Neural Network Simulation of Infant Familiarization to Artificial Sentences: Rule-Like Behavior Without Explicit Rules and Variables

A fundamental issue in cognitive science is whether human cognitive processing is better explained by symbolic rules or by subsymbolic neural networks. A recent study of infant familiarization to sentences in an artificial language seems to have produced data that can only be explained by symbolic rule learning and not by unstructured neural networks (Marcus, Vijayan, Bandi Rao, & Vishton, 1999). Here we present successful unstructured neural network simulations of the infant data, showing that these data do not uniquely support a rule-based account. In contrast to other simulations of these data, these simulations cover more aspects of the data with fewer assumptions about prior knowledge and training, using a more realistic coding scheme based on sonority of phonemes. The networks show exponential decreases in attention to a repeated sentence pattern, more recovery to novel sentences inconsistent with the familiar pattern than to novel sentences consistent with the familiar pattern, occasional familiarity preferences, more recovery to consistent novel sentences than to familiarized sentences, and extrapolative generalization outside the range of the training patterns. A variety of predictions suggest the utility of the model in guiding future psychological work. The evidence, from these and other simulations, supports the view that unstructured neural networks can account for the existing infant data.

Correlation of in vitro susceptibilities to newer quinolones of naturally occurring quinolone-resistant Neisseria gonorrhoeae strains with changes in GyrA and ParC

The in vitro activities of ciprofloxacin, trovafloxacin, moxifloxacin, and grepafloxacin against 174 strains of Neisseria gonorrhoeae isolated in Sydney, Australia, were determined. The strains included 84 quinolone-less-sensitive and -resistant N. gonorrhoeae (QRNG) strains for which ciprofloxacin MICs were in the range of 0.12 to 16 microg/ml. The QRNG included strains isolated from patients whose infections were acquired in a number of countries, mostly in Southeast Asia. The gyrA and parC quinolone resistance-determining regions (QRDR) of 18 selected QRNG strains were sequenced, and the amino acid mutations observed were related to the MICs obtained. The activities of moxifloxacin and grepafloxacin against QRNG were comparable to that of ciprofloxacin. Trovafloxacin was more active than the other quinolones against some but not all of the QRNG strains. Increments in ciprofloxacin resistance occurred in a step-wise manner with point mutations initiated in gyrA resulting in amino acid alterations Ser91-to-Phe, Ser91-to-Tyr, Asp95-to-Gly, and Asp95-to-Asn. Single gyrA changes correlated with ciprofloxacin MICs in the range 0.12 to 1 microg/ml. The Ser91 changes in GyrA were associated with higher MICs and further QRDR changes. QRNG strains for which ciprofloxacin MICs were greater than 1 microg/ml had both gyrA and parC QRDR point mutations. ParC alterations were seen in these isolates only in the presence of GyrA changes and comprised amino acid changes Asp86-to-Asn, Ser87-to-Asn, Ser87-to-Arg, Ser88-to-Pro, Glu91-to-Lys, and Glu91-to-Gln. QRNG strains for which MICs were in the higher ranges had double GyrA mutations, but again only with accompanying ParC alterations. Not only did the nature and combination of GyrA and ParC changes influence the incremental increases in ciprofloxacin MICs, but they seemingly also altered the differential activity of trovafloxacin. Our findings suggest that the newer quinolones of the type examined are unlikely to be useful replacements for ciprofloxacin in the treatment of gonorrhea, particularly where ciprofloxacin MICs are high or where resistance is widespread.

The learning of first and second person pronouns in English: network models and analysis

Although most English-speaking children master the correct use of first and second person pronouns by three years, some children show persistent reversal errors in which they refer to themselves as you and to others as me. Recently, such differences have been attributed to the relative availability of overheard speech during the learning process. The present study tested this proposal with feed-forward neural networks learning these pronouns. Network learning speed and analysis of their knowledge representations confirmed the importance of exposure to shifting reference provided by overheard speech. Errorless pronoun learning was linked to the amount of overheard speech, interactions with a greater number of speakers, and prior knowledge of the basic-level kind PERSON.

Neural network modeling of developmental effects in discrimination shifts

This paper presents neural network simulations of developmental phenomena in discrimination shifts. The discrimination shift literature is reviewed in order to identify the empirical regularities. Leading theoretical accounts of the development of shift learning are reviewed, and the lack of a thorough account is highlighted. Recent unsuccessful neural network simulations of shift learning are also reviewed. New simulations, using the cascade-correlation algorithm, show that networks can capture the regularities of the discrimination shift literature better than existing psychological theories. Manipulation of the amount of training that networks receive, which affects depth of learning, simulates developmental phenomena. It is suggested that human developmental differences in shift learning arise from spontaneous overtraining by older participants, an interpretation consistent with the overtraining literature.

