Uncovering the richness of the stimulus: structure dependence and indirect statistical evidence

The poverty of stimulus argument is one of the most controversial arguments in the study of language acquisition. Here we follow previous approaches challenging the assumption of impoverished primary linguistic data, focusing on the specific problem of auxiliary (AUX) fronting in complex polar interrogatives. We develop a series of corpus analyses of child-directed speech showing that there is indirect statistical information useful for correct auxiliary fronting in polar interrogatives and that such information is sufficient for distinguishing between grammatical and ungrammatical generalizations, even in the absence of direct evidence. We further show that there are simple learning devices, such as neural networks, capable of exploiting such statistical cues, producing a bias toward correct AUX questions when compared to their ungrammatical counterparts. The results suggest that the basic assumptions of the poverty of stimulus argument may need to be reappraised.     

Imitation: is cognitive neuroscience solving the correspondence problem?

Imitation poses a unique problem: how does the imitator know what pattern of motor activation will make their action look like that of the model? Specialist theories suggest that this correspondence problem has a unique solution; there are functional and neurological mechanisms dedicated to controlling imitation. Generalist theories propose that the problem is solved by general mechanisms of associative learning and action control. Recent research in cognitive neuroscience, stimulated by the discovery of mirror neurons, supports generalist solutions. Imitation is based on the automatic activation of motor representations by movement observation. These externally triggered motor representations are then used to reproduce the observed behaviour. This imitative capacity depends on learned perceptual-motor links. Finally, mechanisms distinguishing self from other are implicated in the inhibition of imitative behaviour.     

‘Goals’ are not an integral component of imitation

Several theories suggest that actions are coded for imitation in terms of mentalistic goals, or inferences about the actor’s intentions, and that these goals solve the correspondence problem by allowing sensory input to be translated into matching motor output. We tested this intention reading hypothesis against general process accounts of imitation using the pen-and-cups task. The task has three components: participants place a pen in one of two cups, using their right or left hand, and one of two grips. Previous research has revealed a colour minimum error pattern; when one of the components is differentially coloured (e.g., one cup is red and the other blue), accuracy is greatest on the coloured dimension. We found the colour minimum error pattern, not only in the standard version of the task, where participants imitate the actions of a human model, but also in three novel variants of the task, in which participants responded on the basis of spatial or arbitrary stimulus–response mappings to ‘geometric’, non-biological stimuli. These stimuli do not afford the attribution of intentions, and therefore our results support generalist theories of imitation by showing that the colour minimum error pattern is due, not to intention reading, but to the operation of task-general processes of perception, attention and motor control.     

Perspectives on observational learning in animals

Observational learning is presumed to have occurred when an organism copies an improbable action or action outcome that it has observed and the matching behavior cannot be explained by an alternative mechanism. Psychologists have been particularly interested in the form of observational learning known as imitation and in how to distinguish imitation from other processes. To successfully make this distinction, one must disentangle the degree to which behavioral similarity results from (a) predisposed behavior, (b) increased motivation resulting from the presence of another animal, (c) attention drawn to a place or object, (d) learning about the way the environment works, as distinguished from what we think of as (e) imitation (the copying of the demonstrated behavior). Several of the processes that may be involved in observational learning are reviewed, including social facilitation, stimulus enhancement, several kinds of emulation, and various forms of imitation.     

Learning the unlearnable: the role of missing evidence

Syntactic knowledge is widely held to be partially innate, rather than learned. In a classic example, it is sometimes argued that children know the proper use of anaphoric one, although that knowledge could not have been learned from experience. Lidz et al. [Lidz, J., Waxman, S., & Freedman, J. (2003). What infants know about syntax but couldn't have learned: Experimental evidence for syntactic structure at 18 months. Cognition, 89, B65-B73.] pursue this argument, and present corpus and experimental evidence that appears to support it; they conclude that specific aspects of this knowledge must be innate. We demonstrate, contra Lidz et al., that this knowledge may in fact be acquired from the input, through a simple Bayesian learning procedure. The learning procedure succeeds because it is sensitive to the absence of particular input patterns--an aspect of learning that is apparently overlooked by Lidz et al. More generally, we suggest that a prominent form of the "argument from poverty of the stimulus" suffers from the same oversight, and is as a result logically unsound.     

