Unfamiliar Stimuli Research Articles

Social approach–avoidance behavior of a high-anxiety strain of rats: effects of benzodiazepine receptor ligands

To better understand anxiety disorders with social impairments as well as to identify new treatments, it is important to develop preclinical procedures involving social components of anxiety. Recently, a novel procedure was reported: the rat Social Approach-Avoidance (SAA) test. In this test, the time spent by a test rat in a large social compartment containing an unfamiliar stimulus rat reflects the anxiety state of the animal. It was shown that pre-stressing the test rat increased the avoidance of the social compartment as characterized by an increase in the time spent in the nonsocial compartment. (1) To use a high-anxiety strain, F-344 rats, instead of pre-stressed animals, (2) to automate the test by using video tracking to measure time spent in both compartments and their subdivisions, and (3) to validate this modified test with known benzodiazepine receptor ligands. F-344 rats were treated with either chlordiazepoxide or diazepam (benzodiazepine receptor agonists), or RO 19-4603 or FG 7142 (benzodiazepine receptor inverse agonists). The agonists produced anxiolytic-like effects, whereas the inverse agonists produced anxiogenic-like effects. These effects were most marked in the two extreme zones in terms of distance to the stimulus rat. F-344 rats display spontaneous avoidance behavior in the modified SAA procedure, and approach-avoidance behavior in these rats is sensitive to benzodiazepine agonists and inverse agonists in a bidirectional manner. The finding that the assessment of time spent into two virtual zones in each of the compartments markedly increased the sensitivity to both anxiolytics and anxiogenics will be discussed using the concept of physical defensive distance.

Brain electrical tomography (BET) analysis of induced gamma band responses during a simple object recognition task

The formation of cortical object representations requires the activation of cell assemblies, correlated by induced oscillatory bursts above 20 Hz (gamma band), which are characterized by trial-by-trial latency fluctuations around a mean of approximately 300 ms after stimulus onset. The present electroencephalogram (EEG) study was intended to uncover to the generators of induced gamma band responses (GBRs) and to analyze phase-synchronization between these sources. A standard object recognition task was used to elicit gamma activity. At the scalp surface (electrode space), we found an augmentation of induced GBRs after the presentation of meaningful (familiar) as opposed to meaningless (unfamiliar) stimuli, which was accompanied by a dense pattern of significant phase-locking values between distant recording sites. Subsequently, intracranial current density distributions compatible with the observed scalp voltage topographies were estimated by means of VARETA (Variable Resolution Electromagnetic Tomography). In source space brain electrical tomographies (BETs) revealed widespread generators of induced GBRs at temporal, parietal, posterior, and frontal areas. Phase-locking analysis was calculated between re-constructed electrode signals based on separate forward solutions of the observed generators, thereby eliminating the possibly confounding influence of activity from areas not under observation. The results support the view that induced GBRs signify synchronous neuronal activity in a broadly distributed network during object recognition. The localization of the generators of event-related potentials (ERPs), evoked gamma activity, and induced alpha activity revealed different sources as compared to the induced GBR and, thus, seem to mirror complementary functions during the present task as compared to induced high-frequency brain dynamics.

Exploring the correlates of impaired non‐word repetition in Down syndrome

Non‐word repetition, in which participants hear and repeat unfamiliar verbal stimuli, is thought to provide a particularly sensitive measure of verbal short‐term memory capacity. However, performance on this task can also be constrained by hearing and speech production skills, and by an individuals' linguistic knowledge. This study examined real word and non‐word repetition in a sample of 18 children and adolescents with Down syndrome, and compared their performance to that of a control group of 18 typically developing children in order to determine the extent of any impairment in repetition performance in Down syndrome, and the correlates of performance in each group. Individuals with Down syndrome were impaired in repetition performance, although both groups showed similar benefits of linguistic knowledge on repetition accuracy. An analysis of the correlates of non‐word repetition revealed a double dissociation between the patterns of associations seen in the two groups. Among typically developing individuals, non‐word repetition was related to an independent measure of verbal short‐term memory but not to vocabulary knowledge. However, among individuals with Down syndrome, performance was related to vocabulary knowledge but not verbal short‐term memory span. This contrast is consistent with the view that impairment to verbal short‐term memory prevents this system from fully supporting non‐word repetition in Down syndrome.

