Integration of local features as a function of global goodness and spacing

In two experiments, the accuracy with which subjects detected a conjunction of features was examined as a function of the spacing between items and the goodness of the axis along which they were located. In each array, two items were arranged along a vertical, a horizontal, or a diagonal axis. Based on the well-established oblique effect, the vertical and horizontal axes were considered to be good global patterns and the diagonals were considered to be poor. In Experiment 1, the two items in an array could be two horizontal lines, two vertical lines, a vertical and a horizontal line, or a plus sign with one of the single lines. In Experiment 2, a positive- and a negative-diagonal line were used as the individual features, and an "X" was used as the conjunction. The results from Experiment 1 indicated that global goodness influenced only the rate of illusory conjunctions, and not of feature errors. Illusory conjunctions of vertical and horizontal line segments were more likely to occur in vertical and horizontal arrangements. The results from Experiment 2 revealed a reversal of the effect of global goodness on the rate of illusory conjunctions: Illusory conjunctions of negative- and positive-diagonal line segments were more likely to occur in diagonal arrangements. The results of both experiments taken together showed the existence of an important and new factor that influences the likelihood that features of shape will be conjoined: the ease with which line segments conjoin when they are translated along their extent toward each other. In both experiments, greater spacing between items produced more feature-identification errors and fewer feature-integration errors than did less spacing.     

The role of attention in illusory conjunctions

In five experiments, we investigated the effects of attention on illusory conjunctions formed between features of unrelated objects. The first three experiments used a weak manipulation of attention and found that illusory conjunctions formed either among features receiving high attentional priority or among features receiving low attentional priority were not more frequent than were conjunctions formed between mixed features of different attentional priority. The last two experiments used a strong manipulation of attention and failed to reveal any evidence of true illusory conjunctions. The results are inconsistent with the feature-integration theory, which predicts that when attention is focused on a subset of items, illusory conjunctions ought to occur within and outside of the attended subset, but not between the attended and unattended items.     

注意在视觉特征捆绑中的作用

通过两项视觉特征捆绑实验,探讨注意的作用及机制。实验1采用双任务范式,考察不同注意分散水平下的错觉性结合(IC)差异。实验2采用空间提示范式,考察集中注意和分散注意条件下的IC差异。两个实验结果都表明,注意在视觉特征捆绑中起重要作用,集中注意能有效地减少IC的出现。同时,注意对特征捆绑的调节作用表现出距离效应,即近距离比远距离的IC错误多,提示注意的作用机制可能与空间距离信息有关。     

Repetition blindness and illusory conjunctions: errors in binding visual types with visual tokens.

Repetition blindness (Kanwisher, 1986, 1987) has been defined as the failure to detect or recall repetitions of words presented in rapid serial visual presentation (RSVP). The experiments presented here suggest that repetition blindness (RB) is a more general visual phenomenon, and examine its relationship to feature integration theory (Treisman & Gelade, 1980). Experiment 1 shows RB for letters distributed through space, time, or both. Experiment 2 demonstrates RB for repeated colors in RSVP lists. In Experiments 3 and 4, RB was found for repeated letters and colors in spatial arrays. Experiment 5 provides evidence that the mental representations of discrete objects (called "visual tokens" here) that are necessary to detect visual repetitions (Kanwisher, 1987) are the same as the "object files" (Kahneman & Treisman, 1984) in which visual features are conjoined. In Experiment 6, repetition blindness for the second occurrence of a repeated letter resulted only when the first occurrence was attended to. The overall results suggest that a general dissociation between types and tokens in visual information processing can account for both repetition blindness and illusory conjunctions.     

