Search

The human olfactory psychophysical literature is rich with anecdotal reports of variation in the perceived quality between weak and strong concentrations of the same odour (Wilson and Stevenson 2006). Psychophysical experiments using animals have also found similar effects of concentration on odour quality. The proboscis extension reflex (PER) is an appetitive Pavlovian conditioning assay that has been used to investigate olfactory stimuli in the honeybee. In this series of experiments I aim to identify the sensitivity of honeybees to changes in odorant concentration across the range of a honeybee’s sensorium (0.01–100 Pa). I compared generalisation to test odours that differed in molecular identity, odour concentration or both and found that large changes in odorant concentration (1,000 fold change) can produce greater shifts in perceptual similarity than a change in the odorant’s molecular structure. Our findings suggest a failure in concentration invariance when identical odours differ greatly in concentration. I also found poorer olfactory sensitivity (between identical odours of differing concentration) and acuity (between novel odours of identical concentration) at low odour concentrations (0.01 Pa).

Our everyday visual experience frequently involves searching for objects in clutter. Why are some searches easy and others hard? It is generally believed that the time taken to find a target increases as it becomes similar to its surrounding distractors. Here, I show that while this is qualitatively true, the exact relationship is in fact not linear. In a simple search experiment, when subjects searched for a bar differing in orientation from its distractors, search time was inversely proportional to the angular difference in orientation. Thus, rather than taking search reaction time (RT) to be a measure of target–distractor similarity, we can literally turn search time on its head (i.e. take its reciprocal 1/RT) to obtain a measure of search dissimilarity that varies linearly over a large range of target–distractor differences. I show that this dissimilarity measure has the properties of a distance metric, and report two interesting insights come from this measure: First, for a large number of searches, search asymmetries are relatively rare and when they do occur, differ by a fixed distance. Second, search distances can be used to elucidate object representations that underlie search – for example, these representations are roughly invariant to three-dimensional view. Finally, search distance has a straightforward interpretation in the context of accumulator models of search, where it is proportional to the discriminative signal that is integrated to produce a response. This is consistent with recent studies that have linked this distance to neuronal discriminability in visual cortex. Thus, while search time remains the more direct measure of visual search, its reciprocal also has the potential for interesting and novel insights.

Dong et al. examined the ability of 51 computational feature sets to estimate human perceptual texture similarity; however, none performed well for this task. While it is well-known that the human visual system is extremely adept at exploiting longer-range aperiodic (and periodic) “contour” characteristics in images, none of the investigated feature sets exploit higher order statistics (HOS) over larger image regions ( $> 19\times 19$ pixels). We, therefore, hypothesise that long-range HOS, in the form of contour data, are useful for perceptual texture similarity estimation. We present the results of a psychophysical experiment that shows that contour data are more important, than local image patches, or global second-order data, to human observers for this task. Inspired by this finding, we propose a set of perceptually motivated image features (PMIF) that encode the long-range HOS computed from spatial and angular distributions of contour segments. We use two perceptual texture similarity estimation tasks to compare PMIF against the 51 feature sets referred to above and four commonly used contour representations. This new feature set is also examined in the context of two additional tasks: sketch-based image retrieval and natural scene recognition. The results show that the proposed feature set performs better, or at least comparably to, all the other feature sets. We attribute this promising performance to the fact that the proposed feature set exploits both short-range and long-range HOS.

Perceptual similarity between stimuli is often assessed via generalization, the response to stimuli that are similar to the one which was previously conditioned. Although conditioning procedures are variable, studies on how this variation may affect perceptual similarity remain scarce. Here, we use a combination of behavioural and computational analyses to investigate the influence of olfactory conditioning procedures on odour generalization in ants. Insects were trained following either absolute conditioning, in which a single odour (an aldehyde) was rewarded with sucrose, or differential conditioning, in which one odour (the same aldehyde) was similarly rewarded and another odour (an aldehyde differing in carbon-chain length) was punished with quinine. The response to the trained odours and generalization to other aldehydes were assessed. We show that olfactory similarity, rather than being immutable, varies with the conditioning procedure. Compared with absolute conditioning, differential conditioning enhances olfactory discrimination. This improvement is best described by a multiplicative interaction between two independent processes, the excitatory and inhibitory generalization gradients induced by the rewarded and the punished odour, respectively. We show that olfactory similarity is dramatically shaped by an individual's perceptual experience and suggest a new hypothesis for the nature of stimulus interactions underlying experience-dependent changes in perceptual similarity.

