More accurate size contrast judgments in the Ebbinghaus Illusion by a remote culture.

The Ebbinghaus (Titchener) illusion was examined in a remote culture (Himba) with no words for geometric shapes. The illusion was experienced less strongly by Himba compared with English participants, leading to more accurate size contrast judgments in the Himba. The study included two conditions of inducing stimuli. The illusion was weaker when the inducing stimuli were dissimilar (diamonds) to the target (circle) compared with when they were similar (circles). However, the illusion was weakened to the same extent in both cultures. It is argued that the more accurate size judgments of the Himba derive from their tendency to prioritize the analysis of local details in visual processing of multiple objects, and not from their impoverished naming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parallel memory retrieval in dual-task situations: I. Semantic memory.

Can participants retrieve information about the 2nd of 2 stimuli while they are processing the 1st? Four experiments suggest they can. Reaction times to the 1st stimulus were faster if it came from the same category as the 2nd than if it came from a different category. This category-match effect was observed for letter-digit discrimination (Experiment 1), magnitude and parity judgments about digits (Experiment 2), and lexical decisions (Experiment 3). Experiment 4 showed that the 2nd stimulus could semantically prime the 1st. The category-match effect was observed only when the same task was performed on the 2 stimuli. When the task changed from the Ist stimulus to the 2nd, there was no advantage of a category match. This dependence on task set may explain previous failures to find parallel retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition and the SNARC effect with one- and two-digit numbers.

The SNARC (Spatial Numerical Association of Response Codes) effect is the finding that small numbers elicit faster left than right responses and large numbers elicit faster right than left responses. This effect suggests that numbers activate left-right magnitude-laterality codes and that these codes interact with the selection of left-right responses. In the present research, subjects made parity decisions for one-digit numbers (in Experiment 1) and two-digit numbers (in Experiment 2), and we examined the effect of stimulus repetition on the SNARC effect. With single-digit stimuli, responses were faster and the SNARC effect was eliminated when stimuli were identical on successive trials. With two-digit stimuli, responses were faster when the ones digit was repeated, but the SNARC effect was found regardless of whether the digit was repeated or not. We argue that magnitude-laterality codes are activated in the process of accessing number information in memory and that this process can be short circuited if the visual stimulus matches that on the previous trial. Thus, no SNARC effect is found in Experiment 1 when identical stimuli are presented on successive trials. However, this result is not found in Experiment 2 because successive stimuli do not match even if the ones digit is repeated. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Second-order motions contribute to vection

First- and second-order motions differ in their ability to induce motion aftereffects (MAEs) and the kinetic depth effect (KDE). To test whether second-order stimuli support computations relating to motion-in-depth we examined the vection illusion (illusory self motion induced by image flow) using a vection stimulus (V, expanding concentric rings) that depicted a linear path through a circular tunnel. The set of vection stimuli contained differing amounts of first- and second-order motion energy (ME). Subjects reported the duration of the perceived MAEs and the duration of their vection percept. In Experiment 1 both MAEs and vection durations were longest when the first-order (Fourier) components of V were present in the stimulus. In Experiment 2, V was multiplicatively combined with static noise carriers having different check sizes. The amount of first-order ME associated with V increases with check size. MAEs were found to increase with check size but vection durations were unaffected. In general MAEs depend on the amount of first-order ME present in the signal. Vection, on the other hand, appears to depend on a representation of image flow that combines first- and second-order ME.     

Perceptual effects on remembering: Recollective processes in picture recognition memory.

In 3 experiments, the effects of perceptual manipulations on recollective experience were tested. In Experiment 1, a picture-superiority effect was obtained for overall recognition and Remember judgments in a picture recognition task. In Experiment 2, size changes of pictorial stimuli across study and test reduced recognition memory and Remember judgments. In Experiment 3, deleterious effects of changes in left–right orientation of pictorial stimuli across study and test were obtained for Remember judgments. An alternate framework that emphasizes a distinctiveness–fluency processing distinction is proposed to account for these findings because they cannot easily be accommodated within the existing account of differences in conceptual and perceptual processing for the 2 categories of recollective experience: Remembering and Knowing, respectively (J. M. Gardiner, 1988; S. Rajaram, 1993). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Boredom as a limiting condition on the mere exposure effect.

