Processes of similarity judgment

Similarity underlies fundamental cognitive capabilities such as memory, categorization, decision making, problem solving, and reasoning. Although recent approaches to similarity appreciate the structure of mental representations, they differ in the processes posited to operate over these representations. We present an experiment that differentiates among extant structural accounts of similarity in their ability to account for patterns of similarity ratings. These data pose a challenge for transformation-based models and all but one mapping-based model, the Similarity as Interactive Activation and Mapping (SIAM) model of similarity.     

Dissociating size representation for action and for conscious judgment: Grasping visual illusions without apparent obstacles

Visual illusions provide important evidence for the co-existence of unconscious and conscious representations. Objects surrounded by other figures (e.g., a disc surrounded by smaller or larger rings, Ebbinghaus/Titchener illusion) are consciously perceived as different in size, while the visuo-motor system supposedly uses an unconscious representation of the discs' true size for grip size scaling. Recent evidence suggests other factors than represented size, e.g., surrounding rings conceived as obstacles, affect grip size. Use of the diagonal illusion avoids visual obstacles in the path of the reaching hand. Results support the dual representation theory. Grip size scaling follows actual size independent of illusory effects, which clearly bias conscious perception in direct comparisons of lengths (Experiment 1) and in finger-thumb span indications of perceived length (Experiment 2).     

Comparison of two models of similarity judgment

The conventional multidimensional distance model of similarity judgment was compared with a new model in which component differences are weighted and then averaged. To evaluate the models, qualitative and quantitative predictions were derived from Romney and D'Andrade's (1964) componential analysis of American kinship terms, and these predictions were tested by having subjects rate the similarity (in experiment 1) and the difference (in experiment 2) between all possible pairs of 12 kinship terms. In both experiments, violations of qualitative predictions for both a simple distance model and a simple averaging model revealed that the componential analysis was not sufficient to account for the data. However the averaging model was able to account for the data when the dichotomous dimension of lineality used by Romney and D'Andrade was replaced by a continuous dimension of immediacy or closeness of kin. In contrast, no comparable elaboration under the distance model was successful. These results were discussed in terms of the likely psychological processes underlying similarity judgment.     

Brain activity for visual judgment of lifted weight

It is well established that humans can recognize high-level aspects from point-light biological motion, such as gender and mood. If the task is to judge the manipulated weight we expected that sensorimotor regions should be recruited in the brain. Moreover, we have recently shown that chronic pain in a limb that is involved in the presented movement disturbs the weight judgment. We therefore hypothesized that some cortical regions usually activated during the processing of pain will also be activated while viewing point-light biological motion with the instruction to judge the manipulated weights. We investigated point-light biological motion of two types of movements performed with different weights in a blocked fMRI experiment in healthy subjects. In line with our a priori hypothesis, we found strong activity in the regions known as the neuromatrix of pain, such as the anterior cingulate (ACC), insula, as well as primary and secondary somatosensory regions. We also found activation in the occipital and temporal regions that are typical for biological motion, as well as regions in the cerebellum and prefrontal cortex. The activation of the somatosensory regions probably serves the judgment of the biological motion stimuli. Activation of the anterior cingulate and the insula might be explained by their role in the integration of behaviorally relevant information. Alternatively, these structures are known to be involved in the processing of nociceptive information and pain. So it seems possible that the interference between judgment of weights and perception of pain in chronic pain patients occurs in the somatosensory areas, anterior cingulate and/or insula. This finding provides important information as to the underlying mechanisms used for the weight judgment task, but also why chronic pain interferes with this task.     

Similarity as threat: A motivational explanation of self–other similarity judgment asymmetry

People tend to judge others to be more similar to themselves than themselves are to others. This self–other similarity judgment asymmetry was often explained by a cognitive model. However, some findings were inconsistent with this model, implying that there might be complementary processes underlying such asymmetry. Although a motivational explanation has been proposed to account for the asymmetry, little evidence has been accumulated to verify this explanation and differentiate it from the cognitive model. The current research tested both the core assumption of the motivational explanation as well as a hypothesis derived only from it. Results suggest that the perception of oneself as being similar to others was more threatening to people's uniqueness than the perception of others as being similar to oneself. Individuals with high need for uniqueness exhibited greater asymmetry than did individuals with low need. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural aspects of visual similarity

The hypothesis that visual representations for lines and/or points are independent structural units was tested using similarity judgment and speeded discrimination for pairs of six-segment letter-like figures. The stimuli were constructed such that each of two comparison figures had five segments in common with a standard figure. One figure was similar to the standard in its higher order structure (connectedness and closedness properties), whereas the other differed. The results show that the figures with similar higher order structure were systematically judged more similar to the standard than the figures with different structure. The former were also more difficult to discriminate from standards than the latter, as indicated by both time and error measurements. These effects were less pronounced in sequential than in simultaneous comparisons.     