The influence of electronic sound effects on learning from televised and live models

Infants rapidly accrue information via imitation from multiple sources, including television and electronic toys. In two experiments, we examined whether adding sound effects to video or live demonstrations would influence imitation by 6-, 12-, and 18-month-olds. In Experiment 1, we added matching and mismatching sound effects to target actions presented by a televised model. We found that 6-month-olds reproduced the target actions regardless of whether the sound effects were matched or mismatched, whereas 12- and 18-month-olds reproduced the actions only when the sound effects were matched. In Experiment 2, we added matching sound effects to target actions presented by a live model. The addition of sound effects disrupted imitation performance by 6-, 12-, and 18-month-olds. Overall, imitation provides a clear behavioral measure of rapid changes in learning from television and electronic toys during infancy. These findings have practical implications for producers and parents regarding learning in the digital age and theoretical implications regarding the development of integrated action-perception representational systems.     

Correspondence effects with manual gestures and postures: a study of imitation

In this study, the authors applied methods and theories from research of stimulus-response compatibility (SRC) to action imitation. In 6 experiments, they adopted the logic of the Simon paradigm (B. Hommel & W. Prinz, 1996) to explore interference between task-relevant symbolic stimulus features (color) and task-irrelevant iconic stimulus features (2 hand gestures and 2 postures). The same 2 hand gestures served as responses. Pronounced correspondence effects for both gestures and postures showed up throughout. In line with theories of SRC, the authors account for these correspondence effects in terms of overlap arising between stimulus and response features in a common representational domain. As a specific extension of this approach, they propose 2 functionally independent mechanisms: One operates movement-based when dynamic information is provided, and the other operates state-based with static postures as stimuli. Implications for theories of both SRC and action imitation are discussed.     

A quantitative evaluation of the AVITEWRITE model of handwriting learning

Much sensory-motor behavior develops through imitation, as during the learning of handwriting by children. Such complex sequential acts are broken down into distinct motor control synergies, or muscle groups, whose activities overlap in time to generate continuous, curved movements that obey an inverse relation between curvature and speed. The adaptive vector integration to endpoint handwriting (AVITEWRITE) model of Grossberg and Paine (2000) [A neural model of corticocerebellar interactions during attentive imitation and predictive learning of sequential handwriting movements. Neural Networks, 13, 999-1046] addressed how such complex movements may be learned through attentive imitation. The model suggested how parietal and motor cortical mechanisms, such as difference vector encoding, interact with adaptively-timed, predictive cerebellar learning during movement imitation and predictive performance. Key psychophysical and neural data about learning to make curved movements were simulated, including a decrease in writing time as learning progresses; generation of unimodal, bell-shaped velocity profiles for each movement synergy; size scaling with isochrony, and speed scaling with preservation of the letter shape and the shapes of the velocity profiles; an inverse relation between curvature and tangential velocity; and a two-thirds power law relation between angular velocity and curvature. However, the model learned from letter trajectories of only one subject, and only qualitative kinematic comparisons were made with previously published human data. The present work describes a quantitative test of AVITEWRITE through direct comparison of a corpus of human handwriting data with the model's performance when it learns by tracing the human trajectories. The results show that model performance was variable across the subjects, with an average correlation between the model and human data of 0.89+/-0.10. The present data from simulations using the AVITEWRITE model highlight some of its strengths while focusing attention on areas, such as novel shape learning in children, where all models of handwriting and the learning of other complex sensory-motor skills would benefit from further research.     

DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES?

