distracters, regardless of the display size. These results demonstrate that macaques can search a target efficiently to detect both tilted lines among non-tilted lines and upright faces among inverted faces. This clarifies that there are several types of visual search asymmetry in macaques.     

Vibrotactile localization on the arm: effects of place, space, and age

Although tactile acuity has been explored for touch stimuli, vibrotactile resolution on the skin has not. In the present experiments, we explored the ability to localize vibrotactile stimuli on a linear array of tactors on the forearm. We examined the influence of a number of stimulus parameters, including the frequency of the vibratory stimulus, the locations of the stimulus sites on the body relative to specific body references or landmarks, the proximity among driven loci, and the age of the observer. Stimulus frequency and age group showed much less of an effect on localization than was expected. The position of stimulus sites relative to body landmarks and the separation among sites exerted the strongest influence on localization accuracy, and these effects could be mimicked by introducing an "artificial" referent into the tactile array.     

奖惩线索条件下内外倾个体的自主唤醒和行为反应

将停止信号任务和金钱激励延迟任务相结合,使用16导生理记录仪记录被试的生理指标,探讨内外倾者在动机凸显情景下的生理唤醒特点以及反应调节能力。结果发现,隐含奖励和惩罚线索呈现之后,内外倾者的心率增快,内倾者的皮肤电活动显著增强。在停止信号任务中的优势反应阶段,内外倾者表现为对奖励凸显线索刺激的反应时缩短;而在非优势反应阶段,和外倾者相比较,内倾者的抑制反应错误率增高。表明内外倾者在奖惩线索条件下表现出不同的生理唤醒特点和行为反应。     

Oculomanual Coordination in Tracking of Pseudorandom Target Motion Stimuli

Oculomanual coordination was investigated in 9 healthy subjects during tracking of pseudorandom motion stimuli. Each subject was required to track visual stimuli under eye-hand (EH) and eye-alone (EA) conditions. Subjects were exposed to 3 types of mixed sinusoidal stimulus with varying frequency or amplitude of the highest frequency component, or various degrees of irregularity. Progressive degradation in tracking performance was nonlinearly induced by an increase in either (a) the highest frequency component or (b) its amplitude, but not by stimulus irregularity. No significant difference was found in eye velocity gain and phase under the EH and EA conditions. Eye and hand responses were found to be highly correlated in gain and phase when compared across frequencies and motion stimuli. The results suggest that frequency and amplitude are dominant factors controlling the breakdown of oculomanual performance in response to pseudorandom stimuli. Frequency responses of smooth pursuit eye movements are not affected by the hand motion in pursuit of unpredictable stimuli. Eye and hand motor systems appear to share common nonlinear drive mechanisms when pursuing pseudorandom target motion stimuli.     

Divided attention enhances the recognition of emotional stimuli: evidence from the attentional boost effect

The present study examined predictions of the early-phase-elevated-attention hypothesis of the attentional boost effect (ABE), which suggests that transient increases in attention at encoding, as instantiated in the ABE paradigm, should enhance the recognition of neutral and positive items (whose encoding is mostly based on controlled processes), while having small or null effects on the recognition of negative items (whose encoding is primarily based on automatic processes). Participants were presented a sequence of negative, neutral and positive stimuli (pictures in Experiment 1, words in Experiment 2) associated to target (red) squares, distractor (green) squares or no squares (baseline condition). They were told to attend to the pictures/words and simultaneously press the spacebar of the computer when a red square appeared. In a later recognition task, stimuli associated to target squares were recognised better than stimuli associated to distractor squares, replicating the standard ABE. More importantly, we also found that: (a) the memory enhancement following target detection occurred with all types of stimuli (neutral, negative and positive) and (b) the advantage of negative stimuli over neutral stimuli was intact in the DA condition. These findings suggest that the encoding of negative stimuli depends on both controlled (attention-dependent) and automatic (attention-independent) processes.     

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.     

Tagging multiple emotional stimuli: negative valence has little benefit

Six experiments examined the influence of emotional valence on the tagging and enumeration of multiple targets. Experiments 1, 5 and 6 found that there was no difference in the efficiency of tagging/enumerating multiple negative or positive stimuli. Experiment 2 showed that, when neutral-expression face distractors were present, enumerating negative targets was faster overall, but was only more efficient for small numbers of targets. Experiments 3 and 4 determined that this negative target advantage was most likely caused by increased attentional guidance to negatively-valenced stimuli and was not based on simple visual feature differences. The findings suggest that a multiple-target negative stimulus advantage will only occur under conditions of attentional competition, and for relatively small numbers of targets. The results are discussed in relation to theories of multiple- and single-item processing, threat-priority mechanisms, and the types of representations that support different attentional tasks.     