Studying visual search using systems factorial methodology with target-distractor similarity as the factor

Systems factorial technology (SFT) is a theory-driven set of methodologies oriented toward identification of basic mechanisms, such as parallel versus serial processing, of perception and cognition. Studies employing SFT in visual search with small display sizes have repeatedly shown decisive evidence for parallel processing. The first strong evidence for serial processing was recently found in short-term memory search, using target-distractor (T-D) similarity as a key experimental variable (Townsend & Fifi?, 2004). One of the major goals of the present study was to employ T-D similarity in visual search to learn whether this mode of manipulating processing speed would affect the parallel versus serial issue in that domain. The result was a surprising and regular departure from ordinary parallel or serial processing. The most plausible account at present relies on the notion of positively interacting parallel channels.     

A conjunctive feature similarity effect for visual search

Traditional models of visual search assume interitem similarity effects arise from within each feature dimension independently of other dimensions. In the present study, we examine whether distractor-distractor effects also depend on feature conjunctions (i.e., whether feature conjunctions form a separate “feature” dimension that influences interitem similarity). Spatial frequency and orientation feature dimensions were used to generate distractors. In the bound condition, the number of distractors sharing the same conjunction of features was higher than that in the unbound condition, but the sharing of features within frequency and orientation dimensions was the same across conditions. The results showed that the target was found more efficiently in the bound than in the unbound condition, indicating that distractor-distractor similarity is also influenced by conjunctive representations.     

A conjunctive feature similarity effect for visual search

Traditional models of visual search assume interitem similarity effects arise from within each feature dimension independently of other dimensions. In the present study, we examine whether distractor–distractor effects also depend on feature conjunctions (i.e., whether feature conjunctions form a separate “feature” dimension that influences interitem similarity). Spatial frequency and orientation feature dimensions were used to generate distractors. In the bound condition, the number of distractors sharing the same conjunction of features was higher than that in the unbound condition, but the sharing of features within frequency and orientation dimensions was the same across conditions. The results showed that the target was found more efficiently in the bound than in the unbound condition, indicating that distractor–distractor similarity is also influenced by conjunctive representations.     

Visual similarity is stronger than semantic similarity in guiding visual search for numbers

Using a visual search task, we explored how behavior is influenced by both visual and semantic information. We recorded participants’ eye movements as they searched for a single target number in a search array of single-digit numbers (0–9). We examined the probability of fixating the various distractors as a function of two key dimensions: the visual similarity between the target and each distractor, and the semantic similarity (i.e., the numerical distance) between the target and each distractor. Visual similarity estimates were obtained using multidimensional scaling based on the independent observer similarity ratings. A linear mixed-effects model demonstrated that both visual and semantic similarity influenced the probability that distractors would be fixated. However, the visual similarity effect was substantially larger than the semantic similarity effect. We close by discussing the potential value of using this novel methodological approach and the implications for both simple and complex visual search displays.     

The representation of visual scenes

The visual world exists all around us, yet this information must be gleaned through a succession of eye fixations in which high visual acuity is limited to the small foveal region of each retina. In spite of these physiological constraints, we experience a richly detailed and continuous visual world. Research on transsaccadic memory, perception, picture memory and imagination of scenes will be reviewed. Converging evidence suggests that the representation of visual scenes is much more schematic and abstract than our immediate experience would indicate. The visual system may have evolved to maximize comprehension of discrete views at the expense of representing unnecessary detail, but through the action of attention it allows the viewer to access detail when the need arises. This capability helps to maintain the 'illusion' of seeing a rich and detailed visual world at every glance.     