This study investigates how English coda [m] is adapted into Standard Mandarin (SM) loanwords both in the existing corpora and in perceptual similarity adaptation data from monolingual SM and bilingual SM-English speakers. The nasal [m] in coda position is prohibited in SM. Deletion, nasal place change ([m]-->[n]/[ŋ]) and vowel epenthesis are the possible repair strategies. The generalizations identified in the corpora indicate that deletion never occurs (cf. Preservation Principle from Paradis 1996, Paradis & Lacharité 1997). Vowel epenthesis appears in SM when English coda [m] is in word-medial and word final positions. Nasal place change appears when English coda [m] is followed by a labial obstruent. Variable adaptations happen when English coda [m] is followed by an obstruent. The experimental results show that (i) the bilingual experimental strategies for nonce word adaptations are similar to the patterns observed in the SM loanwords corpora and (ii) monolinguals’ adaptation patterns are more variable due to greater dependence on perceptual cues. The fact that monolinguals and bilinguals differ in the extent to which they employ perceptual cues and phonological features/constraints for loanword adaptations challenges a pure perception-based account of loanword adaptation.

People assess real-time events by relying on knowledge and experience accumulated in a conceptually referenced framework. The difference in assessment will prompt an incongruity for reconciliation. The authors propose an integrated conceptual framework with evidence reasoned pathways for consumers to assess product to become brand. Product information is transcended through (1) perceptual similarity cataloguing, (2) specific-aimed brand fit, and (3) general-context brand consistency to become relevant brand in the mind of consumers by enculturation conformance, subject to contextual limitation and modification. We conducted a contrarian study by having consumers assess a primed mimic brand in comparison with its authentic one using the proposed conceptual approaches. The empirical results validate the framework and reveal the assessment of mimic brand from its authentic origin primarily goes beyond the product functionality relative to utility benefits, and largely determined by value congruence process on enculturation conformance in context.

Maljkovic and Nakayama (1994) demonstrated memory influences in singleton search from one trial to the next, an effect they termed priming of pop-out (PoP). This effect was described as resulting from the persistence of an implicit memory trace, the influence of which could be observed for around five to eight subsequent trials. The seemingly short-lived nature of this priming effect has been attributed to decay of the underlying memory representation that occurs when attention is directed to intervening search items, even when such items are perceptually dissimilar from the search trials upon which PoP is measured (Maljkovic & Nakayama, 2000). The present study reexamines the role of perceptual similarity as a mechanism of interference by examining the influence on PoP of rare search trials that were perceptually distinct with respect to the other, common trials. Long-lasting (n - 16) PoP was observed for rare trials that were composed of distinct target/distractor colors, suggesting that PoP can be observed across at least twice as many trials as has previously been reported. Thus, the time span across which PoP can be measured depends heavily on the nature of the intervening search displays, a result that must be accommodated by current theoretical accounts of PoP.

Artists have long explored the way in which we see the world, and they have developed their own tools to portray their vision. The present study investigated whether the compositional information in paintings, an artistic device invented by artists, is utilized when people view paintings. In Experiment 1, we categorized paintings depending on their compositions through experts’ ratings. Using the stimuli from Experiment 1, Experiment 2 tested if the compositional information interferes with a target detection task. We found that the false alarms increased when the targets and distracters had the same composition compared to when they were different. Finally, Experiments 3A and 3B examined whether composition information influences the perceptual similarity of paintings. Through a multi-dimensional scaling analysis, we first showed that paintings with the same composition were proximately located in the mental space (Experiment 3A). Using this distance from the MDS analysis, we found that performance on the target detection task decreased as this distance became close (Experiment 3B). These results suggest that people make use of compositions in paintings, thus providing a possible link between artworks and the human visual system.

In this study, we investigated the nature of cross-modal associations between colors and vowels. In Experiment 1, we examined the patterns of synesthetic correspondence between colors and vowels in a perceptual similarity experiment. The results were as follows: red was chosen for /a/, yellow was chosen for /i/, and blue was chosen for /o/ significantly more than any other vowels. Interestingly this pattern of correspondence is similar to the pattern of colored hearing reported by synesthetes. In Experiment 2, we investigated the robustness of these cross-modal associations using an implicit association test (IAT). A clear congruence effect was found. Participants responded faster in congruent conditions (/i/ and yellow, /o/ and blue) than in incongruent conditions (/i/ and blue, /o/ and yellow). This result suggests that the weak synesthesia between vowels and colors in non-synesthtes is not the fact of mere conscious choice, but reflects some underlying implicit associations.

