Relationship between uniform connectedness and proximity in perceptual grouping

1 Introduction The visual world is composed of complex visual scenes that are projected, as two-dimen- sional images, onto the retina. Chunking of visual information is critical for object recognition, because it produces primitive perceptual units for subsequent analyses[1]. Integration of discrete local elements into a global configuration is one of the functions of perceptual grouping (e.g., combining local rectangles into a global letter as shown in fig. 1(b)). When multiple global object…     

Perceptual organization at attended and unattended locations

This study examined the effects of attention on forming perceptual units by proximity grouping and by uniform connectedness (UC). In Experiment 1 a row of three global letters defined by either proximity or UC was presented at the center of the visual field. Participants were asked to identify the letter in the middle of stimulus arrays while ignoring the flankers. The stimulus onset asynchrony (SOA) between stimulus arrays and masks varied between 180 and 500 ms. We found that responses to targets defined by proximity grouping were slower than to those defined by UC at median SOAs but there were no differences at short or long SOAs. Incongruent flankers slowed responses to targets and this flanker compatibility effect was larger for UC than for proximity-defined flankers. Experiment 2 examined the effects of spatial precueing on discrimination responses to proximity- and UC-defined targets. The advantage for targets defined by UC over targets defined by proximity grouping was greater at uncued relative to cued locations. The results suggest that the advantage for UC over proximity grouping in forming perceptual units is contingent on the stimuli not being fully attended, and that paying attention to the stimuli differentially benefits proximity grouping.     

Perceptual organization at attended and unattended locations

In order to perceive complex visual scenes, the human perceptual system has to organize discrete enti-ties in the visual field into chunks or perceptual units for higher-level processing. Perceptual organization is governed by Gestalt principles such as proximity, similarity, and continuity[1]. Thus spatially close ob-jects tend to be grouped together, as do elements that are similar to one another. Grouping based on the Ge-stalt laws (particularly proximity) is critical for the perception of…     

前颞叶在知觉组织中的作用：脑损伤病人的神经心理学研究

相邻性组织和相似性组织是两种极为重要的“知觉组织(perceptual organization)”．我们对前颞叶切除的患者CXY进行了相邻性组织与相似性组织的研究．利用由小图形组成的大图形来研究在相邻性组织与相似性组织中整体与局部之间的相互影响．研究中发现：在相邻性组织中,正常被试所体现的整体对局部的影响显著大于局部对整体的影响这一现象在CXY身上消失了,即CXY相邻性组织的自动加工出现了障碍;在相似性组织中,患者CXY的实验结果与正常被试没有任何差异．另外,在一致连通性(uniform connectedness, UC) 与相邻性组织及相似性组织之间的关系实验中,也发现CXY相邻性组织的自动加工出现了障碍．这些结果说明左前颞叶在相邻性组织、整体知觉以及对连通性的知觉中起到重要的作用．     

Evaluation of connectedness between herds for three pig breeds in China

Using data on age at 100 kg of three pig breeds (Large White, Landrace and Duroc) the connectedness between herds in China was evaluated by the connectedness rating (CR) method. The results show that most herds in China have low average CR (0-3.59%) with other herds. In Large White, of the 36 herds analyzed there are 20 herds, which are connected with at least one other herd. In Landrace and Duroc, of the 27 and 18 herds analyzed, only four and five herds, respectively, were found having connectedness with other herds. Generally, the connectedness exists only among two or few herds in the same region. A certain degree of connectedness between herds is a precondition for cross-herd genetic evaluation. A national or regional cross-herd genetic evaluation is not practicable at the present time in China. More intense efforts are needed to establish and enhance the connectedness between herds by means of extensively using artificial insemination (AI) in the swine industry in China.     

Perception and apperception in autism: rejecting the inverse assumption

In addition to those with savant skills, many individuals with autism spectrum conditions (ASCs) show superior perceptual and attentional skills relative to the general population. These superior skills and savant abilities raise important theoretical questions, including whether they develop as compensations for other underdeveloped cognitive mechanisms, and whether one skill is inversely related to another weakness via a common underlying neurocognitive mechanism. We discuss studies of perception and visual processing that show that this inverse hypothesis rarely holds true. Instead, they suggest that enhanced performance is not always accompanied by a complementary deficit and that there are undeniable difficulties in some aspects of perception that are not related to compensating strengths. Our discussion emphasizes the qualitative differences in perceptual processing revealed in these studies between individuals with and without ASCs. We argue that this research is important not only in furthering our understanding of the nature of the qualitative differences in perceptual processing in ASCs, but can also be used to highlight to society at large the exceptional skills and talent that individuals with ASCs are able to contribute in domains such as engineering, computing and mathematics that are highly valued in industry.     