Moral heuristics or moral competence? reflections on sunstein

by focusing on mistaken judgments, sunstein provides a theory of performance errors without a theory of moral competence. additionally, sunstein's objections to thought experiments like the footbridge and trolley problems are unsound. exotic and unfamiliar stimuli are used in theory construction throughout the cognitive sciences, and these problems enable us to uncover the implicit structure of our moral intuitions.

Is everybody always my friend? Perception of approachability in Williams syndrome

Individuals with Williams syndrome (WS) are well known for their friendly behaviour and tendency to approach strangers indiscriminately as if everybody were their friend. This tendency to approach strangers is mirrored in their ratings of unfamiliar face stimuli. Here we examined their perception of unfamiliar expressive faces and found that individuals with WS do not always see faces as being highly approachable. Happy faces were rated as more approachable by individuals with WS than by controls. In contrast, the other less approachable face stimuli were rated lower on approachability by individuals with WS than by controls. Thus, it appears that although individuals with WS will discriminate people in terms of approachability, they have difficulty inhibiting their strong compulsion towards social interaction. The form of this strong pro-social compulsion is discussed both in terms of friendliness and in terms of the heightened salience of social stimuli (social stimulus attraction).

Anatomical limitations in mental transformations of body parts

Two experiments investigated whether possible and impossible body postures influence mental rotation processes differently considering that anatomical limitations constrain the way in which subjects perform mental transformations of body parts. In Experiment 1, mental rotation was performed on two stimuli presented simultaneously. Both possible and impossible body postures elicited mental rotation, although the mental rotation rate was slower for impossible postures. In Experiment 2, only one stimulus was presented at a time and subjects decided whether it represented a correct body-part configuration or not. A typical mental rotation function was only present for correct body-part configurations. The results are discussed in terms of the familiarity of the stimuli. Unfamiliar stimuli (physically impossible) are rotated via local representations of their parts, whilst global representations are used for rotating familiar (anatomically correct) stimuli.

The role of long-term and short-term familiarity in visual and haptic face recognition

Recent studies have suggested that the familiarity of a face leads to more robust recognition, at least within the visual domain. The aim of our study was to investigate whether face familiarity resulted in a representation of faces that was easily shared across the sensory modalities. In Experiment 1, we tested whether haptic recognition of a highly familiar face (one's own face) was as efficient as visual recognition. Our observers were unable to recognise their own face models from tactile memory alone but were able to recognise their faces visually. However, haptic recognition improved when participants were primed by their own live face. In Experiment 2, we found that short-term familiarisation with a set of previously unfamiliar face stimuli improved crossmodal recognition relative to the recognition of unfamiliar faces. Our findings suggest that familiarisation provides a strong representation of faces but that the nature of the information encoded during learning is critical for efficient crossmodal recognition.

Unconscious Detection of Implicit Expectancies

The detection of unexpected events is a fundamental process of learning. Theories of cognitive control and previous imaging results indicate a prominent role of the prefrontal cortex in the evaluation of the congruency between expected and actual outcome. In most cases, this attributed function is based on results where the person is consciously aware of the discrepancy. In this functional magnetic imaging (fMRI) study, we examined violations of predicted outcomes that did not enter conscious awareness. Two groups were trained with nearly identical material and the effects of new stimuli were assessed after learning. For the first group, the material was arranged with a hidden regularity. In this incidental learning situation, volunteers acquired implicit knowledge about structural response regularities as was demonstrated by an increase in reaction time when introducing new stimuli that violated the learned relations. To differentiate the detection process of stimuli that deviate from learned expectations from more unspecific effects generated by novel, unfamiliar stimuli, the second group was trained with rearranged material without a hidden regularity. No behavioral effects were found for the introduction of new stimuli in the group without implicit learning. Comparing the two groups, specific fMRI effects concerning the violation of implicitly learned expectations were found in the ventral prefrontal cortex and in the medialtemporal lobe. In accord with theories of learning, the results show a direct influence of the detection of prediction errors on the neuronal activity in learning related structures even in the absence of conscious knowledge about the predictions or their violations.