Failure of azithromycin therapy in gonorrhea and discorrelation with laboratory test parameters

BACKGROUND

Azithromycin is efficacious in the treatment of chlamydial genital tract infection but less so in gonorrhea. However, MICs of azithromycin for gonococci from previously reported azithromycin treatment failures were consistently below the 'susceptible' MIC level of 2 mg/L.

GOAL OF THIS STUDY

To examine gonococci not eliminated with 1 g azithromycin therapy to establish treatment outcome/MIC correlates in gonorrhea.

STUDY DESIGN

The MICs and phenotypes of gonococci isolated from five cases of treatment failure after 1 g azithromycin therapy were determined and compared with the MICs of a systematic sample of routine isolates.

RESULTS

Azithromycin MICs of gonococci from five cases of failed 1 g azithromycin treatment were 0.125 or 0.25 mg/L, well within the current 'susceptible' MIC range. None of the isolates were of the mtr phenotype. The MIC90 of a systematic sample of 219 gonococcal isolates was 0.25 mg/L.

CONCLUSION

The antibiotic MIC/treatment outcome correlates that are usually found in gonorrhea do not apply for azithromycin. Current MIC criteria do not accurately define susceptibility or resistance of gonococci to azithromycin and by themselves do not predict the likely outcome of therapy. Pharmacokinetic factors may decrease the predictive value of MIC data.

Continuing evolution of the pattern of quinolone resistance in Neisseria gonorrhoeae isolated in Sydney, Australia

BACKGROUND AND OBJECTIVES

Multiple phenotypes of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney since 1984 originated in Asia and increased in number and level of resistance in 1995.

GOAL

To study the origins, characteristics, and infection pattern of quinolone-resistant Neisseria gonorrhoeae in Sydney from 1995 to 1997 and to compare these results with prior findings.

STUDY DESIGN

Quinolone minimal inhibitory concentrations, phenotype, and geographic source of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney from 1995 to 1997 were analyzed.

RESULTS

Two hundred nineteen episodes of infection with quinolone-resistant Neisseria gonorrhoeae from 2,236 gonococcal isolates occurred during 1995 through 1997. The rate of isolation of quinolone-resistant Neisseria gonorrhoeae increased significantly at the end of 1996 and was maintained through 1997. The increase resulted from sustained domestic transmission of a limited number of phenotypes in heterosexual patients.

CONCLUSION

The pattern of isolation of quinolone-resistant Neisseria gonorrhoeae in Sydney changed from the sporadic isolation of multiple phenotypes of imported quinolone-resistant Neisseria gonorrhoeae to a higher rate of endemic disease caused by a few subtypes. Alterations in antibiotic treatment regimens in the affected patient group were required.

Quinolone-resistant Neisseria gonorrhoeae isolated in Sydney, Australia, 1991 to 1995

BACKGROUND AND OBJECTIVES

Quinolone antibiotics are used widely for the treatment of gonorrhea, but resistant strains appeared in Sydney in 1984, treatment failure with high-dose regimens in 1991, and isolates with very high minimal inhibitory concentrations (MICs) (16 mg/l) in 1994.

GOALS

To examine the frequency, source, and characteristics of Quinolone-resistant Neisseria gonorrhoeae (QRNG) in Sydney from 1991 to 1995 and to compare these data with those obtained from 1984 to 1990.

STUDY DESIGN

The antibiotic sensitivity, auxotype-serovar class, and geographic source of QRNG isolated in Sydney from January 1, 1991 to June 30, 1995 were analyzed.

RESULTS

One hundred seven QRNG were isolated from 97 patients from 1991 to 1995. The number, proportion, and MICs of QRNG increased slowly in the first 4 years of the study and rapidly in the last 6 months. Most QRNG were isolated from travelers entering Sydney from Asia. Twenty-seven different auxotype-serovar classes were detected including 6 auxotype-serovar classes in 14 isolates with high-level quinolone resistance (MIC, 16 mg/l).

CONCLUSIONS

QRNG isolated in Sydney during the past decade originated in Asia as multiple gonococcal subtypes and increased substantially in numbers and levels of resistance in 1995.

