MATCHING THE SHAPE OF TIME-INTENSITY CURVES1

Time-Intensity Curves are often summarized by average curves. From these curves TI-parameters are inferred. In this paper a different method is proposed in which the shape of the curves is the central concept. Isotropic scaling factors are computed for each curve. These factors can be tabled and inspected. Often a large number of scaling factors will be computed, which makes it hard to study them in a table. In such cases they can be represented in a plot, for which in this paper PCA is suggested. In this plot a structure in the scaling factors for the different TI-curves may become visible. It is also possible to make a plot in which the homogeneity of the panel of subjects can be studied.     

Dogs' Social Referencing towards Owners and Strangers

Social referencing is a process whereby an individual uses the emotional information provided by an informant about a novel object/stimulus to guide his/her own future behaviour towards it. In this study adult dogs were tested in a social referencing paradigm involving a potentially scary object with either their owner or a stranger acting as the informant and delivering either a positive or negative emotional message. The aim was to evaluate the influence of the informant''s identity on the dogs'' referential looking behaviour and behavioural regulation when the message was delivered using only vocal and facial emotional expressions. Results show that most dogs looked referentially at the informant, regardless of his/her identity. Furthermore, when the owner acted as the informant dogs that received a positive emotional message changed their behaviour, looking at him/her more often and spending more time approaching the object and close to it; conversely, dogs that were given a negative message took longer to approach the object and to interact with it. Fewer differences in the dog''s behaviour emerged when the informant was the stranger, suggesting that the dog-informant relationship may influence the dog''s behavioural regulation. Results are discussed in relation to studies on human-dog communication, attachment, mood modification and joint attention.     

Lifting without Seeing: The Role of Vision in Perceiving and Acting upon the Size Weight Illusion

Background

Our expectations of an object''s heaviness not only drive our fingertip forces, but also our perception of heaviness. This effect is highlighted by the classic size-weight illusion (SWI), where different-sized objects of identical mass feel different weights. Here, we examined whether these expectations are sufficient to induce the SWI in a single wooden cube when lifted without visual feedback, by varying the size of the object seen prior to the lift.

Methodology/Principal Findings

Participants, who believed that they were lifting the same object that they had just seen, reported that the weight of the single, standard-sized cube that they lifted on every trial varied as a function of the size of object they had just seen. Seeing the small object before the lift made the cube feel heavier than it did after seeing the large object. These expectations also affected the fingertip forces that were used to lift the object when vision was not permitted. The expectation-driven errors made in early trials were not corrected with repeated lifting, and participants failed to adapt their grip and load forces from the expected weight to the object''s actual mass in the same way that they could when lifting with vision.

Conclusions/Significance

Vision appears to be crucial for the detection, and subsequent correction, of the ostensibly non-visual grip and load force errors that are a common feature of this type of object interaction. Expectations of heaviness are not only powerful enough to alter the perception of a single object''s weight, but also continually drive the forces we use to lift the object when vision is unavailable.     

A COMPARISON OF METHODS FOR MONITORING INDIVIDUAL PERFORMANCES IN TASTE SELECTION TESTS

The evaluation of panel performance was made by three methods: average of correct responses (A), comparison of distances of individual standardized judgments to the average standardized responses (D) and a principal components analysis (PCA). Thirty assessors identified water and basic tastes and discriminated different sweet stimuli in neutral or acidified vehicles using R‐index rating and ranking tests. By A and D methods 22 assessors were qualified as proficient. Composition of both panels was identical except for one judge. The output from PCA provided a graphical representation of the performance of the assessors and retained different subsets of 24–26 panelists for different proposals as discrimination of sweetness in acidified beverages, recognition of bitterness, sourness and discrimination of slight sweetness or evaluation of saltiness.     

How objects are grasped: the interplay between affordances and end-goals

Background

Substantial literature has demonstrated that how the hand approaches an object depends on the manipulative action that will follow object contact. Little is known about how the placement of individual fingers on objects is affected by the end-goal of the action.