Behaviorally timid rats respond differentially to conventional and atypical neuroleptics

An inhibited temperament can be manifested as simple shyness or as social phobia and is perhaps related to the extreme social dysfunction often accompanying schizophrenia. Here, we present a methodology for selecting subjects and testing changes in social attraction in an animal model of behavioral timidity. In Experiment 1, randomly selected female rats were chronically administered either vehicle only, the conventional neuroleptic haloperidol (0.1 mg/kg) or atypical drugs sulpiride (65 mg/kg) or clozapine (18 mg/kg). The animals were tested over 3 weeks for changes in attraction to a social stimulus. Findings revealed a statistically significant decrease in social investigation in the haloperidol treated animals compared to controls but no significant differences among the other groups. Experiment 2 employed pretests to select behaviorally timid (BT) animals. Only female rats having little initial attraction to unfamiliar non-social and social stimuli were chosen to serve as subjects for the experiment using the same drug exposure regiments and behavioral measures used in experiment 1. Results with pre-selected BT animals indicated that clozapine treated animals significantly increased social investigation whereas chronic exposure to either sulpiride or haloperidol groups did not increase social investigation. Indeed, haloperidol appears to have magnified avoidance of social contact. That there were minimal differences between drug groups on a measure of non-social general activity points to the beneficial increases in investigation from clozapine being specific to social inhibition. Conclusions are that timidity may involve aspects of the serotonergic system uniquely influenced by clozapine, and the animal model of the second experiment may prove useful for studies of the biological underpinnings of behavioral timidity.

Searching for sources of variance in speech recognition: Young adults with normal hearing

In the present investigation, sensory-perceptual abilities of one thousand young adults with normal hearing are being evaluated with a range of auditory, visual, and cognitive measures. Four auditory measures were derived from factor-analytic analyses of previous studies with 18–20 speech and non-speech variables [G. R. Kidd et al., J. Acoust. Soc. Am. 108, 2641 (2000)]. Two measures of visual acuity are obtained to determine whether variation in sensory skills tends to exist primarily within or across sensory modalities. A working memory test, grade point average, and Scholastic Aptitude Test scores (Verbal and Quantitative) are also included. Preliminary multivariate analyses support previous studies of individual differences in auditory abilities (e.g., A. M. Surprenant and C. S. Watson, J. Acoust. Soc. Am. 110, 2085–2095 (2001)] which found that spectral and temporal resolving power obtained with pure tones and more complex unfamiliar stimuli have little or no correlation with measures of speech recognition under difficult listening conditions. The current findings show that visual acuity, working memory, and intellectual measures are also very poor predictors of speech recognition ability, supporting the independence of this processing skill. Remarkable performance by some exceptional listeners will be described. [Work supported by the Office of Naval Research, Award No. N000140310644.]

Le développement de la « rotation mentale » : effets de la saillance de l'axe du stimulus et de son alignement avec la direction verticale

Summary : The development of mental rotation : effect of stimulus axis salience and its alignment with the vertical direction The present study was designed to investigate the effects of the geometrical properties of an object on children's abilities to mentally rotate unfamiliar figures. We report two experiments in which children aged 7, 9 and 11 years were submitted to mental rotation tasks of unfamiliar stimuli. Three unfamiliar shapes composed of four arms were used. For each shape, there was a version with a salient axis (S+) and a version with no salient axis (S—). In experiment one, the reference stimulus always pointed to 0° and the angular disparity with the other stimulus was 0°, 60°, 120" and 180°. In experiment two, the procedure was the same as in experiment 1 except that the reference stimulus could point either to 0° or to 60°. Results of experiment one were congruent with those of Courbois (2000) and suggested that the ability to rotate mentally unfamiliar figures with no salient axis improves with age. Results of experiment two suggested that young children had great difficulty performing the mental rotation task when none of the stimuli was aligned with the vertical direction.