Three experiments investigating the role of boredom as a limiting condition on R. B. Zajonc's (1968) mere exposure effect are described. In Experiment 1, non-boredom-prone Ss showed significant exposure effects for Welsh figure stimuli, whereas boredom-prone Ss showed no exposure effects at all for these stimuli. In Experiments 2 and 3, complex stimuli (line-drawn optical illusions) produced significantly stronger exposure effects than relatively simple stimuli (Welsh figures). The difference in affect ratings for optical illusion vs. Welsh figure stimuli was greater when Ss rated both types of stimuli (Experiment 2) than when Ss rated only 1 type of stimulus (Experiment 3). Furthermore, Welsh figures showed a decline in affect ratings with increasing exposure frequency in Experiment 2 and an increase in affect ratings with increasing exposure frequency in Experiment 3, suggesting that stimulus "contrast" effects are important in determining affect judgments in mere exposure experiments. Results support the role of boredom as a limiting condition on the mere exposure effect and are consistent with a 2-factor learning-satiation model of the exposure effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading chimpanzee faces: Evidence for the role of verbal labels in categorical perception of emotion.

Categorical perception (CP) occurs when continuously varying stimuli are perceived as belonging to discrete categories. Thereby, perceivers are more accurate at discriminating between stimuli of different categories than between stimuli within the same category (Harnad, 1987; Goldstone, 1994). The current experiments investigated whether the structural information in the face is sufficient for CP to occur. Alternatively, a perceiver's conceptual knowledge, by virtue of expertise or verbal labeling, might contribute. In two experiments, people who differed in their conceptual knowledge (in the form of expertise, Experiment 1; or verbal label learning, Experiment 2) categorized chimpanzee facial expressions. Expertise alone did not facilitate CP. Only when perceivers first explicitly learned facial expression categories with a label were they more likely to show CP. Overall, the results suggest that the structural information in the face alone is often insufficient for CP; CP is facilitated by verbal labeling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast and accentuation effects in category learning.

This study examines the accentuation of perceived intercategory differences. In Experiment 1, 2 sets of trait adjectives were presented, a neutral set and a set of either favorable traits or unfavorable traits. Ss estimated the mean favorability of each set. The mean favorability of the neutral set was then increased or decreased by adding new traits. As predicted, the estimated mean favorability of the neutral set changed more when the set became more distinct from a contextual set than when it became more similar. In Experiment 2, estimated category means were displaced away from each other (contrast effect), and they moved even farther apart when new information increased the variability of trait favorability (accentuation effect). This change was illusory because the actual category means remained constant. Experiment 3, in which trait adjectives described members of 2 novel groups, replicated Experiment 2. The relevance of contrast and accentuation effects to the development and maintenance of differentiated intergroup perceptions is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generalization of learning from picture books to novel test conditions by 18- and 24-month-old children.

Researchers know little about whether very young children can recognize objects originally introduced to them in a picture book when they encounter similar looking objects in various real-world contexts. The present studies used an imitation procedure to explore young children's ability to generalize a novel action sequence from a picture book to novel test conditions. The authors found that 18-month-olds imitated the action sequence from a book only when the conditions at testing matched those at encoding; altering the test stimuli or context disrupted imitation (Experiment 1A). In contrast, the 24-month-olds imitated the action sequence with changes to both the test context and stimuli (Experiment 1B). Moreover, although the 24-month-olds exhibited deferred imitation with no changes to the test conditions, they did not defer imitation with changes to the context and stimuli (Experiment 2). Two factors may account for the pattern of results: age-related changes in children's ability to utilize novel retrieval cues as well as their emerging ability to understand the representational nature of pictures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localizing the first position of a moving stimulus: the Fr?hlich effect and an attention-shifting explanation

