Category Boundaries Research Articles

Bayesian average or truncation at boundaries? The mechanisms underlying categorical bias in spatial memory.

Spatial memory is often biased by various factors, such as the region a target belongs to, which can be defined based on physical, perceptual, or implicit boundaries. In the typical dot-localization task first introduced by Huttenlocher, Hedges, and Duncan (Psychological Review 98: 352-376, 1991), individuals normally divide the task space into four quadrants delineated at the Cartesian axes (forming "default categories") and show systematic bias in target localization toward the center of the category. At least two mechanisms have been proposed to account for these categorical biases, namely (a) weighted-average of a metric representation and the category prototype representation and (b)truncation of an un-biased metric representation at the category boundary. Both models can account for these findings and cannot be differentiated by existing research methods. Using a new distribution analysis, the current study sought to differentiate between these two models. Participants viewed a dot inside a circle and recalled its location after a delay either with the same blank circle (i.e., the standard dot-in-circle paradigm) or when an alternative V-shaped category boundary was visually presented at retrieval. The data from three experiments showed symmetrical distribution of the errors that shifted toward the category center when people primarily used the default category, supporting the weighted-average model. In contrast, when people primarily used the alternative category, the errors showed a highly skewed distribution, more consistent with the truncation model. Overall, these results provided the first experimental evidence for both mechanisms separately.

Categorical Perception of Facial Emotions in Infancy.

Categorical perception, indicated by superior discrimination between stimuli that cross categorical boundaries than between stimuli within a category, is an efficient manner of classification. The current study examined the development of categorical perception of emotional stimuli in infancy. We used morphed facial images to investigate whether infants find contrasts between emotional facial images that cross categorical boundaries to be more salient than those that do not, while matching the degree of differences in the two contrasts. Five-month-olds exhibited sensitivity to the categorical boundary between sadness and disgust, between happiness and surprise, as well as between sadness and anger but not between anger and disgust. Even 9-month-olds failed to exhibit evidence of a definitive category boundary between anger and disgust. These findings indicate the presence of discrete boundaries between some, but not all, of the basic emotions early in life. Implications of these findings for the major theories of emotion representation are discussed.

The featuring phenomenon in music: how combining artists of different genres increases a song’s popularity

The appearance of songs including featured artists on Billboard’s Hot 100 music charts has increased exponentially in the past two decades. This particular type of creative collaboration involves one artist integrating another artist’s contribution, either instrumentally or vocally, into their work and publicizing it with a “featuring” credit. According to broad literature in sociology on categorical boundaries, artists who deviate from existing genres are expected to be penalized for violating collective expectations and norms. We find songs featuring other artists actually have a greater likelihood of making it into the top 10 than songs not featuring other artists. Additionally, consistent with theorizing about congruency in the co-branding literature, we observe that the greater the difference (cultural distance) between the genres of the artists involved, the more likely the song is to reach the top of the charts. We argue that by combining the expertise of specialists in each genre, as well as comingling audiences while still maintaining each collaborator’s original positioning, artists who feature artists from other genres are able to produce more successful songs.

Dichotomous perception of animal categories in infancy

ABSTRACTAlthough there is a wealth of knowledge on categorization early in life, there are still many unanswered questions about the nature of category representation in infancy. For example, it is unclear whether infants are sensitive to boundaries between complex categories, such as types of animals, or whether young infants exhibit such sensitivity without explicit experience in the lab. Using a morphing technique, we linearly altered the category composition of images and measured 6.5-month-olds’ attention to pairs of animal faces that either did or did not cross the categorical boundary, with the stimuli in each pair being equally dissimilar from one another across the two types of image pairs. Results indicated that infants dichotomize the continua between cats and dogs and between cows and otters, but only when the images are presented in their canonical, upright orientations. These findings demonstrate a propensity to dichotomize early in life that could have implications for social categorizations, such as race and gender.

