Sequential learning in non-human primates

Sequential learning plays a role in a variety of common tasks, such as human language processing, animal communication, and the learning of action sequences. In this article, we investigate sequential learning in non-human primates from a comparative perspective, focusing on three areas: the learning of arbitrary, fixed sequences; statistical learning; and the learning of hierarchical structure. Although primates exhibit many similarities to humans in their performance on sequence learning tasks, there are also important differences. Crucially, non-human primates appear to be limited in their ability to learn and represent the hierarchical structure of sequences. We consider the evolutionary implications of these differences and suggest that limitations in sequential learning may help explain why non-human primates lack human-like language.     

Blood pressure hyperreactivity in non-human primates during dietary sodium combined with behavioral stress

The potential for behavioral stress alone or combined with dietary salt to augment pressor reactivity to the onset of daily experimental sessions was examined in normotensive, intact baboons over the course of four months. During twice daily experimental sessions, adult male baboons experienced food/shock conflict such that lever pulling not only served to earn food, but was also occasionally punished with cued mild electric shock. Blood pressure and heart rate were measured during a baseline period of fixed-ratio food reinforcement (3 weeks), during conflict stress (2 weeks), and after dietary salt was added to the daily conflict protocol (CONFLICT + SODIUM, 3 weeks). Reactivity, i.e., acute changes in blood pressure and heart rate to the daily experimental sessions, was not evident during food reinforcement sessions nor during the CONFLICT stress alone condition. The addition of a high salt diet virtually doubled blood pressure increases and heart rate decreases to the onset of experimental sessions. Average reactivities during CONFLICT + SODIUM periods were 11.2/7.9% delta for SBP/DBP (systolic/diastolic blood pressure, mmHg), and -5.65% delta for HR (heart rate, BPM). Neither atenolol nor hydrochlorothiazide diuretic significantly altered cardiovascular reactivity during CONFLICT + SODIUM in comparison to a preceding non-drug CONFLICT + SODIUM period. When atenolol and diuretic effects were directly compared, atenolol mildly augmented, while diuretic mildly decreased DBP but not SBP reactivity during CONFLICT + SODIUM. Reactivity was eliminated after salt loading and behavioral sessions were terminated. These findings provide evidence that enhanced salt ingestion may synergistically act with behavioral stress to produce pressor hyperresponsiveness to otherwise benign environmental events.     

The effects of intradimensional and extradimensional shifts on visual discrimination learning in humans and non-human primates

Human subjects and non-human primates (the common marmoset) were trained on a series of reversals of both a simple (stimuli varying along one dimension) and compound (stimuli varying along two different dimensions) visual discrimination, using computer-generated stimuli. They were then shifted to a third series of reversals using completely novel compound stimuli. Those humans and marmosets for which the previously relevant dimension remained relevant, following the shift (shapes to shapes or lines to lines; intradimensional shift) made fewer errors than those for which the previously irrelevant dimension became relevant (shapes to lines or lines to shapes; extradimensional shift). These findings suggest that both humans and marmosets can learn to attend to the specific attributes or dimensions of a stimulus and use this information in visual discrimination learning.     

Prenatal depression effects on early development: A review

This review of recent research on prenatal depression suggests that it is a strong predictor of postpartum depression and is more common than postpartum depression. Prenatal depression has been associated with excessive activity and growth delays in the fetus as well as prematurity, low birthweight, disorganized sleep and less responsiveness to stimulation in the neonate. Infants of depressed mothers have difficult temperament, and later in development attentional, emotional and behavioral problems have been noted during childhood and adolescence, as well as chronic illnesses in adulthood. Several variables have confounded the effects of prenatal depression including comorbid anxiety and anger as well as stressful life events. Potential mediating variables are low prenatal maternal dopamine and serotonin levels and elevated cortisol and norepinephrine. The associated intrauterine artery resistance may limit blood flow, oxygen and nutrients to the fetus. Some studies also suggest the heritability of developmental problems for the children of prenatally depressed mothers, including ADHD and antisocial behavior. Multivariate, longitudinal research is needed to disentangle these confounding and mediating variables.     

Neurophysiology and neuroanatomy of reflexive and voluntary saccades in non-human primates

A multitude of cognitive functions can easily be tested by a number of relatively simple saccadic eye movement tasks. This approach has been employed extensively with patient populations to investigate the functional deficits associated with psychiatric disorders. Neurophysiological studies in non-human primates performing the same tasks have begun to provide us with insights into the neural mechanisms underlying many cognitive functions. Here, we review studies that have investigated single neuron activity in the superior colliculus (see glossary), frontal eye field, supplementary eye field, dorsolateral prefrontal cortex, anterior cingulate (see glossary) cortex and lateral intraparietal area associated with the performance of visually guided saccades, anti-saccades and memory-guided saccades in awake behaving monkeys.     