Illusory Conjunctions of Color and Motion With Shape Following Bilateral Parietal Lesions

The primate visual system responds to shapes, colors, and various other features more strongly in some brain areas than others. However, it remains unclear how these features are bound together so that an object with all its attributes is perceived. A patient (R.M.) with bilateral parietal-occipital lesions has been shown previously to miscombine the shape and color of items, making errors known as illusory conjunctions (ICs). In this study, we examined the effects of a third feature (motion) on this patient's IC rates. R.M. was presented with two letters that moved in different ways. He often reported seeing the shape of one of the letters with the other letter's motion. His performance on the same task with three features shows that correctly combining two features did not necessarily lead to correctly binding the third. These data support modularity of feature representations in the human brain and provide supporting evidence that spatial representations associated with the parietal lobe are necessary for normal feature integration.     

Illusory conjunctions inside and outside the focus of attention

This article addresses 2 questions that arise from the finding that visual scenes are first parsed into visual features: (a) the accumulation of location information about objects during their recognition and (b) the mechanism for the binding of the visual features. The first 2 experiments demonstrated that when 2 colored letters were presented outside the initial focus of attention, illusory conjunctions between the color of one letter and the shape of the other were formed only if the letters were less than 1 degree apart. Separation greater than 2 degrees resulted in fewer conjunction errors than expected by chance. Experiments 3 and 4 showed that inside the spread of attention, illusory conjunctions between the 2 letters can occur regardless of the distance between them. In addition, these experiments demonstrated that the span of attention can expand or shrink like a spotlight. The results suggest that features inside the focus of attention are integrated by an expandable focal attention mechanism that conjoins all features that appear inside its focus. Visual features outside the focus of attention may be registered with coarse location information prior to their integration. Alternatively, a quick and imprecise shift of attention to the periphery may lead to illusory conjunctions among adjacent stimuli.     

When do letter features migrate? A boundary condition for feature-integration theory

Feature-integration theory postulates that a lapse of attention will allow letter features to change position and to recombine as illusory conjunctions (Treisman & Paterson, 1984). To study such errors, we used a set of uppercase letters known to yield illusory conjunctions in each of three tasks. The first, a bar-probe task, showed whole-character mislocations but not errors based on feature migration and recombination. The second, a two-alternative forced-choice detection task, allowed subjects to focus on the presence or absence of subletter features and showed illusory conjunctions based on feature migration and recombination. The third was also a two-alternative forced-choice detection task, but we manipulated the subjects' knowledge of the shape of the stimuli: In the case-certain condition, the stimuli were always in uppercase, but in the case-uncertain condition, the stimuli could appear in either upper- or lowercase. Subjects in the case-certain condition produced illusory conjunctions based on feature recombination, whereas subjects in the case-uncertain condition did not. The results suggest that when subjects can view the stimuli as feature groups, letter features regroup as illusory conjunctions; when subjects encode the stimuli as letters, whole items may be mislocated, but subletter features are not. Thus, illusory conjunctions reflect the subject's processing strategy, rather than the architecture of the visual system.     

Illusory conjunctions reflect the time course of the attentional blink

Illusory conjunctions in the time domain are binding errors for features from stimuli presented sequentially but in the same spatial position. A similar experimental paradigm is employed for the attentional blink (AB), an impairment of performance for the second of two targets when it is presented 200–500 msec after the first target. The analysis of errors along the time course of the AB allows the testing of models of illusory conjunctions. In an experiment, observers identified one (control condition) or two (experimental condition) letters in a specified color, so that illusory conjunctions in each response could be linked to specific positions in the series. Two items in the target colors (red and white, embedded in distractors of different colors) were employed in four conditions defined according to whether both targets were in the same or different colors. Besides the U-shaped function for hits, the errors were analyzed by calculating several response parameters reflecting characteristics such as the average position of the responses or the attentional suppression during the blink. The several error parameters cluster in two time courses, as would be expected from prevailing models of the AB. Furthermore, the results match the predictions from Botella, Barriopedro, and Suero’s (Journal of Experimental Psychology: Human Perception and Performance, 27, 1452–1467, 2001) model for illusory conjunctions.     