The creation of a new vowel category by adult learners after adaptive phonetic training

Native Japanese speakers often perceive English vowels based on their duration, whereas native speakers use spectral cues (formant frequencies). The current study examined whether 23 Japanese adult learners of English could create a new vowel category along the spectral dimension after phonetic training with the English vowels /i/-/ɪ/ as in beat and bit. As in previous training studies, the Japanese trainees improved their ability to categorize the vowels in tokens included in the training, and were able to generalize to novel tokens and talkers. A cue-weighting task confirmed that the Japanese trainees categorized the vowels based on temporal cues before training, presumably because vowel duration is used phonologically in Japanese. While 12 of the Japanese trainees still relied on vowel duration to distinguish the English vowels after training, 11 of them successfully created a new vowel category along the spectral dimension. However, their category boundary between /i/-/ɪ/ was set at a different location from that of native speakers. We interpret these results as providing evidence that it is possible for late inexperienced learners to create new phonetic categories with phonetic training, but that the new categories may be subject to phonetic category dissimilation, an effect previously documented with early bilinguals.

Reassessing the electrophysiological evidence for categorical perception of Mandarin lexical tone: ERP evidence from native and naïve non-native Mandarin listeners.

Some studies have argued that native speakers of tonal languages have been shown to perceive lexical tone continua in a more categorical manner than speakers of non-tonal languages. Among these, Zhang and colleagues (NeuroReport 23 (1): 35-9) conducted an event-related potential (ERP) study using an oddball paradigm showing that native Mandarin speakers exhibit different sensitivity to deviant tones that cross category boundaries compared to deviants that belong to the same category as the standard. Other recent ERP findings examining consonant voicing categories question whether perception is truly categorical. The current study investigated these discrepant findings by replicating and extending the Zhang et al. study. Native Mandarin speakers and naïve English speakers performed an auditory oddball detection test while ERPs were recorded. Naïve English speakers were included to test for language experience effects. We found that Mandarin speakers and English speakers demonstrated qualitatively similar responses, in that both groups showed a larger N2 to the across-category deviant and a larger P3 to the within-category deviant. The N2/P3 pattern also did not differ in scalp topography for the within- versus across-category deviants, as was reported by Zhang et al. Cross-language differences surfaced in behavioral results, where Mandarin speakers showed better discrimination for the across-category deviant, but English speakers showed better discrimination for within-category deviants, though all results were near-ceiling. Our results therefore support models suggesting that listeners remain sensitive to gradient acoustic differences in speech even when they have learned phonological categories along an acoustic dimension.

Innovation or deviation? The relationship between boundary crossing and audience evaluation in the music field

Prior research in organizations has shown that the spanning of distinct social categories usually leads to an unfavorable reaction from the audience. In the music field, however, a recombination of categories has long been celebrated as a major source of innovation. In this research, we conduct a systematical research on the effect of spanning behavior by musicians with a particular focus on the structural heterogeneity of categorical boundaries. We first ask whether the blending of distinct music genres is penalized in the music field, and then investigate how the outcomes of spanning behavior are differentiated by the structural characteristics of each genres. After collecting a comprehensive dataset of musicians in the United States from diverse sources including AllMusic, iTunes, and MusicBrainz, we construct a two-mode network of musicians and subgenres. In calculating musicians’ genre-spanning behavior, we suggest a new diversity metric by incorporating the affinity between genres. Our results suggest that genre-generalist musicians who combine distinct music genres are more likely to be devaluated by listeners compared to genre-specialists who adhere to a single genre. Moreover, we find that musicians tend to be more penalized when they blend genres that have nonporous boundaries rather than penetrable boundaries. This research expands our understanding of the conditions under which boundary crossing leads to negative audience evaluation.