Influences of parasites and thermoregulation on grouping tendencies in marine iguanas

I determined whether grouping behavior influences parasite loadand body temperature of Galápagos marine iguanas, reptilesthat rest gregariously. Mobile (or predatory) Ornithodoros ticks(4.7 mm average body length) approached at a ground speed of65 cm/min and parasitized sleeping marine iguanas for 3.7 hper night, drawing about 0.1 ml blood. Contagiously transmittedAmblyomma ticks hang on to iguana hosts for days or weeks. Marineiguanas sleeping alone had 2.0 mobile ticks per night, whileindividuals sleeping in groups had 0.1 to 1.1 mobile ticks pernight. Single iguanas decreased their mobile parasite load to0.2 ticks per night by sleeping on bushes. Experimental nightlytranslocation of iguanas to areas without other sleeping iguanassignificantly increased their mobile parasite burden above levelsencountered by naturally single individuals (n = 4.6 ticks pernight). Creating an experimental group of two animals reducedinfestation with mobile ticks by 59% compared to levels on singleanimals. Over the course of weeks, mobile ectoparasite loadsat grouping sites increased to levels found at single sites,at which point marine iguanas changed sleeping sites. Groupinghad no effect on the prevalence of contagious ticks. Furthermore,grouping did not help to conserve body temperature in Genovesaiguanas, as measured by radiotelemetry. I conclude that marineiguanas group during daytime at microhabitats favored for thermoregulation(predation is absent in this population). Thermoregulation wasnot of prime importance for nightly aggregations, which insteadserved to reduce mobile ectoparasite load. As a minimum costof infestation, I estimate that individuals sleeping alone wouldhave a 5.4% lower annual energy budget due to tissue removal,not including potential internal infections.     

Evidence for deficiencies in perceptual and semantic olfactory processes in Parkinson's disease

Olfactory deficits have been reported in Parkinson's disease (PD) and are thought to represent a sensitive marker of the disease. The aim of the present study was to examine the differential contribution in olfactory dysfunction of perceptual and semantic processes of odours in PD patients. Twenty-four PD patients (12 males and 12 females) and 24 control subjects (12 males and 12 females) were tested. The experiment included two sessions. Initially, 12 odorants were delivered, one per minute. For each odour, subjects were asked to rate intensity, pleasantness, familiarity and edibility using linear rating scales. The odorants were again presented and the subjects were asked to identify them. The four olfactory judgements and odour identification were severely disturbed in PD patients when compared to control subjects. These findings demonstrate major deficits for all cognitive tasks of olfactory judgement in PD, and suggest that PD is associated with disruption of olfactory areas situated in the temporal lobes and also in the prefrontal cortex.     

Reciprocity in play,grooming, and proximity in sibling and nonsibling young rhesus monkeys

Play, grooming, and proximity, and the degree to which these were reciprocated between pairs, were studied in immature sibling and nonsibling rhesus monkeys (Macaca mulatta)in four established captive groups over two seasons. “Interaction reciprocity” and “partner reciprocity” were assessed for each dyad for each of the three behaviors. In play, interaction reciprocity was based on the ratio between the play initiations by each dyad member,in grooming on the ratio between the grooming durations by each dyad member, and in proximity on the relative responsibility for proximity maintenance. Two or three most frequent (top) partners for each behavior were found for each individual. If two monkeys were among each other’s top partners, they were said to be reciprocal partners. Monkeys played with nonsiblings as much as with siblings but spent more time grooming and in proximity with siblings than with nonsiblings. Same-age nonsiblings (peers) were more frequent partners than other nonsiblings for each behavior. Siblings’ grooming interactions were more reciprocal than those of nonsiblings. There was no such effect for play and proximity. All-male dyads tended to be more reciprocal in play interactions, and all-female dyads tended to be more reciprocal in grooming interactions. In play, but not in grooming or proximity, the interaction reciprocity of reciprocal partners was higher than that of nonreciprocal dyads. It is argued that the three behaviors have similar roles in infant’s social development but they differ in the expression of this role. Hence the reciprocity patterns vary with the behavior.     