Two experiments were conducted to investigate generalized imitation of manual gestures in 1- to 2-year-old infants. In Experiment 1, 6 infants were first trained four baseline matching relations (e.g., when instructed "Do this", to raise their arms after they saw the experimenter do so). Next, four novel gestures that the infants did not match in probe trials were selected as target behaviors during generalized imitation Test 1; models of these gestures were presented on unreinforced matching trials interspersed with intermittently reinforced baseline matching trials. None of the infants matched the target behaviors. To ensure that these behaviors were in the infants' motor skills repertoires, the infants were next trained to produce them, at least once, under stimulus control that did not include an antecedent model of the target behavior. In repeat generalized imitation trials (Test 2), the infants again failed to match the target behaviors. Five infants (3 from Experiment 1) participated in Experiment 2, which was identical to Experiment 1 except that, following generalized imitation Test 1, the motor-skills training was implemented to a higher criterion (21 responses per target behavior), and in a multiple-baseline, across-target-behaviors procedure. In the final generalized imitation test, 1 infant matched one, and another infant matched two target behaviors; the remaining 17 target behaviors still were not matched. The results did not provide convincing evidence of generalized imitation, even though baseline matching was well maintained and the target behaviors were in the infants' motor skills repertoires, raising the question of what are the conditions that reliably give rise to generalized imitation.     

DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES? II. THE EFFECTS OF SKILLS TRAINING AND MULTIPLE EXEMPLAR MATCHING TRAINING

The determinants of generalized imitation of manual gestures were investigated in 1‐ to 2‐year‐old infants. Eleven infants were first trained eight baseline matching relations; then, four novel gestures that the infants did not match in probe trials were selected as target behaviors. Next, in a generalized imitation test in which matching responses to baseline models were intermittently reinforced, but matching responses to target models were not eligible for reinforcement, the infants matched baseline models but not the majority of their target behaviors. To ensure their failure to match the target behaviors was not due to motor constraints, the infants were trained, in a multiple‐baseline procedure, to produce the target responses under stimulus control that did not include an antecedent model of the target behavior. There was no evidence of generalized imitation in subsequent tests. When the infants were next trained to match each target behavior to criterion (tested in extinction) in a multiple‐baseline‐across‐behaviors procedure, only 2 infants continued to match all their targets in subsequent tests; the remaining infants matched only some of them. Seven infants were next given mixed matching training with the target behaviors to criterion (tested in extinction); they subsequently matched these targets without reinforcement when interspersed with trials on which matching responses to baseline models were intermittently reinforced. In repeat tests, administered at 3‐week intervals, these 7 children (and 2 that did not take part in mixed matching training) continued to match most of their target behaviors. The results support a trained matching account, but provide no evidence of generalized imitation, in 1‐ to 2‐year‐old infants.     

Planarity and segmentation in stereoscopic matching

The matching of stereograms which contain periodic patterns suggests ways in which the stereo correspondence problem may be solved in human vision. The stereograms seem to be segmented by coarse-scale features. Within each segment a set of matches approximating a plane is chosen. In regions with periodic patterns there may be many such planar sets, and the disparity of coarse-scale features seems to guide the choice of a particular set. This emphasis on planarity may reflect the occurrence of correlation-like operations in cortical neurons. An attractive possibility is that segmentation effectively delimits areas of the visual field within which disparities are likely to be slow changing (eg local tangent planes to surfaces) so that the correlation sums evaluated in a segment can give the best estimate of depth. A mechanism of this kind cannot account for all of stereo matching, since not all visual objects are well described by ensembles of planes. But it is likely to be a component of the matching system which is particularly important where images are 'noisy' and averaging is needed to extract reliable disparities.     

Primate Culture and Social Learning

The human primate is a deeply cultural species, our cognition being shaped by culture, and cultural transmission amounting to an “epidemic of mental representations” (Sperber, 1996). The architecture of this aspect of human cognition has been shaped by our evolutionary past in ways that we can now begin to discern through comparative studies of other primates. Processes of social learning (learning from others) are important for cognitive science to understand because they are cognitively complex and take many interrelated forms; they shape traditions, cultures and nonsocial aspects of cognition; and in turn they may be shaped by their cultural context. The study of primate social learning and culture has in recent years enjoyed a renaissance, providing a wealth of new findings, key aspects of which are reviewed. The focus is on cognitive issues, including learning about the consequences, sequential structure and hierarchical organization of actions; relating stored knowledge to the assimilation of new social knowledge; feedback guiding the construction of imitations; conceptual grasp of imitation; and the reciprocal relationship between social learning and culture.     