Neural substrates of subphonemic variation and lexical competition in spoken word recognition

ABSTRACTIn spoken word recognition, subphonemic variation influences lexical activation, with sounds near a category boundary increasing phonetic competition as well as lexical competition. The current study investigated the interplay of these factors using a visual world task in which participants were instructed to look at a picture of an auditory target (e.g. peacock). Eyetracking data indicated that participants were slowed when a voiced onset competitor (e.g. beaker) was also displayed, and this effect was amplified when acoustic-phonetic competition was increased. Simultaneously-collected fMRI data showed that several brain regions were sensitive to the presence of the onset competitor, including the supramarginal, middle temporal, and inferior frontal gyri, and functional connectivity analyses revealed that the coordinated activity of left frontal regions depends on both acoustic-phonetic and lexical factors. Taken together, results suggest a role for frontal brain structures in resolving lexical competition, particularly as atypical acoustic-phonetic information maps on to the lexicon.

Humans incorporate attention-dependent uncertainty into perceptual decisions and confidence

Perceptual decisions are better when they take uncertainty into account. Uncertainty arises not only from the properties of sensory input but also from cognitive sources, such as different levels of attention. However, it is unknown whether humans appropriately adjust for such cognitive sources of uncertainty during perceptual decision-making. Here we show that, in a task in which uncertainty is relevant for performance, human categorization and confidence decisions take into account uncertainty related to attention. We manipulated uncertainty in an orientation categorization task from trial to trial using only an attentional cue. The categorization task was designed to disambiguate decision rules that did or did not depend on attention. Using formal model comparison to evaluate decision behavior, we found that category and confidence decision boundaries shifted as a function of attention in an approximately Bayesian fashion. This means that the observer's attentional state on each trial contributed probabilistically to the decision computation. This responsiveness of an observer's decisions to attention-dependent uncertainty should improve perceptual decisions in natural vision, in which attention is unevenly distributed across a scene.

Procedural-Memory, Working-Memory, and Declarative-Memory Skills Are Each Associated With Dimensional Integration in Sound-Category Learning.

This paper investigates relationships between procedural-memory, declarative-memory, and working-memory skills and adult native English speakers’ novel sound-category learning. Participants completed a sound-categorization task that required integrating two dimensions: one native (vowel quality), one non-native (pitch). Similar information-integration category structures in the visual and auditory domains have been shown to be best learned implicitly (e.g., Maddox et al., 2006). Thus, we predicted that individuals with greater procedural-memory capacity would better learn sound categories, because procedural memory appears to support implicit learning of new information and integration of dimensions. Seventy undergraduates were tested across two experiments. Procedural memory was assessed using a linguistic adaptation of the serial-reaction-time task (Misyak et al., 2010a,b). Declarative memory was assessed using the logical-memory subtest of the Wechsler Memory Scale-4th edition (WMS-IV; Wechsler, 2009). Working memory was assessed using an auditory version of the reading-span task (Kane et al., 2004). Experiment 1 revealed contributions of only declarative memory to dimensional integration, which might indicate not enough time or motivation to shift over to a procedural/integrative strategy. Experiment 2 gave twice the speech-sound training, distributed over 2 days, and also attempted to train at the category boundary. As predicted, effects of declarative memory were removed and effects of procedural memory emerged, but, unexpectedly, new effects of working memory surfaced. The results may be compatible with a multiple-systems account in which declarative and working memory facilitate transfer of control to the procedural system.

Contextual Influences on Phonetic Categorization in School-Aged Children.

Perceptual stability in adult listeners is supported by the ability to process acoustic-phonetic variation categorically and dynamically adjust category boundaries given systematic contextual influences. The current study examined the developmental trajectory of such flexibility. Adults and school-aged children (5-10 years of age) made voicing identification decisions to voice-onset-time (VOT) continua that differed in speaking rate and place of articulation. The results showed that both populations were sensitive to contextual influences; the voicing boundary was located at a longer VOT for the slow compared to the fast speaking rate continuum and for the velar compared to the labial continuum, and the magnitude of the displacement was slighter greater for the adults compared to the children. Moreover, the two populations differed in terms of the absolute location of the voicing boundaries and the categorization slopes, with slopes becoming more categorical as age increased. These results demonstrate that sensitivity to contextual influences on speech perception emerges early in development, but mature perceptual tuning requires extended experience.