Methodology/Principal Findings

Hand movement kinematics were measured during reaching for and grasping movements towards two objects (stimuli): a bottle with an ordinary cylindrical shape and a bottle with a concave constriction. The effects of the stimuli''s weight (half full or completely full of water) and the end-goals (pouring, moving) of the action were also assessed. Analysis of key kinematic landmarks measured during reaching movements indicate that object affordance facilitates the end-goal of the action regardless of accuracy constraints. Furthermore, the placement of individual digits at contact is modulated by the shape of the object and the end-goal of the action.

Conclusions/Significance

These findings offer a substantial contribution to the current debate about the role played by affordances and end-goals in determining the structure of reach-to-grasp movements.     

Perceived object stability depends on multisensory estimates of gravity

Background

How does the brain estimate object stability? Objects fall over when the gravity-projected centre-of-mass lies outside the point or area of support. To estimate an object''s stability visually, the brain must integrate information across the shape and compare its orientation to gravity. When observers lie on their sides, gravity is perceived as tilted toward body orientation, consistent with a representation of gravity derived from multisensory information. We exploited this to test whether vestibular and kinesthetic information affect this visual task or whether the brain estimates object stability solely from visual information.

Methodology/Principal Findings

In three body orientations, participants viewed images of objects close to a table edge. We measured the critical angle at which each object appeared equally likely to fall over or right itself. Perceived gravity was measured using the subjective visual vertical. The results show that the perceived critical angle was significantly biased in the same direction as the subjective visual vertical (i.e., towards the multisensory estimate of gravity).

Conclusions/Significance

Our results rule out a general explanation that the brain depends solely on visual heuristics and assumptions about object stability. Instead, they suggest that multisensory estimates of gravity govern the perceived stability of objects, resulting in objects appearing more stable than they are when the head is tilted in the same direction in which they fall.     

The Conforming Brain and Deontological Resolve

Our personal values are subject to forces of social influence. Deontological resolve captures how strongly one relies on absolute rules of right and wrong in the representation of one''s personal values and may predict willingness to modify one''s values in the presence of social influence. Using fMRI, we found that a neurobiological metric for deontological resolve based on relative activity in the ventrolateral prefrontal cortex (VLPFC) during the passive processing of sacred values predicted individual differences in conformity. Individuals with stronger deontological resolve, as measured by greater VLPFC activity, displayed lower levels of conformity. We also tested whether responsiveness to social reward, as measured by ventral striatal activity during social feedback, predicted variability in conformist behavior across individuals but found no significant relationship. From these results we conclude that unwillingness to conform to others'' values is associated with a strong neurobiological representation of social rules.     

The role of prefrontal cortex in working memory: examining the contents of consciousness.

Working memory enables us to hold in our ''mind''s eye'' the contents of our conscious awareness, even in the absence of sensory input, by maintaining an active representation of information for a brief period of time. In this review we consider the functional organization of the prefrontal cortex and its role in this cognitive process. First, we present evidence from brain-imaging studies that prefrontal cortex shows sustained activity during the delay period of visual working memory tasks, indicating that this cortex maintains on-line representations of stimuli after they are removed from view. We then present evidence for domain specificity within frontal cortex based on the type of information, with object working memory mediated by more ventral frontal regions and spatial working memory mediated by more dorsal frontal regions. We also propose that a second dimension for domain specificity within prefrontal cortex might exist for object working memory on the basis of the type of representation, with analytic representations maintained preferentially in the left hemisphere and image-based representations maintained preferentially in the right hemisphere. Furthermore, we discuss the possibility that there are prefrontal areas brought into play during the monitoring and manipulation of information in working memory in addition to those engaged during the maintenance of this information. Finally, we consider the relationship of prefrontal areas important for working memory, both to posterior visual processing areas and to prefrontal areas associated with long-term memory.     

Attribute Pair-Based Visual Recognition and Memory

Background

In the human visual system, different attributes of an object, such as shape, color, and motion, are processed separately in different areas of the brain. This raises a fundamental question of how are these attributes integrated to produce a unified perception and a specific response. This “binding problem” is computationally difficult because all attributes are assumed to be bound together to form a single object representation. However, there is no firm evidence to confirm that such representations exist for general objects.