Perception of emergent configurations in humans (Homo sapiens) and chimpanzees (Pan troglodytes)

We examined the perceptions of emergent configurations in humans and chimpanzees using a target-localization task. The stimulus display consisted of a target placed among multiple identical distractors. The target and distractors were presented either solely, within congruent contexts in which salient configurations emerge, or within incongruent contexts in which salient configurations do not emerge. We found that congruent contexts had similar facilitative effects on target localization by humans and chimpanzees, whereas similar disruptive effects emerged when the stimuli were presented within incongruent contexts. When display size was manipulated, targets under the congruent-context condition were localized in a parallel manner, but those under the no-context and incongruent-context conditions were localized in a serial manner by both species. These results suggest that both humans and chimpanzees perceive emergent configurations when targets and distractors are presented within certain congruent contexts and that they process such emergent configurations preattentively.     

An event‐related potential study on the “check operation” in the Eriksen task1

Abstract: We examined two issues for the Eriksen task with two types of stimuli, the central target letter of which was flanked with noise (e.g., HHHHH for compatible stimuli and SSHSS for incompatible stimuli). First, we examined whether or not a response‐stop function is carried out until the check operation to detect and correct erroneous response readiness has finished (Eriksen & Eriksen, 1974). Second, reaction times for incompatible stimuli are not prolonged if only identical noise stimuli are used throughout the block. This phenomenon is called the blocking effect. We then explored whether or not the blocking effect can be caused by the selective inhibition of erroneous response readiness (Eriksen & Schultz, 1979). Sixteen participants (18–29 years old) selectively pressed one of two buttons for the target letter. The results showed that the negative potential related to the response‐stop function was enlarged for incompatible stimuli. Moreover, the blocking effect was observed, while erroneous response readiness was still observable for incompatible stimuli. These results suggest that the blocking effect is caused by something other than reciprocal inhibition.     

汉字认知过程中整字对部件的影响

英文研究中,"字优效应"是单词促进字母加工的一个重要依据。但中文研究中还存在一些争议。本研究通过两个实验考查了汉字的部件认知中,汉字整体对局部(部件)的影响。实验刺激材料分为三种,即左右结构或上下结构的真字、假字与部件字。目标部件为既能够放置于三种字符的左侧,又能放置于右侧(上部或下部)的汉字部件。实验一采用Reicher-Wheeler实验任务,先呈现刺激材料350ms,掩蔽后再呈现需要判断的目标部件,被试对目标部件进行按键反应。实验二中采用部件判断实验任务,先呈现需要判断的目标部件,再呈现刺激材料,被试对刺激材料中是否包含目标部件进行按键反应。记录反应时与正确率。27位健康女性大学生参与本实验。结果显示:(1)不论是Reicher-Wheeler实验任务还是部件判断实验任务,均显示部件字的部件认知判断速度最快。真字与假字相比,无"字优效应"。真字与部件字相比,存在着"字劣效应"。这些结果表明,汉字整字对汉字部件认知加工起到抑制作用;(2)两个实验任务均表现出汉字结构方式效应,即对左右结构的汉字的部件认知比上下结构的汉字更快;(3)部件的空间位置对部件识别存在影响。实验一中对下部件分辨最困难,分辨时间最长;实验二中发现对左部件的反应最快。字符结构方式效应与部件空间位置效应既存在于真字中,也存在于假字中。     

Age-Invariance in the Asymmetry of Stimulus-Evoked Emotional Facial Muscle Activity

This study examined possible effects of aging on the lateralization of stimulus-evoked emotional facial muscle activity. Older participants (mean age 68.4 years) and younger participants (mean age 26.4 years) viewed slides of positive, neutral, or negative emotional content. While participants viewed the slides, bilateral electromyographic (EMG) recordings were obtained from the skin surface over zygomatic and corrugator facial muscles. The participants also made ratings of experienced emotional valence and arousal. Expected patterns of subjective experience and asymmetrical EMG activity were found in response to target stimuli. Greater corrugator muscle activity occurred during presentation of negative stimuli, whereas greater zygomatic muscle activity occurred during presentation of positive stimuli. Consistent with right-hemisphere specialization theories of emotion, left-sided facial EMG activity was consistently greater than that of the right side during presentation of emotional stimuli. However, neither subjective ratings nor EMG patterns showed a significant effect of age group. Such similar patterns of emotional response for the two groups suggest, that the aging process does not produce marked changes in stimulus-evoked emotional experience or in the pattern, magnitude, or lateralization of facial muscle activity associated with emotional states.     

