Some exact conditional tests of independence forR ×C cross-classification tables

Exact conditional tests of independence in cross-classification tables are formulated based on the ² statistic and statistics with stronger operational interpretations, such as some nominal and ordinal measures of association. Guidelines for the table dimensions and sample sizes for which the tests are economically implemented on a computer are given. Some selected sample sizes and marginal distributions are used in a numerical comparison between the significance levels of the approximate and exact conditional tests based on the ² statistic.The authors are grateful for the suggestions of the referees and for computer funding provided by the Northeast Regional Data Center at the University of Florida.     

Social learning by following: an analysis

Learning by “following”, probably a common means by which behaviors are socially transmitted from adults to young in many species, was analyzed. Pigeons first learned to eat from a human hand. When the hand then approached an operant key and pecked it, the pigeons followed and quickly learned to do the same, thereby demonstrating social learning. When the hand only led the birds to the area of the key, without demonstrating the key-peck response, the birds learned as rapidly as with a key-peck demonstration. Birds also learned, but less reliably and more slowly, when they could observe the hand's responses but were constrained and unable to follow. “Following” was also shown to engender very rapid learning of a more complex, two-member response chain.     

Changes in imitative behavior during early infancy

Changes in imitative behavior and attentiveness were observed in 40 infants when they were 2 to 6 months of age. The facial expressions happy, sad, and surprised were modeled in a trials-to-criterion procedure, and the infants' looking time and mouth movements were recorded by an observer who was unaware of the face being modeled. In addition, the observer recorded her guess as to the expression being modeled by the corresponding expression on the infant's face and rated the infant's expressivity. The results suggested that looking time, correspondence between the mouth expression of the infant and the mouth expression modeled, accuracy of the observer's guess, and expressivity ratings decreased from 2 to 3 and 4 to 6 months. Although matching of mouth movements with the modeled mouth movements and accuracy of guesses were greater than chance over the 2 to 6 month-period, the decreases in these measures suggest that imitative behavior declined across early infancy. The decrease in looking time suggests that imitative behavior and attentiveness may be related and highlights the limitation of this paradigm for assessing the development of imitation during early infancy.     

IMPROVING THE GENERALIZED MNEMONIC PERFORMANCE OF A DOWN'S SYNDROME CHILD1

A training program was conducted to improve the generalized mnemonic performance, or memory, of a Down's Syndrome child. Training was directed at digit-span performance with generalization from training determined by responses to untrained mnemonic performance probes. The digit-span items varied in length from three to five digits. Each length constituted an item class, with each class trained within the framework of a multiple-baseline design. Probes consisted of untrained digit-span items, grammatical sentences, nongrammatical sentences, and match-to-sample items. A training procedure, in which 15 items from each class varied continually from trial to trial and from day to day, resulted in the percentage of correct responses to both training and probe items increasing to levels substantially above baseline. The results demonstrate the effectiveness of the training procedure in improving the generalized mnemonic performance of a Down's Syndrome child.     

Exact tests for the rasch model via sequential importance sampling

Rasch proposed an exact conditional inference approach to testing his model but never implemented it because it involves the calculation of a complicated probability. This paper furthers Rasch’s approach by (1) providing an efficient Monte Carlo methodology for accurately approximating the required probability and (2) illustrating the usefulness of Rasch’s approach for several important testing problems through simulation studies. Our Monte Carlo methodology is shown to compare favorably to other Monte Carlo methods proposed for this problem in two respects: it is considerably faster and it provides more reliable estimates of the Monte Carlo standard error.This Research was supported in part by National Science Foundation grant DMS-0203762 and a University of Pennsylvania Research Foundation grant.The authors are grateful to Don Burdick for helpful comments. In addition, the authors wish to thank the editor, the associate editor, and the referees for their helpful suggestions.This revised article was published online in August 2005 with the PDF paginated correctly.     

The history of imitation in learning theory: the language acquisition process

The concept of imitation has undergone different analyses in the hands of different learning theorists throughout the history of psychology. From Thorndike's connectionism to Pavlov's classical conditioning, Hull's monistic theory, Mowrer's two-factor theory, and Skinner's operant theory, there have been several divergent accounts of the conditions that produce imitation and the conditions under which imitation itself may facilitate language acquisition. In tracing the roots of the concept of imitation in the history of learning theory, the authors conclude that generalized imitation, as defined and analyzed by operant learning theorists, is a sufficiently robust formulation of learned imitation to facilitate a behavior-analytic account of first-language acquisition.     