Methodology/Principal Findings

Here we propose a paired-attribute model in which cognitive processes are based on multiple representations of paired attributes. In line with the model''s prediction, we found that multiattribute stimuli can produce an illusory perception of a multiattribute object arising from erroneous integration of attribute pairs, implying that object recognition is based on parallel perception of paired attributes. Moreover, in a change-detection task, a feature change in a single attribute frequently caused an illusory perception of change in another attribute, suggesting that multiple pairs of attributes are stored in memory.

Conclusions/Significance

The paired-attribute model can account for some novel illusions and controversial findings on binocular rivalry and short-term memory. Our results suggest that many cognitive processes are performed at the level of paired attributes rather than integrated objects, which greatly facilitates the binding problem and provides simpler solutions for it.     

Species performances and vegetation boundaries along an environmental gradient

A transect in grassland vegetation in the southern part of the Netherlands showing both a very gradual and a more marked transition in species composition, was sampled as regards species frequency and a number of soil variables. Clustering (TABORD) and Principal Component Analysis revealed the two types of vegetation boundaries, a strong, rigid and a weak, gradual boundary, and the gradient situation in the transect. Species performance curves were tested for Gaussian form, but less than half of the species showed this form even though limits for acceptance were mild. The few species showing a Gaussian response curve clearly illustrate the two types of vegetation boundaries in this transect in agreement with Whittaker's model for such boundaries.     

Perception of Elasticity in the Kinetic Illusory Object with Phase Differences in Inducer Motion

Background

It is known that subjective contours are perceived even when a figure involves motion. However, whether this includes the perception of rigidity or deformation of an illusory surface remains unknown. In particular, since most visual stimuli used in previous studies were generated in order to induce illusory rigid objects, the potential perception of material properties such as rigidity or elasticity in these illusory surfaces has not been examined. Here, we elucidate whether the magnitude of phase difference in oscillation influences the visual impressions of an object''s elasticity (Experiment 1) and identify whether such elasticity perceptions are accompanied by the shape of the subjective contours, which can be assumed to be strongly correlated with the perception of rigidity (Experiment 2).

Methodology/Principal Findings

In Experiment 1, the phase differences in the oscillating motion of inducers were controlled to investigate whether they influenced the visual impression of an illusory object''s elasticity. The results demonstrated that the impression of the elasticity of an illusory surface with subjective contours was systematically flipped with the degree of phase difference. In Experiment 2, we examined whether the subjective contours of a perceived object appeared linear or curved using multi-dimensional scaling analysis. The results indicated that the contours of a moving illusory object were perceived as more curved than linear in all phase-difference conditions.

Conclusions/Significance

These findings suggest that the phase difference in an object''s motion is a significant factor in the material perception of motion-related elasticity.     

Individual and Sex Differences in Habituation and Neophobia in House Sparrows (Passer domesticus)

Heterogeneity in the environment favours foragers that are flexible (phenotypically plastic). However, consistent individual differences in behaviour (personality), such as in risk‐taking, might affect an individual's ability to find food, avoid predators and adjust to new conditions. It is now well known that personalities exist in many taxa, but much less is known about individual variation in plasticity. We measured the tendency to begin foraging across different levels of risk in house sparrows (Passer domesticus), using a behavioural reaction norm framework to simultaneously assess personality and plasticity. We asked whether individuals were consistently different across risk levels, and whether they differed in habituation and neophobia, both of which were treated as cases of plasticity. We found that males habituated more than females by beginning to feed sooner after repeated instances of a human disturbance in the presence of an initially unfamiliar object. Individuals of both sexes also exhibited consistent differences across trials, but did not differ in the rate of habituation beyond the difference between the sexes. When a novel object was placed in the foraging area, both sexes exhibited similar degrees of neophobia by delaying feeding. The magnitude of this change varied among birds, indicating individual differences in neophobia. Our results indicate that both personality and individual variation in plasticity exist but should be treated as independent phenomena. The presence of variation in plasticity implies that the raw material necessary for selection on neophobia exists, and that if heritable, plasticity in risk‐taking across contexts could evolve.     