Previous studies have found that talkers converge or diverge in phonetic form during a single conversational session or as a result of long-term exposure to a particular linguistic environment. In the current study, five pairs of previously unacquainted male roommates were recorded at four time intervals during the academic year. Phonetic convergence over time was assessed using a perceptual similarity test and measures of vowel spectra. There were distinct patterns of phonetic convergence during the academic year across roommate pairs, and perceptual detection of convergence varied for different linguistic items. In addition, phonetic convergence correlated moderately with roommates' self-reported closeness. These findings suggest that phonetic convergence in college roommates is variable and moderately related to the strength of a relationship.

This paper presents evidence from a series of perception experiments that non-local restrictions on laryngeal features are restrictions on contrast. First, I present results from two perception experiments and show that the perceptual strength of a contrast in ejection or aspiration correlates with the typology of long-distance restrictions on these segments. I then claim that a language may disallow roots with two ejectives because roots of this type are judged too perceptually similar to a root with only one ejective. Second, I claim that non-local laryngeal restrictions involve restrictions on auditory properties. A third experiment supports the idea that long VOT is relevant in explaining the interaction of ejectives and aspirates in Quechua, thus supporting the proposal that auditory dimensions of contrast are relevant to phonology ( Flemming, 1995; Steriade, 1997 ).

The goal of the present study was to evaluate the claim that category labels affect children’s judgments of visual similarity. We presented preschool children with discriminable and identical sets of animal pictures and asked them to make perceptual judgments in the presence or absence of labels. Our findings indicate that children who are asked to make perceptual judgments about identical items judge discriminable items less accurately when making subsequent similarity judgments. Thus, labels do not generally affect children’s perceptual similarity judgments; rather, children’s reliance on labels to make similarity judgments appears to be attributable to flaws in the methodological approaches used in prior studies. These results have implications for the role of perceptual and conceptual information in children’s categorization and induction.

Various factors could conceivably promote the accuracy of guesses during a recognition test. Two that we identified in previous studies are forced-choice testing format and high perceptual similarity between the repeat target and novel foil. In restricted circumstances, the relative perceptual fluency of the target can be compared with that of the foil and used as a reliable cue to guide accurate responses that occur without explicit retrieval—a phenomenon we referred to as “implicit recognition.” In this issue, Jeneson and colleagues report a failure to replicate accurate guesses and also a tendency on the part of subjects to hazard guesses infrequently, even though testing circumstances were very similar to those that we used. To resolve this discrepancy, we developed a simple manipulation to encourage either guessing or confident responding. Encouraging guessing increased both the prevalence of guesses and the accuracy of guesses in a recognition test, relative to when confident responding was encouraged. When guessing was encouraged, guesses were highly accurate (as in our previous demonstrations of implicit recognition), whereas when confident responding was encouraged, guesses were at chance levels (as in Jeneson and colleagues' data). In light of a substantial literature showing high accuracy despite low confidence in certain circumstances, we infer that both the prevalence and accuracy of guessing can be influenced by whether subjects adopt guessing-friendly strategies. Our findings thus help to further characterize conditions likely to promote implicit recognition based on perceptual fluency.

With the heightened interest on medication mix-ups in the media, improvements to patient health and safety are a natural focus for research in medical human factors. Specifically, this project sought to answer the question ‘Does Color Matter?’ with respect to medication containers/labels and their contribution to look-a-like medication mix-ups. Participants were asked to rate the perceptual similarity of pairs of medication ampoules and vials. Ratings were analyzed using Multi-Dimensional Scaling (MDS). A three dimensional solution provided the best fit of the results. Participants rated medication ampoules as highly similar if they shared the same glass color (dimension 1), label color (dimension 2), and label pattern (dimension 3). Ratings of medication vials were similar if they had similar glass color (dimension 1), label pattern (dimension 2) and label color (dimension 3). The results of this study show that color is an important feature used by nurses when judging medications on their similarity. Discussion centers on the practical implications of the results on medication look a-like confusions.

In a perceptual assimilation task, 16 Russian speakers categorized American English (AE) vowels [i[see text], I, epsilon, ae[see tedxt], a[see text], u[see text]] in /Vp/ disyllables into Russian (RU) response categories and rated their perceived goodness on a 9-point Likert scale. Cross-language discriminant analysis established acoustic similarities to Russian vowels. For all but AE [epsilon], acoustic similarity predicted modal assimilation responses. Russian listeners consistently assimilated AE point vowels to their Russian counterparts, whereas assimilation of the remaining vowels was less consistent. These acoustic and perceptual similarity patterns provide a baseline for future studies of AE vowel discrimination by Russian learners of English.