Neurophysiology and neuroanatomy of reflexive and voluntary saccades in non-human primates

A multitude of cognitive functions can easily be tested by a number of relatively simple saccadic eye movement tasks. This approach has been employed extensively with patient populations to investigate the functional deficits associated with psychiatric disorders. Neurophysiological studies in non-human primates performing the same tasks have begun to provide us with insights into the neural mechanisms underlying many cognitive functions. Here, we review studies that have investigated single neuron activity in the superior colliculus (see glossary), frontal eye field, supplementary eye field, dorsolateral prefrontal cortex, anterior cingulate (see glossary) cortex and lateral intraparietal area associated with the performance of visually guided saccades, anti-saccades and memory-guided saccades in awake behaving monkeys.     

Implementation of a brief early intervention in times of socio-economic crisis: effects on parental stress

The paper investigates the effect of brief early intervention on parental stress in the midst of a socio-economic crisis, such as the one that struck Greece in the past decade. During this period, a psychoanalytically oriented prevention programme with parents and their infants/young children, named ‘Early Intervention Programme’, was designed and implemented in the Department of Child Psychiatry at ‘Aghia Sophia’ Children’s Hospital in Athens, Greece. The families that attended the programme were asked to participate in a research study regarding its effectiveness; data were collected from 102 mothers and 73 fathers. This paper presents the statistical findings regarding parental stress, mainly because it is a factor that has systematically been shown to negatively influence several aspects of a child’s development, but also because our hypothesis was that parental stress would be influenced by the negative external conditions. The results showed that both mothers’ and fathers’ stress levels were high before their participation to the programme (with fathers’ Total Stress scores falling within the clinical range), while they decreased to a statistically significant level after the completion of the programme. These findings are discussed in conjunction with some illustrative clinical material. Based on these, it is argued that the implementation of a psychoanalytically oriented brief early intervention programme with parents and infants/young children can alleviate parental stress, and thus support the parental capacity to efficiently deal with the high demands of early development, even in periods of economic crisis where the tensions for young parents are significant and the available mental health resources are scarce.     

Brain structures playing a crucial role in the representation of tools in humans and non-human primates

The cortical representation of concepts varies according to the information critical for their development. Living categories, being mainly based upon visual information, are bilaterally represented in the rostral parts of the ventral stream of visual processing; whereas tools, being mainly based upon action data, are unilaterally represented in a left-sided fronto-parietal network. The unilateral representation of tools results from involvement in actions of the right side of the body.     

Cerebrospinal fluid concentrations of biogenic amines and corticotropin-releasing factor in adolescent non-human primates as a function of the timing of adverse early rearing

Adolescent bonnet macaques nursed as infants by mothers facing unpredictable requirements for food procurement (variable foraging demand, VFD) display persistent neurobiological disturbances. This study examined the long-term neurochemical and behavioral effects of adverse rearing initiated later in infancy than in previous cohorts of subjects to test the hypothesis that the timing of an early adverse experience would influence patterns of biobehavioral outcome. Cisternal cerebrospinal fluid (CSF) monoamine and corticotropin-releasing factor (CRF) concentrations were obtained from 20 bonnet macaques (11 VFD-reared and 9 normally reared controls) approximately 2 years after the end of differential rearing. VFD-reared primates displayed on multiple samplings significantly lower CSF CRF concentrations and higher CSF 5-hydroxyindoleacetic acid (5-HIAA) concentration compared to controls. In the VFD-reared, significant inverse correlations between CRF and all three monoamines were found (5-HIAA, 3-methoxy-4-hydroxyphenethyleneglycol and homovanillic acid), most prominently for 5-HIAA. In controls, but not VFD-reared subjects, CSF CRF was positively correlated with changes in "gregariousness" upon presentation of a fear stimulus. VFD-reared subjects displayed greater baseline hierarchical engagement than controls. In contrast to prior findings, in which rearing under VFD conditions at an earlier age led to increased CSF CRF compared with controls, CSF CRF was lower after later exposure to VFD rearing than in controls. Thus, the timing of exposure to VFD conditions early in life evidently determines whether CSF CRF was found to be elevated or decreased, within the context of increased serotonin metabolism, during the course of primate maturation.     

Aging and cardiovascular reactivity to stress: longitudinal evidence for changes in stress reactivity

Although age differences in cardiovascular function are well documented, little research has provided longitudinal evidence for age-related changes in cardiovascular reactivity to stress. In this study, the authors report such data from a follow-up of their prior work (B. N. Uchino, D. Uno, J. Holt-Lunstad, & J. B. Flinders, 1999) with participants between the ages of 30 to 70 (n=108, mean follow-up=10 months, range=7 to 16 months). Results revealed longitudinal evidence for an age-related increase in systolic blood-pressure reactivity and parasympathetic withdrawal to acute stress. The implications of these findings are discussed in light of the increased cardiovascular disease risk with age, as well as the links between aging, emotions, and physiology.     