A new method to evaluate order and accuracy of inaccurately and incompletely reproduced movement sequences

Studying imitation learning of long sequences requires the evaluation of inaccurately and incompletely reproduced movement sequences. In order to evaluate the movement reproduction, it has to be assigned to the original stimulus. We developed an assignment algorithm that considers the Spatial Neighborhood and Order of reproduction (SNOA). To evaluate the features of this analysis it was applied to human performance during learning of long pointing sequences under two conditions: stimulus-guided reproduction with high spatial accuracy and imitation learning with low spatial accuracy. The results were compared with a simple assignment considering Spatial Neighborhood only (SNA) and with a Manual Assignment (MA). In the stimulus-guided reproduction the error measures did not differ between the algorithms. In contrast, with imitation learning, SNOA and MA generated higher estimates of order and omission errors than SNA. The results show that SNOA can be used to automatically quantify the similarity of both movement structure and metric information between long target sequences and inaccurate and incomplete movement reproductions.     

Imitative learning in Japanese quail (Coturnix japonica) using the bidirectional control procedure

In the bidirectional control procedure, observers are exposed to a conspecific demonstrator responding to a manipulandum in one of two directions (e.g., left vs. right). This procedure controls for socially mediated effects (the mere presence of a conspecific) and stimulus enhancement (attention drawn to a manipulandum by its movement), and it has the added advantage of being symmetrical (the two different responses are similar in topography). Imitative learning is demonstrated when the observers make the response in the direction that they observed it being made. Recently, however, it has been suggested that when such evidence is found with a predominantly olfactory animal, such as the rat, it may result artifactually from odor cues left on one side of the manipulandum by the demonstrator. In the present experiment, we found that Japanese quail, for which odor cues are not likely to play a role, also showed significant correspondence between the direction in which the demonstrator and the observer push a screen to gain access to reward. Furthermore, control quail that observed the screen move, when the movement of the screen was not produced by the demonstrator, did not show similar correspondence between the direction of screen movement observed and that performed by the observer. Thus, with the appropriate control, the bidirectional procedure appears to be useful for studying imitation in avian species.     

The mirror neuron system: grasping others’ actions from birth?

In the adult human brain, the presence of a system matching the observation and the execution of actions is well established. This mechanism is thought to rely primarily on the contribution of so-called 'mirror neurons', cells that are active when a specific gesture is executed as well as when it is seen or heard. Despite the wealth of evidence detailing the existence of a mirror neuron system (MNS) in the adult brain, little is known about its normal development. Yet, a better understanding of the MNS in infants would be of considerable theoretical and clinical interest, as dysfunctions within the MNS have been demonstrated in neurodevelopmental disorders such as autism spectrum disorder. Arguments in favor of an innate, or very early, mechanism underlying action understanding mainly come from studies of neonatal imitation, the existence of which has been questioned by some. Here, we review evidence suggesting the presence of an MNS in the human child, as well as work that suggests, although indirectly, the existence of a mechanism matching the perception and the execution of actions in the human newborn.     

Effects of irrelevant spatial S-R compatibility depend on stimulus complexity

Summary Choice-reaction time is known to depend on the spatial correspondence of stimulus and response, even if the stimulus location is irrelevant to the task (Simon effect). An experiment investigated whether this effect depends on stimulus complexity — i. e., on whether properties of the stimulus render stimulus discrimination easy or difficult. It was hypothesized that high demands on discrimination slow down the processing of stimulus identity in relation to location, so that the facilitating or conflicting location code has more time to decay, thus losing impact on response selection. In fact, the results revealed an effect of irrelevant spatial S-R correspondence with easy, but not with difficult, stimulus discrimination. This finding resolves an apparent contradiction between the results of several previous experiments on the Simon effect.The other central argument rests on findings of Stoffer (1991) obtained with a single frame. These, however, have recently been challenged by Hommel (1993 b).     