Head-centred meridian effect on auditory spatial attention orienting

Six experiments examined the issue of whether one single system or separate systems underlie visual and auditory orienting of spatial attention. When auditory targets were used, reaction times were slower on trials in which cued and target locations were at opposite sides of the vertical head-centred meridian than on trials in which cued and target locations were at opposite sides of the vertical visual meridian or were not separated by any meridian. The head-centred meridian effect for auditory stimuli was apparent when targets were cued by either visual (Experiments 2, 3, and 6) or auditory cues (Experiment 5). Also, the head-centred meridian effect was found when targets were delivered either through headphones (Experiments 2, 3, and 5) or external loudspeakers (Experiment 6). Conversely, participants showed a visual meridian effect when they were required to respond to visual targets (Experiment 4). These results strongly suggest that auditory and visual spatial attention systems are indeed separate, as far as endogenous orienting is concerned.     

Vibrotactile letter recognition: The effects of a ma king stimulus

A series of experiments examined the effect of masking stimuli on the ability of observers to recognize letters of the alphabet through their fingertips. The letters were generated on the 6 × 24 vibrotactile array of the Optacon, a reading aid for the blind. Letter recognition was interfered with by the presence of masking stimuli occurring at the same site on the skin either before (forward masking) or after (backward masking) the target letter had been presented. In general, backward masking interfered with letter recognition more than did forward masking. Backward masking was particularly effective for letters in which the information critical for identification is located on the right side of the letter. Presenting the letters reversed resulted in more forward masking for those letters with critical information now located on the left side. Increasing the time between the target letter and the masking stimuli resulted in improved letter recognition. The implications of the results for tactile reading are discussed.     

Persistence of negative priming: II. Evidence for episodic trace retrieval.

Responses to recently ignored stimuli may be slower or less accurate than to new stimuli. This negative priming effect decays over time when delay is randomized within subjects, but not when delay varies between subjects. In Experiment 1, response-stimulus intervals (RSI) of 500 and 4,000 ms were randomized within subjects in a target localization task. Negative priming of ignored locations diminished with longer delay. However, no significant decay was obtained when RSI and the preceding RSI were equal. Similar results were obtained when RSI and preceding RSI were deliberately confounded by blocking (Experiment 2). Negative priming appears to depend on temporal discriminability of the priming episode.     

Multiple timing and the allocation of attention

Two experiments were designed to examine the effects of multiple timing tasks on prospective time judgment performance. In experiment 1, subjects were required to monitor the durations of one, two, three, or four concurrent target stimuli which began and ended at different times, and then reproduce one of those durations subsequently chosen at random. Time judgment accuracy deteriorated as the number of target stimuli increased. In experiment 2, subjects used the production method to generate specified durations for one, two, three, or four partially overlapping stimuli. Timing was less accurate in conditions involving more target stimuli. In the multiple-target conditions, time judgments were less accurate for the later- rather than earlier-onset targets. The results support an attentional model of timing, and suggest that timing is an effortful process which draws from limited attentional resources.     

Can certain stimulus characteristics influence the hemispheric differences in global and local processing?

Hemispheric processing of global and local form was examined in two experiments in which the size of hierarchical visual stimuli was manipulated in divided-attention tasks. In experiment 1, the subjects were instructed to decide whether or not a symmetrical target (T) was in the visual object presented. In experiment 2, the target to be detected was nonsymmetrical (L). In both studies, global precedence was found depending on stimulus size. When the stimuli subtended about 3 degrees vertically, global dominance was found, but it was not detected when the stimuli subtended about 10 degrees. Experiments 1 and 2 provided evidence against the analytic/holistic dichotomy, presenting the same performance for both hemispheres: the global analysis was much better than the local analysis. When the target was in the global form, both the LH and the RH analyzed the 3 degrees stimuli more efficiently, while both analyzed the 10 degrees stimuli with greater efficiency when the target was in the local form.