Perception entails not only sensory input (e.g., merely seeing), but also subsidiary motor processes (e.g., moving the eyes); such processes have been neglected in research on aesthetic preferences. To fill this gap, the present research manipulated the fluency of perceptual motor processes independently from sensory input and predicted that this increased fluency would result in increased aesthetic preference for stimulus movements that elicited the same motor movements as had been previously trained. Specifically, addressing the muscles that move the eyes, I trained participants to follow a stimulus movement without actually seeing it. Experiment 1 demonstrated that ocular-muscle training resulted in the predicted increase in preference for trained stimulus movements compared with untrained stimulus movements, although participants had not previously seen any of the movements. Experiments 2 and 3 showed that actual motor matching and not perceptual similarity drove this effect. Thus, beauty may be not only in the eye of the beholder, but also in the eyes’ movements.

Certain odours and certain tastes appear to share common perceptual properties. One example is sweetness, a perceptual experience that results from stimulation of taste receptors on the tongue typically by sugars. The experiment here examined for evidence of this perceptual similarity using a novel and indirect test. Participants were exposed six times each, to three odours (strawberry, caramel, and oregano) and three tastes (sucrose, saline, and citric acid). Following a 10-min interval, participants were given a surprise frequency estimation task, in which they had to judge how often each stimulus had occurred. If sweet-smelling strawberry and caramel odours really do share this perceptual characteristic in common with sweet tasting sucrose, then frequency estimates for sucrose should be overestimated relative to non-sweet tastes. Not only was this observed, but frequency estimates for sweet tastes were also found to correlate with (1) evaluations from a later test of similarity between these sweet smells and sucrose, and (2) the degree to which these odours smelled sweet. These findings suggest a shared perceptual feature between such odours and sucrose - sweetness - under conditions where no judgment of perceptual quality was required.

Listeners demonstrate reliable perceptual biases favoring voices speaking their native language versus those speaking a foreign language. This “language-familiarity effect” for voice processing has been found even for perceptual similarity judgments: Voices speaking listeners’ native language sound less alike, even when those recordings have been rendered incomprehensible via time-reversal. Here, we sought to replicate and extend this finding of linguistic effects on voice similarity. Native English- and Mandarin-speaking listeners (both N = 40) rated the perceptual similarity of voices speaking English or Mandarin (both N = 20) for either time-reversed or forward speech. Both listener groups tended to find Mandarin-speaking voices more dissimilar, but this effect was reduced for English-speaking listeners, especially for forward speech. Perceptual similarity judgments of voices were always highly correlated between listener groups and between forward/time-reversed speech. Acoustic measurements (voice fun...

Perceptual grouping is usually defined by principles that associate distinct elements by virtue of image properties, such as proximity, similarity, and occurrence within common regions. What role does learning play in forming a perceptual group? This study provides evidence that learning of shape associations leads to perceptual grouping. Subjects were repeatedly exposed to pairs of unique shapes that co-occurred within a common region. The common region cue was later removed in displays composed of these shapes, and the subjects searched the display for two adjacent shapes of the same color. The subjects were faster at locating the color repetition when the adjacent shapes with the same color came from the same trained groups than when they were composed of two shapes from different trained groups. The effects were perceptual in nature: Learned pairings produced spatial distortions similar to those observed for groups defined by perceptual similarity. A residual grouping effect was observed even when the shapes in the trained group switched their relative positions but was eliminated when each shape was inverted. These results indicate that statistical co-occurrence with explicit grouping cues may form an important component of perceptual organization, determining perceived scene structure solely on the basis of past experience.

People usually categorize objects more quickly at the basic level (e.g., "dog") than at the subordinate (e.g., "collie") or superordinate (e.g., "animal") levels. Notable exceptions to this rule include objects of expertise, faces, or atypical objects (e.g., "penguin," "poodle"), all of which show faster than normal subordinate-level categorization. We hypothesize that the subordinate-level reaction time advantage for faces is influenced by their discriminability relative to other faces in the stimulus set. First, we replicated the subordinate-level advantage for faces (Experiment 1) and then showed that a basic-level advantage for faces can be elicited by increasing the perceptual similarity of the face stimuli, making discrimination more difficult (Experiment 2). Finally, we repeated both effects within subjects, showing that individual faces were slower to be categorized in the context of similar faces and more quickly categorized among diverse faces (Experiment 3).