Measures of individual differences in taste and creaminess perception

Previous reports that the sensitivity to the bitter tasting substance 6-n-propylthiouracil (PROP) is related to the sensitivity to other tastes, to chemical irritants, and to fats and oils have led to adoption of PROP as a measure of general oral sensitivity and as a predictor of dietary habits that could impact health. The results, however, have not been consistent. It was recently discovered that the ability to perceive "thermal taste" (i.e., sweetness from thermal stimulation alone) was associated with higher responsiveness to 4 prototypical taste stimuli but not to PROP. This finding implied that individual differences in taste perception are determined in large part by factors other than those related to genetic expression of the PROP receptor. The present study followed up this observation by comparing individual differences in perception of 4 prototypical taste stimuli (sucrose, NaCl, citric acid, and quinine) and PROP under conditions that also enabled assessment of the reliability of individual intensity ratings of taste. Creaminess ratings of 3 milk products that had different fat contents were also collected to investigate further the relationship between taste and oral somatosensory perception. The results showed that intensity ratings across 2 trials were significantly correlated for all 5 taste stimuli and that averaging across replicates led to significant correlations among the 4 prototypical stimuli. In contrast, the bitterness of PROP was correlated only with the bitterness of quinine. None of the taste stimuli, including PROP, was significantly correlated with ratings of creaminess. These results imply 1) that with the exception of PROP, as few as 2 intensity ratings of common taste stimuli can reveal individual differences in overall taste perception and 2) that any relationship between taste and oral sensation is too weak to be detected under the same conditions. Accordingly, the results support other evidence that the genetic factors which determine the ability to perceive PROP do not play a major role in overall taste and oral somatosensory perception.     

Shyness–Boldness,but not Exploration,Predicts Glucocorticoid Stress Response in Richardson's Ground Squirrels (Urocitellus richardsonii)

The relationship between stress and personality has often been studied using captive animals in a laboratory context, yet less often in wild populations. Wild populations, however, may reveal aspects of the personality–stress relationship that laboratory‐based studies cannot. Here, we assessed the personality and stress hormone response of adult females within a free‐living population of Richardson's ground squirrels (Urocitellus richardsonii). Personality was assessed by quantifying individual responses to a novel object, and physiological stress was measured from faecal glucocorticoid metabolites. Principal component and principal component regression analyses were performed to determine whether the behavioural and endocrine measures were related. Based on these analyses, shyness–boldness was found to best predict glucocorticoid levels, in that individuals expressing the greatest vigilance in response to the novel object also had the highest measured concentrations of faecal glucocorticoids. Exploration, however, was independent of measured glucocorticoid levels, consistent with a multidimensional interpretation of non‐human animal personality.     

The Mental Representation of Social Connections: Generalizability Extended to Beijing Adults

Social connections are essential for the survival of a social species like humans. People differ in the degree to which they are sensitive to perceived deficits in their social connections, but evidence suggests that they nevertheless construe the nature of their social connections similarly. This construal can be thought of as a mental representation of a multi-faceted social experience. A three-dimensional mental representation has been identified with the UCLA Loneliness Scale and consists of Intimate, Relational, and Collective Connectedness reflecting beliefs about one''s individual, dyadic, and collective (group) social value, respectively. Moreover, this mental representation has been replicated with other scales and validated across age, gender, and racial/ethnic lines in U.S. samples. The purpose of this study is to evaluate the extent to which this three-dimensional representation applies to people whose social lives are experienced in a collectivistic rather than individualistic culture. To that end, we used confirmatory factor analyses to assess the fit of the three-dimensional mental structure to data collected from Chinese people living in China. Two hundred sixty-seven young adults (16–25 yrs) and 250 older adults (50–65 yrs) in Beijing completed the revised UCLA Loneliness Scale and demographic and social activity questionnaires. Results revealed adequate fit of the structure to data from young and older Chinese adults. Moreover, the structure exhibited equivalent fit in young and older Chinese adults despite changes in the Chinese culture that exposed these two generations to different cultural experiences. Social activity variables that discriminated among the three dimensions in the Chinese samples corresponded well with variables that discriminated among the three dimensions in the U.S.-based samples, indicating cultural commonalities in the factors predicting dimensions of people''s representations of their social connections. Equivalence of the three-dimensional structure is relevant for an understanding of cultural differences in the sources of loneliness and social connectedness.     