Modeling how, when, and what is learned in a simple fault-finding task

We have developed a process model that learns in multiple ways while finding faults in a simple control panel device. The model predicts human participants' learning through its own learning. The model's performance was systematically compared to human learning data, including the time course and specific sequence of learned behaviors. These comparisons show that the model accounts very well for measures such as problem-solving strategy, the relative difficulty of faults, and average fault-finding time. More important, because the model learns and transfers its learning across problems, it also accounts for the faster problem-solving times due to learning when examined across participants, across faults, and across the series of 20 trials on an individual participant basis. The model shows how learning while problem solving can lead to more recognition-based performance, and helps explain how the shape of the learning curve can arise through learning and be modified by differential transfer. Overall, the quality of the correspondence appears to have arisen from procedural, declarative, and episodic learning all taking place within individual problem-solving episodes.     

Identity matching and oddity learning in patients with moderate to severe Alzheimer-type dementia

Discrimination learning was investigated in patients with moderate to severe Alzheimer-type dementia (AD), comparing their performance with age-matched controls. Four AD patients were trained to criterion on identity matching and then shifted to the same task with novel stimuli. The AD patients showed no savings in learning to match novel stimuli, whereas a comparative group of four control subjects rapidly learned the novel matching discrimination, maintaining criterion performance on the transfer test. A second group of four patients was initially trained on oddity, taking a similar number of trials to reach criterion as the matching group. When these patients were subsequently shifted to the matching task with novel stimuli, they performed substantially worse than the first group of patients who had learned the matching task in the first stage. The lack of positive transfer in the shift between matching to matching suggests that the AD patients solved the identity-matching task on the basis of stimulus-response associations rather than a rule. The presence of negative transfer after shifting from oddity to matching may be explained by a pre-disposition to respond to a novel stimulus that is carried over into the matching task, but this warrants further investigation, as indicated in the discussion.     

Cowie on the Poverty of Stimulus

My paper defends the use of the poverty of stimulus argument (POSA) for linguistic nativism against Cowie's (1999) counter-claim that it leaves empiricism untouched. I first present the linguistic POSA as arising from a reflection on the generality of the child's initial state in comparison with the specific complexity of its final state. I then show that Cowie misconstrues the POSA as a direct argument about the character of the pld. In this light, I first argue that the data Cowie marshals about the pld does not begin to suggest that the POSA is unsound. Second, through a discussion of the so-called `auxiliary inversion rule', I show, by way of diagnosis, that Cowie misunderstands both the methodology of current linguistics and the complexity of the data it is obliged to explain.     

Development as Happiness: The Subjective Perception of Happiness and UNDP’s Analysis of Poverty, Wealth and Development

This paper examines to what extent the concept of happiness is complementary to the United Nations Development Program's (UNDP) human development approach in the evaluation of poverty, wealth and development. The deconstruction of UNDP's discourse on and its measurement of these concepts show that its perspective is highly arbitrary. Poverty is exclusively defined as lack and state of ill-being, inferior to wealth regarded as a state of abundance and well-being. Development then becomes a teleological process trying to promote well-being through abundance. Yet, this external perspective of UNDP on well-being is questioned by the subjective perception of the individuals themselves. Happiness studies—which define happiness as the degree to which an individual judges the overall quality of his life-as-a-whole favorably—prove that higher levels of UNDP's development indicators are not necessarily better for subjective well-being. Despite methodological and conceptual problems, happiness studies discover that the individuals' perception of poverty, wealth and development can differ considerably from UNDP's perspective. Increased income, better objective health and higher levels of education do not automatically lead to greater happiness. Furthermore, additional dimensions essential for human happiness are detected by the research, yet not taken into account by UNDP. A country ranking comparison between the two approaches confirms the different visions of well-being. The integration of a happiness indicator in its analysis of poverty, wealth and development is thus indispensable for UNDP in order to correct its analytical and also practical approach to development.