A meta-analysis and systematic review of reactivity to judgements of learning

Judgements of learning (JoL) are often used in memory research as a means for assessing an individual’s metacognitive beliefs about their learning. JoL have been shown to reliably predict performance as well as learning behaviours and decisions . Participants may, however, modify their behaviour in response to performing JoL. There has, however, been little consensus as to the reliability and direction of the effect. We report on a meta-analyses that assesses the evidence that memory performance is reactive to JoL. The results indicate that overall providing JoL does not have a significant effect on memory performance (g?=?0.054, 95% CI ?0.027 to 0.135). However, sub-groups analysis showed that this effect depends on the nature of the stimuli to be recalled, with moderate positive reactivity observed for related word pairs (g?=?0.323, 95% CI 0.083 to 0.563) and word lists (g?=?0.384, 95% CI 0.146 to 0.622) but no reactivity when pairs were unrelated or a mixture of related and unrelated pairs. These results indicate that researchers should be aware that eliciting JoL may well influence participants’ underlying encoding processes, especially when using related word pairs or word lists.     

Segmentation of the speech stream in a non-human primate: statistical learning in cotton-top tamarins

Previous work has shown that human adults, children, and infants can rapidly compute sequential statistics from a stream of speech and then use these statistics to determine which syllable sequences form potential words. In the present paper we ask whether this ability reflects a mechanism unique to humans, or might be used by other species as well, to acquire serially organized patterns. In a series of four experimental conditions, we exposed a New World monkey, the cotton-top tamarin (Saguinus oedipus), to the same speech streams used by Saffran, Aslin, and Newport (Science 274 (1996) 1926) with human infants, and then tested their learning using similar methods to those used with infants. Like humans, tamarins showed clear evidence of discriminating between sequences of syllables that differed only in the frequency or probability with which they occurred in the input streams. These results suggest that both humans and non-human primates possess mechanisms capable of computing these particular aspects of serial order. Future work must now show where humans' (adults and infants) and non-human primates' abilities in these tasks diverge.     

Family interaction and suicidal behaviour: a brief review

This paper reviews those research studies which have investigated suicidal behaviour in the context of the family. It is proposed that in families a subculture of distress management develops not from random deviations but from familial and cultural expectations of how distress can be managed. A number of factors are presented indicating suicide potential:

• a pattern of marked hostility,

• a pattern of role disturbance and role failure,

• a process of escalation when developmental crises occur in the management of family life-cycle transitions,

• a symbiotic attachment between partners which tolerates no autonomy,

• an intolerance of crisis,

• a relationship between the management of crises, family conflict and family organization,

• suicidal behaviour as a pattern of communication.

A family tradition of crisis management by symptoms and the presence of intra-familial conflict are seen as critical variables.     

Imaginary audience and personal fable: a brief review

A review of the literature was conducted on two aspects of adolescent egocentrism: the imaginary audience and the personal fable. Results yielded contradictory findings in most areas of the research. Reasons for these contradictions are explored and suggestions for future research presented.     

Exploration in outbred mice covaries with general learning abilities irrespective of stress reactivity, emotionality, and physical attributes

Across multiple learning tasks (that place different sensory, motor, and information processing demands on the animals), we have found that the performance of mice is commonly regulated by a single factor ("general learning") that accounts for 30-40% of the variance across individuals and tasks. Furthermore, individuals' general learning abilities were highly correlated with their propensity to engage in exploration in an open field, a behavior that is potentially stress-inducing. This relationship between exploration in the open field and general learning abilities suggests the possibility that variations in stress sensitivity/responsivity or related emotional responses might directly influence individuals' general learning abilities. Here, the relationship of sensory/motor skills and stress sensitivity/emotionality to animals' general learning abilities were assessed. Outbred (CD-1) mice were tested in a battery of six learning tasks as well as 21 tests of exploratory behavior, sensory/motor function and fitness, emotionality, and stress reactivity. The performances of individual mice were correlated across six learning tasks, and the performance measures of all learning tasks loaded heavily on a single factor (principal component analysis), accounting for 32% of the variability between animals and tasks. Open field exploration and seven additional exploratory behaviors (including those exhibited in an elevated plus maze) also loaded heavily on this same factor, although general activity, sensory/motor responses, physical characteristics, and direct measures of fear did not. In a separate experiment, serum corticosterone levels of mice were elevated in response to a mild environmental stressor (confinement on an elevated platform). Stress-induced corticosterone levels were correlated with behavioral fear responses, but were unsystematically related to individuals' propensity for exploration. In total, these results suggest that although general learning abilities are strongly related to individuals' propensity for exploration, this relationship is not attributable to variations in sensory/motor function or the individuals' physiological or behavioral sensitivity to conditions that promote stress or fear.     