The free classification paradigm and its potential application to perceptual acoustic and auditory research are summarized. Specific methods for the application of the auditory free classification paradigm in speech research are then described, including techniques for stimulus preparation, data collection, and statistical analysis, based on a sample auditory free classification study of regional dialect variation. The results suggest that auditory free classification is a promising paradigm for examining the perceptual classification and similarity of speech and nonspeech auditory stimulus materials.

Abstract. Foreign accent has been assumed to be closely related to the degree of articulatory, acoustic and perceptual similarity between L1 and L2 sounds. This study examined cross-language acoustic and perceptual similarities between Korean and English sibilant fricatives: Korean [—tense] /s/ and [+tense] /s*/ vs. English alveolar /s/ and palato-alveolar /∫/. To determine acoustic similarity, two parameters were measured: duration and spectral peak frequency. A Same-Different (AX) discrimination task investigated listeners' perceived similarity judgments between pairs of sibilants. In most cases, the acoustic characterizations led to correct predictions about differences in listeners' perceptions. However, results showed several disparities between acoustic similarity and perceived similarity. These cases necessarily involve acoustic dimensions other than the two measured here; probable candidates are voice quality on a following vowel, and lip rounding, with its spectral lowering effects. Cases of mismatch between acoustic and perceptual characterizations are fruitful areas for examining additional acoustic characteristics that may be responsible for listeners' ability to distinguish sounds. Acoustic and perceptual characterizations in tandem provide the best method of establishing areas of difference between the sounds of different languages, and in turn of establishing ways to teach L2 sounds to learners.

Transposing two internal letters of a word produces a perceptually similar item (e.g., CHOLOCATE being processed as CHOCOLATE). To determine the precise nature of the encoding of letter position within a word, we examined the effect of the number of intervening letters in transposed-letter effects with a masked priming procedure. In Experiment 1, letter transposition could involve adjacent letters (chocloate-CHOCOLATE) and nonadjacent letters with two intervening letters (choaolcte-CHOCOLATE). Results showed that the magnitude of the transposed-letter priming effect – relative to the appropriate control condition – was greater when the transposition involved adjacent letters than when it involved nonadjacent letters. In Experiment 2, we included a letter transposition condition using nonadjacent letters with one intervening letter (cholocate-CHOCOLATE). Results showed that the transposed-letter priming effect was of the same size for nonadjacent transpositions that involved one or two intervening letters. In addition, transposed-letter priming effects were smaller in the two nonadjacent conditions than in the adjacent condition. We examine the implications of these findings for models of visual-word recognition.

Ready-to-drinks (RTDs) are composed of an alcoholic component and a soft-drink base and are primarily consumed by a youth market. The authors explored whether liking and experience with an RTD soft-drink base predicts liking for the RTD. Participants (N = 350) from ages 12 to 30 years sampled 3 RTDs and their respective soft-drink and alcoholic components. For milk- and fruit-based RTDs, liking for and familiarity with their soft-drink base was the best predictor of liking for and familiarity with the RTD itself. For the Coke-based RTD, familiarity with and liking for bourbon best predicted familiarity with and liking for the RTD. All of these effects were consistent across blind and nonblind testing. The authors' results suggest that where there is perceptual similarity between the RTD and its soft-drink base, these beverages may provide an easy transition into alcohol consumption for novice drinkers.

Mammals have adapted to a variety of natural environments from underwater to aerial and these different adaptations have affected their specific perceptive and cognitive abilities. This study used a computer-controlled touchscreen system to examine the visual discrimination abilities of horses, particularly regarding size and shape, and compared the results with those from chimpanzee, human and dolphin studies. Horses were able to discriminate a difference of 14% in circle size but showed worse discrimination thresholds than chimpanzees and humans; these differences cannot be explained by visual acuity. Furthermore, the present findings indicate that all species use length cues rather than area cues to discriminate size. In terms of shape discrimination, horses exhibited perceptual similarities among shapes with curvatures, vertical/horizontal lines and diagonal lines, and the relative contributions of each feature to perceptual similarity in horses differed from those for chimpanzees, humans and dolphins. Horses pay more attention to local components than to global shapes., ウマの目からの眺め：ウマ、イルカ、チンパンジー、ヒトにおける図形知覚の比較. 京都大学プレスリリース. 2015-11-26.

We present our ongoing work on a creativity assistance tool called I-get. The tool is based on the hypothesis that perceptual similarity between a pair of images, at a subconscious level, plays a key role in generating creative conceptual associations and metaphorical interpretations. The tool "I-get" is designed to assist users to create novel ideas and metaphorical associations primed by algorithmic perceptual similarity between two images and alternative conceptual associations given by users.