Visualization and curve-parameter estimation strategies for efficient exploration of phenotype microarray kinetics

Background

The Phenotype MicroArray (OmniLog® PM) system is able to simultaneously capture a large number of phenotypes by recording an organism''s respiration over time on distinct substrates. This technique targets the object of natural selection itself, the phenotype, whereas previously addressed ‘-omics’ techniques merely study components that finally contribute to it. The recording of respiration over time, however, adds a longitudinal dimension to the data. To optimally exploit this information, it must be extracted from the shapes of the recorded curves and displayed in analogy to conventional growth curves.

Methodology

The free software environment R was explored for both visualizing and fitting of PM respiration curves. Approaches using either a model fit (and commonly applied growth models) or a smoothing spline were evaluated. Their reliability in inferring curve parameters and confidence intervals was compared to the native OmniLog® PM analysis software. We consider the post-processing of the estimated parameters, the optimal classification of curve shapes and the detection of significant differences between them, as well as practically relevant questions such as detecting the impact of cultivation times and the minimum required number of experimental repeats.

Conclusions

We provide a comprehensive framework for data visualization and parameter estimation according to user choices. A flexible graphical representation strategy for displaying the results is proposed, including 95% confidence intervals for the estimated parameters. The spline approach is less prone to irregular curve shapes than fitting any of the considered models or using the native PM software for calculating both point estimates and confidence intervals. These can serve as a starting point for the automated post-processing of PM data, providing much more information than the strict dichotomization into positive and negative reactions. Our results form the basis for a freely available R package for the analysis of PM data.     

Crowding by invisible flankers

Background

Human object recognition degrades sharply as the target object moves from central vision into peripheral vision. In particular, one''s ability to recognize a peripheral target is severely impaired by the presence of flanking objects, a phenomenon known as visual crowding. Recent studies on how visual awareness of flanker existence influences crowding had shown mixed results. More importantly, it is not known whether conscious awareness of the existence of both the target and flankers are necessary for crowding to occur.

Methodology/Principal Findings

Here we show that crowding persists even when people are completely unaware of the flankers, which are rendered invisible through the continuous flash suppression technique. Contrast threshold for identifying the orientation of a grating pattern was elevated in the flanked condition, even when the subjects reported that they were unaware of the perceptually suppressed flankers. Moreover, we find that orientation-specific adaptation is attenuated by flankers even when both the target and flankers are invisible.

Conclusions

These findings complement the suggested correlation between crowding and visual awareness. What''s more, our results demonstrate that conscious awareness and attention are not prerequisite for crowding.     

Memory for events and their spatial context: models and experiments

The computational role of the hippocampus in memory has been characterized as: (i) an index to disparate neocortical storage sites; (ii) a time-limited store supporting neocortical long-term memory; and (iii) a content-addressable associative memory. These ideas are reviewed and related to several general aspects of episodic memory, including the differences between episodic, recognition and semantic memory, and whether hippocampal lesions differentially affect recent or remote memories. Some outstanding questions remain, such as: what characterizes episodic retrieval as opposed to other forms of read-out from memory; what triggers the storage of an event memory; and what are the neural mechanisms involved? To address these questions a neural-level model of the medial temporal and parietal roles in retrieval of the spatial context of an event is presented. This model combines the idea that retrieval of the rich context of real-life events is a central characteristic of episodic memory, and the idea that medial temporal allocentric representations are used in long-term storage while parietal egocentric representations are used to imagine, manipulate and re-experience the products of retrieval. The model is consistent with the known neural representation of spatial information in the brain, and provides an explanation for the involvement of Papez''s circuit in both the representation of heading direction and in the recollection of episodic information. Two experiments relating to the model are briefly described. A functional neuroimaging study of memory for the spatial context of life-like events in virtual reality provides support for the model''s functional localization. A neuropsychological experiment suggests that the hippocampus does store an allocentric representation of spatial locations.