When subjects are asked to determine where a fast-moving stimulus enters a window, they typically do not localize the stimulus at the edge, but at some later position within that window (Fr?hlich effect). We report five experiments that explored this illusion. An attentional account is tested, assuming that the entrance of the stimulus in the window initiates a focus shift toward it. While this shift is under way, the stimulus moves into the window. Because the first phenomenal (i.e., explicitly reportable) representation of the stimulus will not be available before the end of the focus shift, the stimulus is perceived at some later position. In Experiment 1, we established the Fr?hlich effect and showed that it size depends on stimulus parameters such as movement speed and movement direction. In Experiments 2 and 3, we examined the influence of eye movements and tested whether the effect changed when the stimuli were presented within a structural background or when they started from different eccentricities. In Experiments 4 and 5, specific predictions from the attentional model were tested: In Experiment 4 we showed that the processing of the moving stimulus benefits from a preceding peripheral cue indicating the starting position of the subsequent movement, which induces a preliminary focus shift to the position where the moving stimulus would appear. As a consequence the Fr?hlich effect was reduced. Using a detection task in Experiment 5, we showed that feature information about the moving stimulus is lost when it falls into the critical interval of the attention shift. In conclusion, the present attentional account shows that selection mechanisms are not exclusively space based; rather, they can establish a spatial representation that is also used for perceptual judgement--that is, selection mechanisms can be space establishing as well.     

Detection of Kanji words in a rapid serial visual presentation task.

In 3 experiments, lists of 12 Kanji words were rapidly presented in the same position, and participants reported a red target word embedded in green distractor words. Two lists were used: same and different category. A tendency toward category priming was found at longer durations. Frequency of target localization indicated that participants familiar with Kanji had a greater tendency to report the word immediately preceding the target. These pretarget intrusion errors dominated the posttarget intrusion errors, when the luminance of red and green stimuli were equated (Experiment 2), and when the response was recall (Experiments 1 and 2) or recognition (Experiment 3). In contrast, participants unfamiliar with Kanji made posttarget intrusion errors as frequently as pretarget intrusion errors (Experiment 3), suggesting that knowledge of Kanji influences the integration of color and form codes in visual information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer across delayed discriminations: II. Differences in the substitutability of initial versus test stimuli.

In 2 experiments, pigeons were trained on, and then transferred to, delayed simple discriminations in which the initial stimuli signalled reinforcement versus extinction following a retention interval. Experiment 1 showed that discriminative responding on the retention test transferred to novel test stimuli that had appeared in another delayed simple discrimination but not to stimuli having the same reinforcement history off-baseline. By contrast, Experiment 2 showed that performances transferred to novel initial stimuli whether they had been trained on-baseline or off-baseline. These results suggest that the test stimuli in delayed simple discriminations acquire control over responding only in the memory task itself. On the other hand, control by the initial stimuli, if coded as outcome expectancies, does not require such task-specific training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in the perception and learning of artistic style categories.

Adult age differences in conceptual behavior were studied using informationally complex stimuli from real-world categories: paintings by two impressionist artists. In Experiment 1 we examined perceptions of category structure by having subjects sort paintings according to style similarity. Young adults were observed to depend more on abstract information in making style judgments, whereas older adults relied more on similarity in content. This resulted in different category structures between age groups, but similarity judgments in both groups appeared to correspond to actual style differences between the two artists. In Experiment 2, learning efficiency was shown to increase with a painting's category centrality, but older adults had particular trouble learning noncentral items. At transfer, both age groups were able to use abstracted central tendency information to categorize new paintings, although young adults appeared to have better access to information about specific category exemplars from acquisition. The results are generally consistent with those from studies using simpler artificial stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization of speech by infants: Support for speech-sound prototypes.

This study tested 6-month-old infants' categorization of speech stimuli to investigate whether infants organize speech categories around "prototypes." In Experiment 1, infants first discriminated single "good" exemplars from two different vowel categories. They were then tested with 64 novel exemplars, 32 from each vowel category. The test stimuli varied in the degree to which they conformed to adult-defined prototypes of the two categories. The results showed that infants correctly sorted the novel stimuli over 90% of the time. In Experiment 2, we trained two groups of infants, one with a good (prototypical) exemplar from a vowel category and the other with a poor (nonprototypical) exemplar. Then we tested both groups with 16 novel exemplars from that same vowel category. Generalization to novel members of the category was significantly greater following exposure to the prototypical exemplar. Results are consistent with a model of speech perception that holds that young human infants organize vowel categories around prototypes. This may contribute to their seemingly efficient processing of speech information, even in the first half year of life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison and Contrast in Perceptual Categorization.