Perceptual similarity is an important property of multiple stimuli. Its computation supports a wide range of cognitive functions, including reasoning, categorization, and memory recognition. It is important, therefore, to determine why previous research has found conflicting effects of inter-item similarity on visual working memory. Studies reporting a similarity advantage have used simple stimuli whose similarity varied along a featural continuum. Studies reporting a similarity disadvantage have used complex stimuli from either a single or multiple categories. To elucidate stimulus conditions for similarity effects in visual working memory, we tested memory for complex stimuli (faces) whose similarity varied along a morph continuum. Participants encoded 3 morphs generated from a single face identity in the similar condition, or 3 morphs generated from different face identities in the dissimilar condition. After a brief delay, a test face appeared at one of the encoding locations for participants to make a same/different judgment. Two experiments showed that similarity enhanced memory accuracy without changing the response criterion. These findings support previous computational models that incorporate featural variance as a component of working memory load. They delineate limitations of models that emphasize cortical resources or response decisions.

The ability to extract the mean of features from a rapidly viewed, heterogeneous array of objects has been demonstrated for a number of different visual properties. Few studies have previously investigated the rapid averaging of color; those that did had insufficient stimulus control or inappropriate methods. This study reports three experiments that directly test observers' ability to extract the mean hue from a rapidly presented, multielement color ensemble. In Experiment 1, ensembles varied in number of elements and number of colors. It was found that averaging was harder for ensembles with more colors but that changing the number of elements had no effect on accuracy, supportive of a distributed-attention account of rapid color averaging. Experiment 2a manipulated the hue range present in any single ensemble (varying the perceptual difference between ensemble elements) while still varying the number of colors. Range had a strong effect on ability to pick the mean hue. Experiment 2b found no effect of color categories on the accuracy or speed of mean selection. The results indicate that perceptual difference of elements is the dominant factor affecting ability to average rapidly seen color ensembles. Findings are discussed both in the context of perception and memory of multiple colors and ensemble perception generally.

We present a novel way of accounting for similarity judgments. Our approach posits that similarity stems from three main sources—familiarity, priming, and inherent perceptual likeness. Here, we explore each of these constructs and demonstrate their individual and combined effectiveness in explaining similarity judgments. Using these three measures, our account of similarity explains ratings of simple, color-based perceptual stimuli that display asymmetry effects, as well as more complicated perceptual stimuli with structural properties; more traditional approaches to similarity solve one or the other and have difficulty accounting for both. Overall, our work demonstrates the importance of each of these components of similarity in explaining similarity judgments, both individually and together, and suggests important implications for other similarity approaches.

Recent studies using the delayed matching-to-sample (DMS) paradigm indicate that monkeys' auditory short-term memory (STM) is susceptible to proactive interference (PI). During the task, subjects must indicate whether sample and test sounds separated by a retention interval are identical (match) or not (nonmatch). If a nonmatching test stimulus also occurred on a previous trial, monkeys are more likely to incorrectly make a “match” response (item-specific PI). However, it is not known whether PI may be caused by sounds presented on prior trials that are similar, but nonidentical to the current test stimulus (item-nonspecific PI). This possibility was investigated in two experiments. In Experiment 1, memoranda for each trial comprised tones with a wide range of frequencies, thus minimizing item-specific PI and producing a range of frequency differences among nonidentical tones. In Experiment 2, memoranda were drawn from a set of eight artificial sounds that differed from each other by one, two, or three acoustic dimensions (frequency, spectral bandwidth, and temporal dynamics). Results from both experiments indicate that subjects committed more errors when previously-presented sounds were acoustically similar (though not identical) to the test stimulus of the current trial. Significant effects were produced only by stimuli from the immediately previous trial, suggesting that item-nonspecific PI is less perseverant than item-specific PI, which can extend across noncontiguous trials. Our results contribute to existing human and animal STM literature reporting item-nonspecific PI caused by perceptual similarity among memoranda. Together, these observations underscore the significance of both temporal and discriminability factors in monkeys' STM.