Effects of proximity and activity on visual and auditory monitoring in wild Japanese macaques

Group-living primates monitor group members to maintain the spatial cohesiveness of the group. We examined the possibility that visual scanning (turning the head for more than 3 sec) and contact calls (coo calls) function as visual and auditory monitoring behaviors to avoid separation from group members in wild Japanese macaques. The rate of visual scanning increased as proximity to group members decreased and as mobile activities (foraging and moving) increased, compared with immobile activities (resting and grooming). However, the rate of contact calls varied differently with proximity and activities. During resting and moving, the rate of contact calls increased as proximity decreased. In contrast, the rate increased with closer proximity during feeding. Visual scanning during all activities and contact calls during resting and moving increased when the group members were likely to spread over a larger area, suggesting that these behaviors functioned as monitoring of group members to avoid separation from the group. Contact calls also increased when the group members stayed in close proximity during foraging, suggesting that this behavior was also associated with competitive situations. Contact calls may also function to ease tension or maintain distance to avoid conflict in competitive situations.     

Effects of food,proximity, and kinship on social behavior in ringtailed lemurs

Efforts to understand the variation in primate social systems and their underlying interaction patterns have focused on both intrinsic and extrinsic factors. In the socioecological model, food distribution and abundance have been argued to be the primary influences on the social behavior of primate species. We examined the relationship of food resources and two intrinsic factors—kinship and proximity—with patterns of affiliative and agonistic relationships in two semi‐free ranging ringtailed lemur, Lemur catta, social groups (N=14) at The Duke Lemur Center in Durham, NC. In analyzing these three factors concurrently within the same system, we attempt to establish their relative power in explaining the characteristics of social relationships. Patterns of affiliation and high‐intensity agonism were best explained by kinship. Proximity also explained affiliation but did not explain agonism, which varied considerably between groups. The influence of food on social interactions was highly variable between the two groups and, therefore, did not convincingly account for the social behavior patterns we observed. Finally, different intensities of agonism have different patterns and should be analyzed individually. The variation between social groups makes it difficult for us to conclude that any one factor is primarily and universally responsible for patterns of social behavior in this species. Am. J. Primatol. 72:981–991, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of proximity and behavioral context on acoustic variation in the coo calls of Japanese macaques

Acoustic features of coo calls in Japanese macaques (Macaca fuscata) show large and graded variation. To explore the relevance of acoustic variation in coo calls, I examined whether acoustic features differed by the caller's activity and proximity to group members. The subjects were five adult females from a wild, habituated group of Japanese macaques consisting of 23 individuals. Coo calls from the five females were recorded with their activity and proximity to group members. Acoustic features of 280 calls were measured with a sound spectrograph. Some of the acoustic variables differed by proximity but not by activity. The callers produced coo calls with larger frequency modulation and longer duration when they were far from group members compared to when they were near another member. The results suggest that Japanese macaques produce calls with more detectable and locatable features depending on the proximity to group members.     

The relationship between visual working memory and attention: retention of precise colour information in the absence of effects on perceptual selection

We examined the conditions under which a feature value in visual working memory (VWM) recruits visual attention to matching stimuli. Previous work has suggested that VWM supports two qualitatively different states of representation: an active state that interacts with perceptual selection and a passive (or accessory) state that does not. An alternative hypothesis is that VWM supports a single form of representation, with the precision of feature memory controlling whether or not the representation interacts with perceptual selection. The results of three experiments supported the dual-state hypothesis. We established conditions under which participants retained a relatively precise representation of a parcticular colour. If the colour was immediately task relevant, it reliably recruited attention to matching stimuli. However, if the colour was not immediately task relevant, it failed to interact with perceptual selection. Feature maintenance in VWM is not necessarily equivalent with feature-based attentional selection.     

Relationship between song characters and morphology in New World pigeons

We studied the pattern of variation in song characters among 16 New World pigeon species belonging to different taxonomic groups defined by morphological characters. Structural, temporal and frequency characters of the song were analysed. Principal components analyses showed that species belonging to the same taxonomic group were also grouped together by their song characters. In addition, individuals were correctly assigned into taxonomic groups by discriminant function analyses in more than 87.8% of cases. These analyses also showed that more than 87.5% of the individuals could be correctly classified by species when all song characters were included. Correct classification of individuals by species and taxonomic groups dropped when character types were analysed separately, thus showing that structural, as well as temporal and frequency characters are fundamental to define species- and group-specific identities of New World pigeon's songs. Correspondence between patterns of vocal and morphological variation found in this study can be a consequence of evolutionary changes in morphology affecting song production, as for example body size changes that constrain the syrinx to produce certain acoustic frequencies.     