People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Real and virtual borders in the Poggendorff illusion

The strength of the Poggendorff illusion has been determined by a nulling method for the classical as well as other configurations of the central inducing region. Compared to a uniform field, an inducing rectangle with very low contrast produces a marked illusion, which saturates at a Michelson contrast of about 0.1. With virtual borders of the Kanizsa type there is a weak illusion and this effect is attenuated when the 'pacman' sectors are occluded. Texture borders without luminance contrast induce a stronger illusion. These results are discussed in relation to earlier data for contrast dependence of Vernier acuity and for the orientation discrimination and tilt illusion with real and virtual borders.     

Causal status and coherence in causal-based categorization.

Research has documented two effects of interfeature causal knowledge on classification. A causal status effect occurs when features that are causes are more important to category membership than their effects. A coherence effect occurs when combinations of features that are consistent with causal laws provide additional evidence of category membership. In this study, we found that stronger causal relations led to a weaker causal status effect and a stronger coherence effect (Experiment 1), that weaker alternative causes led to stronger causal status and coherence effects (Experiment 2), and that “essentialized” categories led to a stronger causal status effect (Experiment 3), albeit only for probabilistic causal links (Experiment 4). In addition, the causal status effect was mediated by features' subjective category validity, the probability they occur in category members. These findings were consistent with a generative model of categorization but inconsistent with an alternative model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further analysis of perception of the standard Müller-Lyer figures in pigeons (Columba livia) and humans (Homo sapiens): Effects of length of brackets.

Nakamura, Fujita, Ushitani, & Miyata (2006) have shown that pigeons perceive the standard Müller-Lyer illusion. In this report, the authors examined effects of bracket sizes on perception of this illusion in pigeons (Columba livia) and humans (Homo sapiens). In Experiment 1, three pigeons were retrained to classify six lengths of target lines into “long” and “short” by pecking two keys on the monitor, ignoring the two brackets oriented toward the same direction. In the tests that followed, the standard Müller-Lyer figures of different bracket sizes were presented. All birds chose “long” more frequently for the figures having inward-pointing brackets (>), regardless of bracket sizes. The overestimation of the target lines of inward-pointing figures continued to increase in pigeons, whereas it decreased as the bracket size became longer in humans (Experiment 2). The results suggest that these two species perceive the standard Müller-Lyer illusion with long brackets in different ways. Perhaps pigeons might not perceive illusions induced by contrast with the surrounding stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of the role of associative inhibition in perceptual learning by means of the same-different task.

In Experiment 1a, participants were exposed, over a series of trials, to separate presentations of 2 similar checkerboard stimuli, AX and BX (where X represents a common background). In one group, AX and BX were presented on alternating trials (intermixed), in another, they were presented in separate blocks of trials (blocked). The intermixed group performed to a higher standard than the blocked group on a same-different test. A superiority of intermixed over blocked exposure was also evident in a within-subject design (Experiment 1b) and when the test required discrimination between a preexposed stimulus and the background (e.g., AX vs. X), even if the background changed between preexposure and test (AY vs. Y) (Experiment 2). In Experiment 3, the intermixed/blocked effect was observed when, in preexposure, stimulus presentations were alternated with the background alone (e.g., AX/X). This suggests that the perceptual learning effect is not the consequence of inhibitory associations between unique features but to increased salience of those features. Experiment 4 confirmed this finding and also ruled out an account of the effect in terms of trial spacing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The changing composition of abstracted categories under manipulations of decisional change, choice difficulty, and category size.

The role of decisional factors in category abstraction was investigated. The major prediction was that a change in instructional set would primarily affect the more difficult choices of a category (boundary contraction hypothesis), with this outcome modulated by category size. Subjects classified patterns into three prototype categories until they reached an errorless criterion; then they immediately took a transfer test under a conservative or liberal set. Category size was varied independently of category frequency in Experiment 1; in Experiment 2, category size functioned as a between-subjects variable. The results showed that instructional set affected new, but not old, instances, with this effect additive across choice difficulty and category size. The boundary contraction hypothesis was rejected, and a two-stage model of classification was proposed to account for the results. A compositional analysis revealed that far greater levels of learning may be needed before selective decision making can occur. (PsycINFO Database Record (c) 2010 APA, all rights reserved)