Patients with schizophrenia show marked memory deficits which have a negative impact on their functioning and life quality. Recent models suggest that such deficits might be attributable to defective pattern separation (PS), a hippocampal-based computation involved in the differentiation of overlapping stimuli and their mnemonic representations. One previous study on the topic concluded in favour of pattern separation impairments in the illness. However, this study did not clarify whether more elementary recognition and/or visual discrimination deficits could explain observed group differences. To address this limitation we investigated pattern separation in 22 schizophrenic patients and 24 healthy controls with the use of a task requiring individuals to classify stimuli as repetitions, novel or similar compared to a previous familiarisation phase. In addition, we employed a visual discrimination task involving perceptual similarity judgments on the same images. Results revealed impaired performance in the patient group; both on baseline measure of pattern separation as well as an index of pattern separation rigidity. However, further analyses demonstrated that such differences could be fully explained by recognition and visual discrimination deficits. Our findings suggest that pattern separation in schizophrenia is predicated on earlier recognition and visual discrimination problems. Furthermore, we demonstrate that future studies on pattern separation should include appropriate measures of recognition and visual discrimination performance for the correct interpretation of their findings.

Our ability to maintain small amounts of information in mind is critical for successful performance on a wide range of tasks. However, it remains unclear exactly how this maintenance is achieved. One possibility is that it is brought about using mechanisms that overlap with those used for attentional control. That is, the same mechanisms that we use to regulate and optimize our sensory processing may be recruited when we maintain information in visual short-term memory (VSTM). We aimed to test this hypothesis by exploring how distracter filtering is modified by concurrent VSTM load. We presented participants with sequences of target items, the order and location of which had to be maintained in VSTM. We also presented distracter items alongside the targets, and these distracters were graded such that they could be either very similar or dissimilar to the targets. We analyzed scalp potentials using a novel multiple regression approach, which enabled us to explore the neural mechanisms by which the participants accommodated these variable distracters on a trial-to-trial basis. Critically, the effect of distracter filtering interacted with VSTM load; the same graded changes in perceptual similarity exerted effects of a different magnitude depending upon how many items participants were already maintaining in VSTM. These data provide compelling evidence that maintaining information in VSTM recruits an overlapping set of attentional control mechanisms that are otherwise used for distracter filtering. ispartof: Frontiers in Human Neuroscience vol:8 issue:JAN pages:1025- ispartof: location:Switzerland status: published

While there is a great need, there is a general paucity of research dealing with inter-country studies in organizational behavior literature. This is especially so with regard to comparing the organizational buyers in diverse socio-economic and industrial settings. This paper analyzes and reports differences and similarities between the American and the Indian industrial buyers with regard to their °choice criteria’ in selecting vendors. Similarities and differences between the two groups of industrial buyers were statistically analyzed across sixty four vendor attributes and two product buying situations -- standard and special.

In July 1995, I was surprised and delighted to receive by US mail from W.V. Quine a draft of a short paper titled ‘Preestablished Harmony’ that responds to Ebbs (1994), my review of Quine (1992), the revised edition of his book Pursuit of Truth. A few days later Quine sent me another short paper titled ‘Response to Gary Ebbs’ and a brief cover letter in which he wrote: Here is a revision of the four pages I sent you last week. It was sparked by discussions with Burt Dreben. I mean to submit it or a further version to the Phil Review.

In my ill-organized way I have only now, a year late, come upon Gary Ebbs’ brilliant review of my Pursuit of Truth.1 I am flattered by his scholarly command of my writings and impressed with his penetration to crucial points. I am thankful, amid all this, for his evidently having missed vital points in my evolving views; for other readers will have missed them a fortiori, and I am now alerted to make amends for my inadequate exposition.

In my ill-organized way I have only now, a year late, come upon Gary Ebbs’ brilliant review of my Pursuit of Truth.1 I am flattered by his scholarly command of my writings and impressed with his penetration to crucial points. I am thankful, amid all this, for his evidently having missed one vital point in my evolving views; for other readers will have missed it a fortiori, and I am now alerted to make amends for my inadequate exposition. The point he seems to have missed is the preestablished intersubjective harmony of perceptual similarity standards, rooted in natural selection.

Visual stimuli that are made invisible by a following mask can affect overt motor responses and nonmotor processing. Previous studies have compared the effects of primes that were perceptually similar to the subsequent stimulus with those of primes that were perceptually similar to an alternative stimulus. The present study examined the effect of congruent primes that are perceptually dissimilar to the target (or the cue) but are nonetheless associated with the same response (or the same task) as the later stimulus. Positive and inverse priming effects (negative compatibility effects) were studied in a target priming paradigm (Experiments 1 and 2) and in a cue priming paradigm (Experiments 3 and 4). The results showed stronger priming effects with similar primes than with dissimilar congruent primes. However, the effects of perceptually dissimilar congruent primes differed from those of dissimilar incongruent primes. These findings suggest that a substantial part of both positive target and cue priming effects is produced at levels of processing that are not affected by perceptual similarity. The version of inverse priming effects examined in this study, however, seems to arise from perceptual processing that is affected by the similarity between a prime and the stimulus that follows the mask.