Cognitive dissonance reduction as constraint satisfaction

A constraint satisfaction neural network model (the consonance model) simulated data from the two major cognitive dissonance paradigms of insufficient justification and free choice. In several cases, the model fit the human data better than did cognitive dissonance theory. Superior fits were due to the inclusion of constraints that were not part of dissonance theory and to the increased precision inherent to this computational approach. Predictions generated by the model for a free choice between undesirable alternatives were confirmed in a new psychological experiment. The success of the consonance model underscores important, unforeseen similarities between what had been formerly regarded as the rather exotic process of dissonance reduction and a variety of other, more mundane psychological processes. Many of these processes can be understood as the progressive application of constraints supplied by beliefs and attitudes.

Strain characteristics and antibiotic susceptibility of isolates of Neisseria gonorrhoeae causing disseminated gonococcal infection in Australia. Members of the Australian Gonococcal Surveillance Programme

The auxotype (A) and serovar (S) distribution and antibiotic and serum sensitivity of 22 strains of Neisseria gonorrhoeae isolated from blood and joints were determined. With one exception, these strains from disseminated gonococcal infections (DGI) belonged to one of 4 serovars of the IA serogroup and were resistant to killing by normal human serum. The auxotype distribution of these Australian strains differed significantly from that reported elsewhere in that 17 of the 22 isolates were proline requires, but none were of the AHU auxotype. This lack of the AHU auxotype in the DGI strains in Australia was explained by the virtual absence of AHU requirers in a sample of 1560 mucosal strains isolated in Sydney and Darwin from 1987 to 1990. The A/S distribution of these mucosal isolates also helped to account for the low (0.12) percentage of DGI strains in isolates examined by the Australian Gonococcal Surveillance Programme (AGSP) from 1981 to 1991, and the differences in the rates of DGI in Sydney (0.08%) and Darwin (0.87%). There was a relative lack of the IA serogroup strains which are mostly responsible for DGI in the mucosal isolates from Sydney (15% of all strains) but a higher proportion of these serovars (40%) in the Darwin sample. There were 46 cases of DGI in data from the AGSP, 29 of these being women. Seven of the cases diagnosed in Australia were infected with penicillinase-producing gonococci suggesting that antibiotics other than the penicillins should now be used for this condition in this region.

Characteristics of Neisseria gonorrhoeae isolated in Australia showing decreased sensitivity to quinolone antibiotics

Forty three strains of Neisseria gonorrhoeae with decreased sensitivity to quinolone antibiotics were detected amongst 2141 Australian isolates of gonococci examined in the years 1984 to 1990. The strains examined belonged to 23 different auxotype/serovar classes, were generally more resistant to other antibiotics and, in the majority of cases, were isolated from travellers entering or returning to Australia from SE Asia. Quinolone-sensitive wild-type gonococci became less sensitive to these agents in vitro at a relatively high frequency when grown in the presence of quinolone concentrations at or around the MIC (Mean Inhibitory Concentration) of the antibiotic. Further increments in the levels of quinolone resistance of the already less-sensitive gonococci were also produced by this means, but high-level resistance to these agents was not observed. This suggests that mechanisms other than alterations in the DNA-gyrase of the organisms were responsible for the changes seen. Although spread of quinolone resistance in gonococci in Australia is unlikely to be rapid, if these antibiotics are used in therapy, treatment regimens with higher rather than lower dosages of quinolone antibiotics should be employed.

The infant's concept of agency: the distinction between social and nonsocial objects

The primary purpose of this study was to examine young infants' discrimination between the abilities of social and nonsocial objects to serve as agents. Thirty-one infants between 8 months and 8 days old and 14 months and 19 days old were studied. The children's communicative skills were evaluated through frustration episodes in which a toy was taken away in order to elicit communicative behaviors toward the mother. Visual fixation time was compared for events in which an inanimate object moved independently and events in which a human being was the agent. Analysis of the magnitude of decrease of attending responses revealed that the older infants took longer to process anomalous events, whereas the younger infants manifested more interest for events in which an animate being played the role of agent. The findings suggest that infants can distinguish between the causal powers of social and nonsocial objects by the end of the first year.

Maltose-negative Neisseria meningitidis isolated from a case of male urethritis

A maltose-negative strain of Neisseria meningitidis isolated from a male patient with urethritis was initially identified as a gonococcus on the basis of carbohydrate utilization tests. Additional investigations initiated because of atypical colony morphology and a negative superoxol reaction showed the isolate to be a meningococcus with defective maltose-phosphorylating capacity.