Temperament and Early Experience Form Social Behavior

Individual differences in the way persons respond to stimulation can have important consequences for their ability to learn and their choice of vocation. Temperament is the study of such individual differences, being thought of as the behavioral style of an individual. Common to all approaches in the study of temperament are the notions that it can be identified in infancy, is fairly stable across development, and influences adult personality. We have identified a specific temperament type in infancy that involves heightened distress to novel and unfamiliar stimuli. Infants who exhibit this temperament are likely, as they get older, to display behavioral inhibition-wariness and heightened vigilance of the unfamiliar-particularly in social situations. Our work has also described the underlying biology of this temperament and has linked it to neural systems supporting fear responses in animals. Children displaying behavioral inhibition are at-risk for behavioral problems related to anxiety and social withdrawal.

Is a Picture Worth a Thousand Words? The Flexible Nature of Modality Dominance in Young Children

When presented simultaneously with equally discriminable, but unfamiliar, visual and auditory stimuli, 4-year-olds exhibited auditory dominance, processing only auditory information (Sloutsky & Napolitano, 2003). The current study examined factors underlying auditory dominance. In 6 experiments, 4-year-olds (N=181) were presented with auditory and visual compounds in which (a) the complexity and familiarity of stimuli were systematically varied (Experiments 1-5) and (b) participants were explicitly instructed to attend to a particular modality (Experiment 6). Results indicate that auditory dominance is a special case of flexible modality dominance, which may stem from automatic pulls on attention. Theoretical implications of these results for understanding the development of attention and cross-modal processing, as well as linguistic and conceptual development, are discussed.

Female zebra finches require early song exposure to prefer high-quality song as adults

Song learning in songbirds has been studied extensively in males but not in females. Females prefer songs previously heard, but it is not known whether opportunity for learning during the juvenile period affects the ability of females to judge song quality. We show that early exposure to adult song is required in the development of normal adult female zebra finch, Taeniopygia guttata, song preferences. Females were reared in conditions that varied in the exposure to song. As young adults, these females were tested for song preference using a two-choice speaker protocol with unfamiliar song stimuli. Females reared with adult males preferred tutored (normal-quality) song, whereas females reared without adult males were as likely to prefer untutored (abnormal-quality) song as tutored song. All three groups of females preferred conspecific to canary song but showed no preference for songs that were temporally reversed or played forward. Our results suggest that a normally reared female's preference for songs with more notes and spectral complexity is learned during early exposure to adult males that produce such songs.

Visual XOR tasks are easy for monkeys

Monkeys exhibit great difficulty learning and performing visual classification tasks in which class assignment depends on conjunctions of features — in particular, the exclusive-or (XOR) of two distinct features. This suggests that they might not readily or naturally utilize holistic configural information when identifying images, instead relying upon single diagnostic cues. We hypothesized that familiarity and/or expertise could transform a “hard” XOR task into an easy one, comparable in difficulty to a one-dimensional classification task (in which each object may be identified by a single feature). To address this, we first overtrained monkeys on a one-dimensional classification task. New hybrid stimuli were then constructed by dividing each familiar stimulus into two pieces and re-pairing these pieces within each class. When shown these hybrid stimuli without differential reinforcement, monkeys classified them according to their component parts, reliably and with no impairment to reaction time. They were then trained to classify the hybrids into the opposite categories as their component pieces, while maintaining performance on the original stimuli. They were able to learn this expanded XOR task much more easily and quickly than a simpler XOR classification task involving unfamiliar stimuli. We also investigated performance on the hybrid classification task after prolonged passive exposure to the original stimuli. It appears that monkeys solve classification tasks by finding a diagnostic feature for each object. When this strategy is insufficient, they have great difficulty learning the task. However, familiarity seems on some level to engender complete representations of the stimuli, even though only a small part of each stimulus may be behaviorally relevant. This allows for performance on an XOR task comparable to performance on one-dimensional tasks, possibly by dividing the XOR task into two separate one-dimensional tasks.

Oscillatory brain activity dissociates between associative stimulus content in a repetition priming task in the human EEG.