Neonatal imitation, gaze aversion, and mother-infant interaction

A relationship between elicited imitation in neonates and social interaction has been proposed by several investigators. The present work examines if such a relationship can be found when studying neonatal imitation, gaze aversion, and mother-infant interaction. Thirty-two infants were observed at 2 to 3 days, 3 weeks, and 3 months of age. Imitation of tongue protrusion and mouth opening was assessed in all three observations. In addition, a face-to-face interaction between mother and child was included when the child reached 3 months of age. The most striking result was a negative relationship between the infants' brief gaze aversion observed at 3 months of age while interacting with their mothers and the infants' imitative reactions at 2 to 3 days, 3 weeks, and 3 months of age. Behaviorally, these patterns indicate that high-imitating infants tend to display fewer episodes of brief gaze aversion when interacting with their mothers.     

Preschool children's learning proclivities: When the ritual stance trumps the instrumental stance

Previous research has demonstrated an efficiency bias in social learning whereby young children preferentially imitate the functional actions of a successful individual over an unsuccessful group member. Our aim in the current research was to examine whether this bias remains when actions are presented as conventional rather than instrumental. Preschool children watched videos of an individual and a group member. The individual always demonstrated a successful instrumental action and the group member an unsuccessful action that was either causally transparent or opaque. Highlighting the selective nature of social learning, children copied the group at higher rates when the demonstrated actions were causally opaque than when they were causally transparent. This research draws attention to the influence of conventional/ritual‐like actions on young children's learning choices and emphasizes the role of this orientation in the development of human‐specific cumulative culture.     

Fourteen‐Month‐Olds' Imitation of Differently Aged Models

Studies comparing adult and peer imitation are rare and have to date provided mixed results. The aim of the present study was to investigate 14‐month‐olds' imitation of different actions (novel versus familiar) performed by televised models of different age groups (peers, older children or adults). In two experiments, we investigated infants' imitative performance when observing a novel action (Experiment 1) and familiar actions (Experiment 2). The results showed that the likelihood of imitating a novel action increased as the age of the model increased. The opposite was true for familiar actions where infants imitated the peer more frequently than either the older child or the adult model. These findings are discussed in relation to infants' ability to take into account a model's characteristics such as age when imitating actions. Copyright © 2011 John Wiley & Sons, Ltd.     

Does the body talk to the body? The relationship between different body representations while observing others’ body parts

The way human bodies are represented is central in everyday activities. The cognitive system must combine internal, visceral, and somatosensory, signals to external, visually driven information generated from the spatial placement of others’ bodies and the own body in the space. However, how different body representations covertly interact among them when observing human body parts is still unclear. Therefore, we investigated the implicit processing of body parts by manipulating either the body part stimuli’ posture (conditions a and b) or the participants’ response body posture (conditions c, d, and e) in healthy participants (N = 70) using a spatial compatibility task called Sidedness task. The task requires participants to judge the colour of a circle superimposed on a task-irrelevant body part picture. Responses are facilitated when the spatial side of the responding hand corresponds to the spatial code generated by the hand stimulus's position with respect to a body of reference. Results showed that the observation of the task-irrelevant body parts oriented participants’ attention and facilitated responses that were spatial compatible with the spatial position such body parts have within a configural representation of the body structure (i.e., Body Structural Representation) in all the five experimental conditions. Notably, the body part stimuli were mentally attached to the body according to the most comfortable and less awkward postures, following the anatomo-physiological constraints. Moreover, the pattern of the results was not influenced by manipulating the participants’ response postures, suggesting that the automatic and implicit coding of the body part stimuli does not rely on proprioceptive information about one's body (i.e., Body Schema). We propose that the human body's morphometry knowledge is enriched by biomechanical and anatomo-physiological information about the real body movement possibilities. Moreover, we discuss the importance of the automatic orienting of attention based on the sidedness within the context of imitational learning.