Vigilance and grouping in the southern African ground squirrel (Xerus inauris)

Animals may form groups in response to the foraging–vigilance trade‐off, through enhanced predator detection (collective detection hypothesis) or reduced predation risk to the individual (dilution hypothesis), allowing individuals to decrease vigilance levels. Both hypotheses predict decreasing individual vigilance levels with increasing group size; however, the collective detection hypothesis also predicts increasing overall group vigilance with increasing group size. However, in species in which vigilance and foraging are not mutually exclusive, where vigilance may not be as costly, neither of these hypotheses may apply. Here, we examine the relationship between group size and vigilance in the social Cape ground squirrel (Xerus inauris), a species that can combine foraging and vigilance behaviours. Ten groups were observed using scan sampling, measuring both group and individual vigilance and group size. A negative relationship existed between individual vigilance and group size and a positive relationship between group vigilance and group size. Therefore, in Cape ground squirrels, vigilance seems to be costly even though it can be combined with foraging behaviours. Furthermore, group vigilance behaviour gives support to the collective detection hypothesis, whilst individual vigilance gives support to both hypotheses.     

A novel cell-based scintillation proximity assay for studying protein function and activity in vitro using membrane-soluble scintillants

Here we describe for the first time a cell-based scintillation proximity assay using membrane soluble scintillants (MSS). MSS have a scintillant "head" group (2,5-diphenyloxazole) attached to a lipophilic "tail." MSS do not scintillate in an aqueous environment in the presence of a radioactive source: however, in a non-aqueous environment, such as a lipid bilayer (e.g., liposome or cell membrane), scintillation does occur. MSS can be incorporated into liposomes. When these MSS-containing liposomes are fused with the plasma membranes of cells in culture the MSS are incorporated into the cell membrane. Radiolabelled molecules in close proximity to the cell membrane will then elicit a scintillation signal. This system has been used to successfully monitor [(14)C]methionine uptake in HeLa cells and may be used in radiochemical and radioligand binding assays either in vivo or on microsomal preparations obtained from tissues. This new scintillation proximity technology could be readily adapted for high-throughput screening.     

Soil formation and grouping of soils of the taiga zone in central West Siberia

Natural environments of the taiga zone in central West Siberia have been analyzed, with emphasis placed on the geological and morphological structure of the territory and morphology of soils. The main factors of soil formation are recognized, the main processes of soil formation are revealed, and a systematic list of soil kinds is compiled.     

青檀SRAP-PCR体系优化设计方案

以青檀(Pteroceltis tatarinowii Maxim.)叶片为材料,采用正交设计和均匀设计两种方法对SRAP-PCR反应体系进行优化,并对这两种设计方案优化出的最佳反应体系进行比较,结果表明:两种设计均可用于青檀SRAP-PCR体系的优化,但与正交设计相比,均匀设计在多因素多水平条件下,得到的条带更清晰、稳定性更好。通过实验比较筛选出的青檀SRAP-PCR最佳反应体系为:2.5μL 10×PCR buffer,20 ng模板DNA,Mg2+2.5 mmol/L,dNTP150μmol/L,引物0.2μmol/L,Taq DNA聚合酶1.0 U,总体积25μL。     

Spatial relationships between mate acquisition probability and aggregation size in a gregarious coreid bug, (Colpula lativentris): A case of the ideal free distribution under perceptual constraints

Spatial relationships of mate acquisition probability for individuals of both sexes of a gregariously-mating coreid bug, Colpula lativentris, were studied in relation to aggregation size. Operational sex ratio was always strongly male biased. Mate acquisition probability of females was rather constant and independent of aggregation size, as predicted by an ideal free distribution. Moreover laboratory experiments showed that both multiple mating and rearing density little affected female fecundity, suggesting ideal free distribution of females in terms of reproductive success. On the other hand, mate acquisition probability of males was higher in larger aggregations, where more receptive females were available. This male discrepancy from an ideal free distribution was similar to the patterns predicted by an ideal free distribution under perceptual constraints (Abrahams, 1986), but not by that under unequal competitive ability.     

Molecular dynamics simulations of a protein model in uniform and elongational flows

We present a molecular dynamics study of the conformational deformation of a minimalist beta-barrel protein model in two different types of hydrodynamic flows: uniform and elongational. We investigate the characteristics of protein stretching, paying special attention to the unfolding intermediate states and their relationship to the protein folding/unfolding problem. In the uniform flow simulations, one end of the modeled protein was tethered to a fixed point in space and the forced unfolding process was observed. The unfolding takes place via a few stages involving one or two intermediate states, depending on which end is tethered. The calculated force-extension curves show plateau regimes and hysteresis as the protein is stretched and refolded, in qualitative agreement with the experimental measurements. The physical behavior observed in our numerical simulations of the forced unfolding in an elongational flow is very different from that in uniform flow. The protein unfolds abruptly from the globular state to a fully stretched state without going through any observable intermediate states. From these observation, we stress that protein unfolding pathways under the influence of an external force are highly dependent on the mechanism of the exerted force.