Illusory conjunctions in the perception of objects

In perceiving objects we may synthesize conjunctions of separable features by directing attention serially to each item in turn (A. Treisman and G. Gelade, Cognitive Psychology, 1980, 12, 97–136). This feature-integration theory predicts that when attention is diverted or overloaded, features may be wrongly recombined, giving rise to “illusory conjunctions.” The present paper confirms that illusory conjunctions are frequently experienced among unattended stimuli varying in color and shape, and that they occur also with size and solidity (outlined versus filled-in shapes). They are shown both in verbal recall and in simultaneous and successive matching tasks, making it unlikely that they depend on verbal labeling or on memory failure. They occur as often between stimuli differing on many features as between more similar stimuli, and spatial separation has little effect on their frequency. Each feature seems to be coded as an independent entity and to migrate, when attention is diverted, with few constraints from the other features of its source or destination.     

Dissimilar items benefit from phonological similarity in serial recall

In short-term serial recall, similar sounding items are remembered less well than items that do not sound alike. This phonological similarity effect has been observed with lists composed only of similar items, and also with lists that mix together similar and dissimilar items. An additional consistent finding has been what the authors call dissimilar immunity, the finding that ordered recall of dissimilar items is the same whether these items occur in pure dissimilar or mixed lists. The authors present 3 experiments that disconfirm these previous findings by showing that dissimilar items on mixed lists are recalled better than their counterparts on pure lists if order errors are considered separately from intrusion errors (Experiment 1), or if intrusion errors are experimentally controlled (Experiments 2 and 3). The memory benefit for dissimilar items on mixed lists poses a challenge for current models of short-term serial recall.     

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short-term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC-trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.     

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short‐term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC‐trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.     

Feature binding across different visual dimensions

The human brain represents different kinds of visual feature dimensions in different ways. For example, surface features exhibit some properties that are very different from contour features, and some feature dimensions may be represented more extensively in either the dorsal or the ventral visual stream. Given such differences, we investigated feature binding across different feature dimensions and whether some feature dimensions might be more easily bound together than others. In Experiment 1, we looked at cross-dimension bindings for all combinations of color, orientation, and shape dimensions, while at the same time controlling for feature discriminability. Rates of correct binding, illusory conjunctions, and feature errors were equivalent in all cases. There was no bias so that some feature dimensions were easier to combine than others. In Experiment 2, we manipulated the difficulty of feature discrimination for the key, target-defining feature and the report feature. Rates of binding errors increased with difficulty of the key feature, but not with that of the report feature. The accuracy of feature discrimination could be dissociated from the accuracy of binding the feature to an object. Across both experiments, the accuracy of feature binding was independent of specific feature dimensions or perceptibility. These findings are discussed in relation to both feature integration and multiple-stage accounts of visual feature integration.     

Does maintaining bindings in visual working memory require more attention than maintaining features?

ABSTRACT

Whether more attention is required for maintaining bindings than maintaining features in visual working memory (VWM) remains an open question. If maintaining bindings in VWM does not require more attention than maintaining features, is it related to the stability of binding representations? In this study, we explored whether maintaining bindings requires more attention than maintaining features for similar and dissimilar objects by inserting a feature report task into the maintenance phase of VWM in Experiments 1 and 2. We also investigated whether the effect of similarity on the attentional requirement for maintaining bindings and features is due to the stability of VWM representations by inserting a suffix during the maintenance phase of VWM in Experiment 3. The results showed that when object-based attention was consumed, bindings were more impaired than features for dissimilar objects but not for similar objects. We also found that the bindings of similar objects were less interfered by the suffix than those of dissimilar objects. Our findings suggest that maintaining bindings does not require more attention than maintaining features when the binding representations are stable in VWM and similarity improves the stability of binding representations.     