Androgens and aggressive behavior in primates: A review

This review deals with possible central and peripheral effects of androgens upon primate aggressive behavior. One problem that clouds interpretation of experimental work is that measurements of dominance have often been employed, such as competition tests for food and water. Such measures often do not correlate with those obtained by quantifying aggressive interactions. It should be remembered that very few of the 188 primate species have been studied experimentally and that great behavioral and physiological diversity occurs within the order. Therefore, generalizations about the effects of androgens upon aggressive behavior in primates (including man) should be made with caution. Testosterone has an organizing influence upon the foetal brain of rhesus monkeys and may affect the development of neural mechanisms which govern aggression in males. More data are required on primates, however, since rhesus monkeys show some important differences from rodents as regards the effects of androgen upon sexual differentiation of the hypothalamus. In future, marmosets may provide a suitable model for such studies, because there is evidence that sexual differentiation of brain by androgen occurs postnatally in these monkeys. At puberty, male primates show a variety of behavioral changes and, during adulthood, males of seasonally breeding species may be more aggressive during the mating season, when testosterone levels are maximal. This does not indicate a causative relationship between testosterone and aggressive responses, because castration and androgen treatments have little effect upon aggression in prepubertal or adult males of several primate species. Androgens have pronounced effects on sexual responses in adult male monkeys, but their central effects upon aggression are much less important than among rodents. Elec trical stimulation of hypothalamic pathways has been employed to evoke aggressive behavior in marmosets and rhesus monkeys. In the rhesus, preliminary evidence indicates that such pathways show some sensitivity to androgens. In rodents it is known that these areas are richly supplied with monoaminergic neurons, which play an important role in aggressive behavior. There is little evidence on primates, however, and this remains a crucial topic for future research. Peripheral effects of androgens should also be considered. Many prosimians and New World monkeys use scent-marking behaviors and, in males, androgen-dependent chemical cues may be involved in sexual recognition and territorial behavior. This possibility awaits investigation. Finally, plasma testosterone levels may alter as a function of aggression itself; thus levels decrease if male rhesus monkeys are defeated by conspecifics. This might occur because neural events associated with giving (or receiving) aggression also influence pituitary function and hence alter gonadal testosterone secretion. Theoretically, it is possible that such changes in circulating testosterone might affect aggressive behavior via a feedback action on the brain, but the experimental evidence does not support such a view.     

History,philosophy, and science teaching: A brief review

School science education is currently the subject of much debate. Historians and philosophers of science should play a role in this debate. Since the late nineteenth century there has been a persistent, if minor, tradition arguing for the incorporation of historical and philosophical dimensions in the teaching of school science. With the current crisis in science teaching, there are encouraging signs that more attention is being paid to this tradition. What is required is much greater collaboration between philosophers, historians, and science educators, particularly in the training of teachers.This article is a shortened version of my 1988, A Role for History and Philosophy in Science Teaching, inEducational Philosophy and Theory 20 (2). All references are to the following History, Philosophy, and Science Teaching: A Bibliography.This special number ofSynthese is part of a large international project on the place of history and philosophy in science teaching. Special issues ofEducational Philosophy and Theory, Interchange, andStudies in Philosophy and Education are being produced. An international conference on the subject will be held at Florida State University in November 1989. Details of the journals and the conference can be obtained from the author.The project commenced while the author was on leave at Florida State University in 1987. It began with a gracious invitation from Jaakko Hintikka to guest edit this number, and was furthered with the support and encouragement of David Gruender. I thank them both, and also the Philosophy Department for its hospitality. Special appreciation is due to the nearly 30 authors who have contributed papers to the project. I hope that their efforts will re-open the needed dialogue between historians, philosophers, and science educators.     

When bad stress goes good: increased threat reactivity predicts improved category learning performance

The way in which we respond to everyday stressors can have a profound impact on cognitive functioning. Maladaptive stress responses in particular are generally associated with impaired cognitive performance. We argue, however, that the cognitive system mediating task performance is also a critical determinant of the stress-cognition relationship. Consistent with this prediction, we observed that stress reactivity consistent with a maladaptive, threat response differentially predicted performance on two categorization tasks. Increased threat reactivity predicted enhanced performance on an information-integration task (i.e., learning is thought to depend upon a procedural-based memory system), and a (nonsignificant) trend for impaired performance on a rule-based task (i.e., learning is thought to depend upon a hypothesis-testing system). These data suggest that it is critical to consider both variability in the stress response and variability in the cognitive system mediating task performance in order to fully understand the stress-cognition relationship.