U-shaped learning and frequency effects in a multi-layered perceptron: implications for child language acquisition

A three-layer back-propagation network is used to implement a pattern association task in which four types of mapping are learned. These mappings, which are considered analogous to those which characterize the relationship between the stem and past tense forms of English verbs, include arbitrary mappings, identity mappings, vowel changes, and additions of a suffix. The degree of correspondence between parallel distributed processing (PDP) models which learn mappings of this sort (e.g., Rumelhart & McClelland, 1986, 1987) and children's acquisition of inflectional morphology has recently been at issue in discussions of the applicability of PDP models to the study of human cognition and language (Pinker & Mehler, 1989; Bever, in press). In this paper, we explore the capacity of a network to learn these types of mappings, focusing on three major issues. First, we compare the performance of a single-layered perceptron similar to the one used by Rumelhart and McClelland with a multi-layered perceptron. The results suggest that it is unlikely that a single-layered perceptron is capable of finding an adequate solution to the problem of mapping stems and past tense forms in input configurations that are sufficiently analogous to English. Second, we explore the input conditions which determine learning in these networks. Several factors that characterize linguistic input are investigated: (a) the nature of the mapping performed by the network (arbitrary, suffixation, identity, and vowel change); (b) the competition effects that arise when the task demands simultaneous learning of distinct mapping types; (c) the role of the type and token frequency of verb stems; and (d) the influence of phonological subregularities in the irregular verbs. Each of these factors is shown to have selective consequences on both successful and erroneous performance in the network. Third, we outline several types of systems which could result in U-shaped acquisition, and discuss the ways in which learning in multi-layered networks can be seen to capture several characteristics of U-shaped learning in children. In general, these models provide information about the role of input in determining the kinds of errors that a network will produce, including the conditions under which rule-like behavior and U-shaped learning will and will not emerge. The results from all simulations are discussed in light of behavioral data on children's acquisition of the past tense and the validity of drawing conclusions about the acquisition of language from models of this sort.     

Visual palatability of food in patients with eating disorders and dieting women

The effects of 19 meals of different caloric content on slides on palatability and hypothetical duration of consumption were investigated in 7 patients with anorexia nervosa, 17 patients with bulimia nervosa at the beginning and after 8 weeks of hospital treatment. Nine healthy females served as controls. At the beginning of treatment, palatability of low caloric food was significantly higher and hypothetical duration of consumption of high caloric food was significantly longer in patients when compared to controls. After 8 weeks, in the patients palatability of low caloric food had decreased. Dislike for high caloric food remained stable in anorexics.     

What children can tell us about living in danger

Developmental challenges faced by children growing up in situations of chronic danger linked to community violence and communal conflict are reviewed. The concept of post-traumatic stress disorder is expanded to include situations of chronic and on-going traumatic stress associated with dangerous environments--war zones and inner city neighborhoods plagued by violence and crime. Of particular importance is the impact of chronic stress and danger on the child's world view, the child's social map, and the child's moral development. On the basis of field work in 5 war zones, the article points to the importance of adult-led "processing" of the young child's experience to his or her psychological coping and moral development. Some of the contradictions operating in such environments are explored--for example, that "fanatical" ideology may provide short-term support for adults and children but also may serve to prolong communal conflict, impede the necessary processing of experience, and increase vulnerability in the long run.     

Multiple role juggling and daily mood states in working mothers: an experience sampling study

The effects of multiple role juggling (i.e., simultaneously attending to demands of different roles) on daily mood states of employed mothers were examined. Ss completed activity and mood questionnaires 8 times a day for 8 days. Multiple role juggling had immediate negative effects on task enjoyment and mood. However, contrast effects and habituation to role juggling occurred when mood and satisfaction were examined over time. Furthermore, mood states tended to spill over from one episode to the next within a day, but contrast effects were found across days. These results reflect the complex nature of psychological adjustment to multiple role occupancy.     

The relation of perception and motor action: ideomotor compatibility and interference in divided attention

Ideomotor theory is one variation of the general position that perception and motor action are related. According to this theory, a perceptual representation of the goal of a response must be generated prior to response initiation. Ideomotor theory can be extended by assuming that generation of this representation, which usually is required prior to motor action, is not needed if the stimulus itself corresponds to the response goal, that is, if the stimulus and response are ideomotor compatible. Because processing to generate the response representation is not needed with ideomotor compatibility, it should be possible to control two responses simultaneously without mutual interference if at least one stimulus-response relation is ideomotor compatible. Although supported in previous work involving discrete responses, this prediction of perfect time-sharing was found not to hold in the experiments reported here. These experiments, unlike those showing perfect time-sharing, involved continuous responses. We propose an alternative version of ideomotor compatibility, in which perfect time-sharing can occur if an integrated stimulus is provided to match the continuous and integrated response.     

Strategy changes in human contingency judgments as a function of contingency tables.

Judgment strategies of 169 undergraduate students on problems to judge the contingency between two binary events were identified by the method of rule-based analysis to clarify whether or not the strategies the subjects used would be affected by the concrete nature of the contingency table. Problems were constructed along two factors: total cell frequency and width of range of objective contingencies. Although the factor of total cell frequency had no effect on subjects' strategies, the number of subjects who changed strategies corresponding with problem instances increased when the objective contingencies were set closer to zero or when problems became more difficult. These results are discussed in the context of previous studies of this issue in the literature.     

An examination of the construct validity of the Social Anhedonia Scale

Two studies bearing on the construct validity of the Social Anhedonia Scale (SA) are reported. Study 1 reported convergent validity coefficients between the SA scale and numerous measures of traits reflecting a generalized attitude toward others (e.g., social interest and empathy) as well as several traits reflecting maladjustment without a social component as a test of discriminant validity (e.g., pessimism and rigidity). Study 1 found impressive convergent validity for the SA scale and mixed discriminant validity. Study 2 found that the SA scale was related to two dimensions of striving for security, one of which is strongly influenced by negative interpersonal tendencies, suggesting support for the validity of the SA scale. Implications for the measurement and concept of social anhedonia are presented.     

The perceived causal structure of loneliness

Two studies examined the way people represent the causes of loneliness as a semantic space and as a causal network. In a multidimensional scaling task, the results of Michela, Peplau, and Weeks (1982) were replicated and the causes wee classified according to locus and stability. In a 2nd study, 44 people judged the likelihood that these causes were interconnected. From these data, a causal network or perceived causal structure (Kelley, 1983) was derived by means of network analysis. The structure revealed a complex lay theory of loneliness in which personality influenced group behavior, which in turn influenced psychological states and beliefs. States and beliefs were also affected by physical features and situational factors.