The effects of visual similarity on proofreading for misspellings

In three experiments, subjects read prose passages and circled misspellings in them. The misspelled words were created by replacing a single letter with another one. The visual similarity between the correct letter and the one that was substituted for it increased the percentage of proofreading errors. The results suggest that proofreaders search through a visual representation of the text and that a hierarchical feature test is applied to this representation, according to which subjects give first priority to resolving letter envelope and second priority to discriminating additional visual features. A sophisticated-guessing decision rule is also implicated for the misspellings that do not alter letter envelope: Subjects are tolerant of missing letter features but are intolerant of additional features.     

Constraining the neural representation of the visual world

Understanding the perception of all but the most impoverished and artificial scenes presents a different and probably far greater challenge from understanding face recognition, reading, or identification (or even categorization) of single objects. Central issues in the interpretation of structured objects and scenes are reviewed, starting with fundamentals such as the meaning of seeing. A theoretical approach to this formidable task is outlined, motivated by some recent developments in neuroscience and neurophilosophy.     

Inaccurate representation of the ground surface beyond a texture boundary

The sequential-surface-integration-process (SSIP) hypothesis was proposed to elucidate how the visual system constructs the ground-surface representation in the intermediate distance range (He et al, 2004 Perception 33 789-806). According to the hypothesis, the SSIP constructs an accurate representation of the near ground surface by using reliable near depth cues. The near ground representation then serves as a template for integrating the adjacent surface patch by using the texture gradient information as the predominant depth cue. By sequentially integrating the surface patches from near to far, the visual system obtains the global ground representation. A critical prediction of the SSIP hypothesis is that, when an abrupt texture-gradient change exists between the near and far ground surfaces, the SSIP can no longer accurately represent the far surface. Consequently, the representation of the far surface will be slanted upward toward the frontoparallel plane (owing to the intrinsic bias of the visual system), and the egocentric distance of a target on the far surface will be underestimated. Our previous findings in the real 3-D environment have shown that observers underestimated the target distance across a texture boundary. Here, we used the virtual-reality system to first test distance judgments with a distance-matching task. We created the texture boundary by having virtual grass- and cobblestone-textured patterns abutting on a flat (horizontal) ground surface in experiment 1, and by placing a brick wall to interrupt the continuous texture gradient of a flat grass surface in experiment 2. In both instances, observers underestimated the target distance across the texture boundary, compared to the homogeneous-texture ground surface (control). Second, we tested the proposal that the far surface beyond the texture boundary is perceived as slanted upward. For this, we used a virtual checkerboard-textured ground surface that was interrupted by a texture boundary. We found that not only was the target distance beyond the texture boundary underestimated relative to the homogeneous-texture condition, but the far surface beyond the texture boundary was also perceived as relatively slanted upward (experiment 3). Altogether, our results confirm the predictions of the SSIP hypothesis.     

Apparent head position as a basis for a visual aftereffect of prolonged head tilt

A possible explanation of the visual spatial aftereffect following head tilt with eyes closed is that it is an outcome of a proprioceptive aftereffect of head position. If the upright head is apparently tilted then it might be expected that a vertical line in a dark room would also be apparently tilted. This explanation predicts that the direction and magnitude of the visual and proprioceptive aftereffects would correspond. The second of two experiments showed that the trends of the two aftereffects as a function of head tilt angle were different. It was concluded that the visual aftereffect cannot be explained in terms of a proprioceptive aftereffect.     

Internal representation of simple temporal patterns

In this study the imitation of several periodically repeating simple temporal patterns consisting of two or more intervals varying in their duration ratios has been investigated. The errors that subjects typically made in their imitations and the systematic changes that occurred during repeated imitations indicate that both musically trained and untrained subjects map temporal sequences onto an interval structure the nature of which is revealed by studying which patterns are correctly and which incorrectly reproduced. A "beat-based" model for the perception of temporal sequences is proposed. This model states that the first step in the processing of a temporal sequence consists of a segmentation of the sequence into equal intervals bordered by events. This interval is called the beat interval. How listeners select this beat interval is only partly understood. In a second step, intervals smaller than the beat interval are expressed as a subdivision of the beat interval in which they occur. The number of within-beat structures that can be represented in the model is, however, limited. Specifically, only beat intervals that are subdivided into either equal intervals or intervals in a 1:2 ratio fit within the model. The partially hierarchical model proposed, though in need of further elaborations, shows why the number of temporal patterns that can be correctly conceptualized is limited. The relation of the model to other models is discussed.