Estimates of category means are biased away from the category boundary following an orientation-categorization task

Estimates of category means are biased away from the category boundary following an orientation-categorization task

Spectral contrast effects produced by competing speech contexts.

The long-term spectrum of a preceding sentence can alter the perception of a following speech sound in a contrastive manner. This speech context effect contributes to our ability to extract reliable spectral characteristics of the surrounding acoustic environment and to compensate for the voice characteristics of different speakers or spectral colorations in different listening environments to maintain perceptual constancy. The extent to which such effects are mediated by low-level "automatic" processes, or require directed attention, remains unknown. This study investigated spectral context effects by measuring the effects of two competing sentences on the phoneme category boundary between /i/ and /ε/ in a following target word, while directing listeners' attention to one or the other context sentence. Spatial separation of the context sentences was achieved either by presenting them to different ears, or by presenting them to both ears but imposing an interaural time difference (ITD) between the ears. The results confirmed large context effects based on ear of presentation. Smaller effects were observed based on either ITD or attention. The results, combined with predictions from a two-stage model, suggest that ear-specific factors dominate speech context effects but that the effects can be modulated by higher-level features, such as perceived location, and by attention. (PsycINFO Database Record

Linguistic cues are privileged over non-linguistic cues in young children’s categorization

Language affects the way that humans build categories. When two objects share a verbal label, children and adults are encouraged to group them together. In the present study, we offer a stringent test of the potency of labels by comparing them to non-linguistic cues that have been matched in terms of critical properties. In Experiment 1, Four-year-old children were given two categorization tasks with novel natural kinds and artifacts. In both tasks, we compared the effectiveness of novel Labels like zeg and equally discriminable, intentionally introduced patterned Frames. In Experiment 2, we included pretest trials before each of the tasks to ensure children’s awareness of the cues. We observed a pervasive advantage of Labels over Frames in both experiments. Our results offer some of the strongest evidence to date for the conclusion that young children prioritize labels over superficially equipotent non-linguistic cues when drawing category boundaries.

Form Follows Function: An Investigation Into the Categorical Boundary of Surprise.

The concept of basic emotions has been widely accepted in explaining human behavior. Yet, there is still no consensus on the distinctiveness of surprise. This study tried to compare the discreteness of surprise with that of other basic emotions in terms of their categorical distinctiveness. For this study, 27 undergraduates were recruited, and a new set of morphing sequences of different emotional expressions from two young Chinese posers was created. The results show that surprise is over-generalized to the perception of fear and that the categorical boundary is less discrete than for other emotional expression pairs. This blending is perhaps due to their confusion on both the perceptual and production levels. Additionally, a choice between external and internal validity when picking emotional expression stimuli is also discussed.

Use of the STROBE Checklist to Evaluate the Reporting Quality of Observational Research in Obstetrics

To evaluate observational research manuscripts submitted to Obstetrics & Gynecology to determine the level of adherence to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist and highlight specific areas that could be improved. A scoring system based on the STROBE checklist was developed and validated for consistency by volunteer medical students or doctors. Using this scoring system, we performed a cross-sectional analysis on 198 observational research manuscripts submitted to Obstetrics & Gynecology from 2008 to 2016. Each manuscript was given a score based on the STROBE checklist. Comparisons were made among acceptance status, country of origin, and study type. Descriptive statistics (means, medians, and frequencies) were calculated for each manuscript category. The t test or Wilcoxon rank-sum test was used to compare differences between two groups and analysis of variance or the Kruskal-Wallis test was used to compare differences among three or more groups. There was a statistically significant difference between the mean score for accepted (23.2±2.7) compared with rejected (19.7±4.1) manuscripts (P<.001). This difference was not seen when comparing country of origin and study type. Poor reporting was seen among all manuscript categories for objectives, study size, missing data, study participants, and translation of risk. Additionally, rejected manuscripts had poor reporting for eligibility criteria, variables, bias and confounding, statistical methods, unadjusted and adjusted estimates, and category boundaries. Overall, accepted manuscripts show better adherence to the STROBE checklist, but there are several critical items that are poorly reported in all manuscripts.

