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.     

Manifestations, acquisition and diagnostic categories of dental fear in a self-referred population

This study aimed to clarify how manifestations and acquisition relate to diagnostic categories of dental fear in a population of self-referred dental fear patients, since diagnostic criteria specifically related to dental fear have not been validated. DSM III-R diagnostic criteria for phobias were used to compare with four existing dental fear diagnostic categories, referred to as the Seattle system. Subjects were 208 persons with dental fear who were telephone interviewed, of whom a subsample of 155 responded to a mailed Dental Anxiety Scale (DAS), State-Trait Anxiety Inventory and a modified FSS-II Geer Fear Scale (GFS). Personal interviews and a Dental Beliefs Scale of perceived trust and social interaction with dentists were also used to evaluate a subsample of 80 patients selected by sex and high dental fear. Results showed that the majority of the 80 patients (66%), suffered from social embarrassment about their dental fear problem and their inability to do something about it. The largest cause of their fear (84%) was reported to be traumatic dental experiences, especially in childhood (70%). A minority of patients (16%) could not isolate traumatic experiences and had a history of general fearfulness or anxiety. Analysis of GFS data for the 155 subjects showed that fear of snakes and injuries were highest among women; heights and injections among men. Fear of blood was rarely reported. Spearman correlations between GFS individual items and DAS scores indicated functional independence between dental fear and common fears such as blood, injections and enclosures in most cases. Only in specific types of dental fear did these results support Rachman and Lopatka's contention that fears are thought to summate.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Anxiety induced by cardiac perceptions in patients with panic attacks: a field study

In panic disorder bodily sensations appear to play an important role as a trigger for anxiety. In our psychophysiological model of panic attacks we postulate the following vicious circle: individuals with panic attacks perceive even quite small increases in heart rate and interpret these changes as being catastrophic. This elicits anxiety and a further increase in heart rate. To evaluate this model we conducted a field study of 28 subjects with panic attacks and 20 healthy controls. A 24 hr ambulatory ECG was recorded and the subjects were instructed to report any cardiac perceptions during this period and to rate the anxiety elicited by these perceptions. The incidence of cardiac perceptions was about the same in both groups, but only subjects with panic attacks reported anxiety associated with such perceptions. Analysis of the ECGs revealed that in both groups heart rate accelerations preceded cardiac perceptions. Following cardiac perceptions, the healthy controls showed a heart rate deceleration, whereas the subjects with panic attacks had a further acceleration. This heart rate increase after cardiac perceptions was positively related to the level of anxiety elicited by the perceptions. These results provide clear evidence in support of the vicious circle model of panic attacks.     

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.     

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.