We investigated the role of the structure of stimuli and their functional affordance on novel name generalization. Three- and 5-year-old children and adults were shown a training object with two possible functions, each one associated with a different part. They were taught about the name and the function of the object. We compared the classifications obtained for transfer stimuli composed of one part of the training stimulus—functional or not, perceptually transformed or not, or composed of all the original training parts. Even young children generalized the novel name to functional one-part transfer objects and disregarded non-functional or dysfunctional objects, although their generalizations were more constrained by perceptual similarity than that of the adults.

Event-related potentials were used to investigate neural processes relating perceptual similarity to action control. To assess whether perceptual overlap among targets and nontargets would modulate the N2/P3 complex, the present study used multiple nontarget categories varying in their targetlike characteristics. Participants made one (relatively rare) response to a low-probability stimulus (target), and they made a different (relatively common) response to all other stimuli (nontargets). The critical nontarget categories had equivalent probability (.10) but varied in their targetlike characteristics. Supporting the N2 component as sensitive to the strength of conflicting action imperatives, perceptual overlap among targets and nontargets elicited a prominent N2. In contrast, amplitude of the P3 component appeared most sensitive to the extent of cognitive processing needed for categorization.

Two experiments investigated the perceptual generalization of acquisition and extinction in human contingency learning. In Experiment 1, the degree of perceptual similarity between the acquisition stimulus and the generalization stimulus was manipulated over five groups. This successfully generated a generalization gradient of acquisition. In the subsequent phase, the response to the generalization stimulus was extinguished in each group. Finally, the acquisition stimulus was presented again. The response recovered differently over groups, thereby establishing the generalization gradient of extinction. In Experiment 2, the acquisition stimulus itself was extinguished before the set of generalization stimuli was tested between groups. One group evidenced a response recovery at test, which suggests that the gradient of acquisition is somewhat broader than the gradient of extinction.

The identification of the gender of an unfamiliar talker is an easy and automatic process for naïve adult listeners. Sociolinguistic research has consistently revealed gender differences in the production of linguistic variables. Research on the perception of dialect variation, however, has been limited almost exclusively to male talkers. In the present study, naïve participants were asked to categorize unfamiliar talkers by dialect using sentence-length utterances under three presentation conditions: male talkers only, female talkers only, and a mixed gender condition. The results revealed no significant differences in categorization performance across the three presentation conditions. However, a clustering analysis of the listeners’ categorization errors revealed significant effects of talker gender on the underlying perceptual similarity spaces. The present findings suggest that naïve listeners are sensitive to gender differences in speech production and are able to use those differences to reliably categorize unfamiliar male and female talkers by dialect.

The study investigates the perceptual feature similarity between different lexicons based on visual perception of the words and their representation through an observation sequence. We confirm that it is possible to use databases, which are similar in terms of morphological/perceptual features to improve the recognition performance. In this work, we demonstrated through experimentation, that it is possible to improve the recognition rate of handwritten Portuguese words by adding samples of French words in the training set. Experimental results show the efficiency of this strategy reducing the error rate.

The article describes features of trauma memories in post-traumatic stress disorder (PTSD), including characteristics of unintentional re-experiencing symptoms and intentional recall of trauma narratives. Reexperiencing symptoms are usually sensory impressions and emotional responses from the trauma that appear to lack a time perspective and a context. The vast majority of intrusive memories can be interpreted as re-experiencing of warning signals, i.e., stimuli that signalled the onset of the trauma or of moments when the meaning of the event changed for the worse. Triggers of re-experiencing symptoms include stimuli that have perceptual similarity to cues accompanying the traumatic event. Intentional recall of the trauma in PTSD may be characterised by confusion about temporal order, and difficulty in accessing important details, both of which contribute to problematic appraisals. Recall tends to be disjointed. When patients with PTSD deliberately recall the worst moments of the trauma, they often do not access other relevant (usually subsequent) information that would correct impressions/predictions made at the time. A theoretical analysis of re-experiencing symptoms and their triggers is offered, and implications for treatment are discussed. These include the need to actively incorporate updating information ("I know now ...") into the worst moments of the trauma memory, and to train patients to discriminate between the stimuli that were present during the trauma ("then") and the innocuous triggers of re-experiencing symptoms ("now").