Guided search: an alternative to the feature integration model for visual search

Subjects searched sets of items for targets defined by conjunctions of color and form, color and orientation, or color and size. Set size was varied and reaction times (RT) were measured. For many unpracticed subjects, the slopes of the resulting RT X Set Size functions are too shallow to be consistent with Treisman's feature integration model, which proposes serial, self-terminating search for conjunctions. Searches for triple conjunctions (Color X Size X Form) are easier than searches for standard conjunctions and can be independent of set size. A guided search model similar to Hoffman's (1979) two-stage model can account for these data. In the model, parallel processes use information about simple features to guide attention in the search for conjunctions. Triple conjunctions are found more efficiently than standard conjunctions because three parallel processes can guide attention more effectively than two.     

视觉特征捆绑的认知机制研究

以大学生为被试,探讨视觉特征捆绑的认知机制。实验采用空间提示范式,要求被试完成字母形状和颜色的辨别任务,考察集中注意和分散注意条件下的IC差异。结果表明,注意在视觉特征捆绑中起重要作用,集中注意能有效地减少IC的出现。同时注意对特征捆绑的调节作用表现出距离效应,即近距离比远距离的IC错误多,提示了注意的作用机制有可能与空间距离信息有关。     

顶叶在特征捆绑中的作用--对一例典型双侧顶叶损伤病人的研究

本实验以一例典型双侧顶叶损伤患者为研究对象,以数字和几何形状为材料,采用形状和颜色特征识别任务,主要考察了顶叶及空间信息是否影响视觉特征捆绑。结果显示,患者在特征捆绑任务上操作成绩较差,错觉性结合错误远远多于特征错误,且正确反应及错觉性结合受刺激间的距离及呈现方式的影响,表现出距离和位置效应。这些结果表明,顶叶在视觉特征捆绑中起重要作用,这种影响作用很可能与空间注意有关。本研究进一步为特征整合理论提供了神经心理学的证据。     

汉语短时序列回忆中的语音相似性和视觉相似性效应

语音相似性效应和视觉相似性效应是短时序列回忆中的两个典型性效应, 但前人很少探讨这两种效应的交互作用。本研究利用汉语字形和语音的属性, 观察汉字短时序列回忆中语音相似性效应、视觉相似性效应及两者的交互作用。研究结果发现当回忆项目在语音或视觉上单纯相似或不相似时, 视觉相似性效应及其与语音相似性的交互作用与混合词表条件下所发现的结果有很大的不同。这个研究结果为丰富和补充相关理论模型提供了进一步实证依据。     

Illusory conjunctions are alive and well: a reply to Donk (1999).

When presented with a red T and a green O, observers occasionally make conjunction responses and indicate that they saw a green T. These errors have been interpreted as reflecting separable processing stages of feature detection and integration with the illusory conjunctions arising from a failure at the integration stage. Recently, M. Donk (1999) asserted that the phenomenon of illusory conjunctions is an artifact. Conjunction reports are actually the result of confusing a nontarget item (O in the example above) for a target item (the letter T) and (correctly) reporting the color associated with the (incorrectly) selected target. The authors demonstrate that although target-nontarget confusion errors are a potential source of conjunction reports, there is a plethora of findings that cannot be accounted for by this confusion model. A review of the literature indicates that in many studies, illusory conjunctions do result from a failure to properly integrate features.     

Causal status as a determinant of feature centrality

One of the major problems in categorization research is the lack of systematic ways of constraining feature weights. We propose one method of operationalizing feature centrality, a causal status hypothesis which states that a cause feature is judged to be more central than its effect feature in categorization. In Experiment 1, participants learned a novel category with three characteristic features that were causally related into a single causal chain and judged the likelihood that new objects belong to the category. Likelihood ratings for items missing the most fundamental cause were lower than those for items missing the intermediate cause, which in turn were lower than those for items missing the terminal effect. The causal status effect was also obtained in goodness-of-exemplar judgments (Experiment 2) and in free-sorting tasks (Experiment 3), but it was weaker in similarity judgments than in categorization judgments (Experiment 4). Experiment 5 shows that the size of the causal status effect is moderated by plausibility of causal relations, and Experiment 6 shows that effect features can be useful in retrieving information about unknown causes. We discuss the scope of the causal status effect and its implications for categorization research.