The retrieval and formation of cortical object representations seem to require the activation of neuronal cell assemblies, correlated by synchronized neuronal activity in the gamma band range (>20 Hz). In the present electroencephalogram (EEG) study we have analysed induced gamma band activity during the repetition of familiar (meaningful) and unfamiliar (meaningless) line drawings. Results showed a broad posterior distribution of induced gamma band responses (GBRs) after the initial presentation of a familiar stimulus. Repeated presentations of the same picture resulted in a decrease of GBRs, accompanied by a decrease in the number of electrode pairs exhibiting significant phase-locking values. These effects might be linked to a 'sharpening' mechanism within a cell assembly representing a familiar object. In contrast, the re-presentation of primed unfamiliar stimuli was associated with an augmentation of gamma power and an increase in significantly phase-locked pairs of electrodes. These findings might be a signature of the formation of a new cortical network representing an object. Event related potentials (ERPs) showed a decrease in amplitude independent of the stimuli's associative content, and, thus, seem to play a complementary role in repetition priming as compared to high-frequency brain dynamics.

A short‐term perceptual priming account of spacing effects in explicit cued‐memory tasks for unfamiliar stimuli

Memory for repeated items improves when presentations are spaced during study. This effect is found in explicit memory tasks using different types of material, different experimental paradigms, and in different subject populations. Two experiments are described where the spacing effect was assessed on a yes/no recognition memory task using words and nonwords as targets. The main results showed that changing the font between repeated occurrences of targets at study did not affect the spacing effect for words, even under shallow encoding conditions, but effectively removed the spacing effect with nonwords. In both experiments, the font manipulation was made between subjects, ruling out explanations in terms of differential attention to particular font conditions. These results provide further support for short‐term perceptual priming accounts of the spacing effect: Semantically‐based repetition priming affects memory for words; perceptual priming mechanisms affect memory for nonwords.

Recognition of competitors by male golden hamsters

Golden hamsters, like many animals, form dominant/subordinate relationships after aggressive encounters. We examined whether behavioral responses by males that won or lost fights would differ toward familiar and unfamiliar male stimulus animals. In Experiment 1, male winners or losers of fights explored an arena containing a confined stimulus animal that was either familiar or novel and had either won or lost a fight. Compared to dominant males, losers spent less time in proximity to stimulus males and investigated them less. Losers also displayed higher levels of stretch-attend postures (indicative of risk assessment) than winners, and they showed more escape and locomotion in response to familiar winners than to unfamiliar winners, indicating recognition of the male that they had lost to. In Experiment 2, losers scent marked less to the odors of a familiar winner than to those of an unfamiliar winner. Thus, male hamsters appear to use familiarity with a former opponent's odors to adaptively regulate their responses to variations in social threat.

Responses of Young Red Jungle Fowl (Gallus gallus) and White Leghorn Layers to Familiar and Unfamiliar Social Stimuli

Social preferences of familiar over unfamiliar social stimuli in chicks may be used to measure sociality, a characteristic important for the welfare of poultry in commercial production. We studied social preferences and reaction to strangers in young White Leghorns and red jungle fowl (Gallus gallus) in 3 tests. All chicks were raised and housed in 2 groups of 34 individuals per breed. At 24 to 29 d of age 38 chicks per breed were tested in 2 runway tests. In the first, chicks had a free choice between familiar and unfamiliar breed members, and in the second the choice was between unfamiliar chicks of their own breed and the other breed. On d 41 to 42, spacing and agonistic interactions of 28 pairs of chicks per breed (in half of the pairs, chicks were unfamiliar to each other) were observed in an open field for 10 min (pair test). In the first runway test, clear preference for familiar chicks and avoidance of unfamiliar social stimuli was found only in Leghorns, whereas both breeds showed a preference for their own breed members in the second runway test. Affiliation to the familiar breed, however, was more pronounced in Leghorns. In the pair test, Leghorns were significantly more involved in agonistic interactions than wild-type chicks. Avoidance of unfamiliar and preference for familiar conspecifics might suggest a weaker capacity of Leghorns to cope with novel social and environmental stimuli, which might have implications for the welfare of the birds in production environments when encountering unfamiliar individuals.

Creating Text for Older Audiences

Creating Text for Older Audiences