Categorical perception of colour signals in a songbird.

In many contexts, animals assess each other using signals that vary continuously across individuals and, on average, reflect variation in the quality of the signaller1,2. It is often assumed that signal receivers perceive and respond continuously to continuous variation in the signal2. Alternatively, perception and response may be discontinuous3, owing to limitations in discrimination, categorization or both. Discrimination is the ability to tell two stimuli apart (for example, whether one can tell apart colours close to each other in hue). Categorization concerns whether stimuli are grouped based on similarities (for example, identifying colours with qualitative similarities in hue as similar even if they can be distinguished)4. Categorical perception is a mechanism by which perceptual systems categorize continuously varying stimuli, making specific predictions about discrimination relative to category boundaries. Here we show that female zebra finches (Taeniopygia guttata) categorically perceive a continuously variable assessment signal: the orange to red spectrum of male beak colour. Both predictions of categorical perception5 were supported: females (1) categorized colour stimuli that varied along a continuum and (2) showed increased discrimination between colours from opposite sides of a category boundary compared to equally different colours from within a category. To our knowledge, this is the first demonstration of categorical perception of signal-based colouration in a bird, with implications for understanding avian colour perception and signal evolution in general.

Boundary Kinking in Public Grading Schemes: The Effects of Tie Strength in Social Relationships

Discontinuities frequently appear in the distribution of scores underlying the grades of public regulation schemes such as restaurant hygiene inspections. The typical study of such discontinuities conceives of them as representing rational behavioral responses to incentives inherent in the scheme itself. By contrast, we study how the evolving social relationships between inspectors and restaurants influence grading outcomes in a systematic manner. We study 512,313 inspections in Los Angeles County between 2000 and 2010, conducted by 606 inspectors in 29,666 restaurants. We find that the stronger the social tie between an inspector and a restaurateur, the more likely the inspector will be to “fudge” upward the inspection score. When aggregated, this behavior produces discontinuities – or kinks – in the distribution of scores occurring around the grade category boundaries. This behavior appears to be part of an implicit quid pro quo agreement: a lenient inspection in exchange for the restaurateur not requesting a re-examination. Importantly, the behavior generates public costs: restaurants that enjoy stronger social ties with inspectors are subsequently more likely to receive a customer complaint. These findings offer insight into how commensuration operates in the context of public grading schemes and point to a range of implications for sociological theory.

A Graded Response Model Framework for Questionnaires With Uniform Response Formats.

Questionnaires with uniform-ordered categorical response formats are widely applied in psychology. Muraki proposed a modified graded response model accounting for the items' uniform response formats by assuming identical threshold parameters defining the category boundaries for all items. What is not well known is that there is a set of closely related models, which similarly assume identical thresholds. The present article gives a framework illustrating the differences between these models and their utility for understanding questionnaire responses in detail. The models are explained as constrained cases of a one-dimensional factor model for ordered categorical data. Furthermore, the authors show that the models can be written and fitted as structural equation models, which allows for a very flexible and general purpose use. Instructions on implementing the models in Mplus and SAS PROC NLMIXED are given.

Toward a Strategic Perspective on Categorization

Existing research believes that the categorization process is exogenous, and penalties arise when organizations attempt to straddle categories. However, category spanners are widely seen in modern society, implying that unidentified mechanisms may trigger organizations to cross category boundaries. I hence argue that the categorization process is endogenous to organizations to some extent, and internal organizational agents play an important role in shaping the category domain the focal organization claims in. Using a large dataset from online film databases, I study the categorization of feature films in North America. I find that the team- and personal- level attributes of a film crew, including the producer, director, and casts, deeply affect the genre labels the focal film will receive from audiences. In addition, the extent to which the film crew interferes in the categorization process ultimately affects the box office gross of the focal film. My research advances category research by framing categorization as a producer-centric, rather than an audience-centric, process, and recognizing the role of organizational agents in product categorization.