A procedure in which responses reduced intermittently presented electric shocks to one quarter of their originally scheduled intensity, effectively engendered and maintained lever pressing in hooded rats. This contingency also markedly increased the response rates of rats initially trained under an unsignaled avoidance procedure. The responding of all animals extinguished rapidly when shock was withdrawn. Subsequently, it was discovered that high response rates could be maintained solely through presentation of shocks that were not affected by responses. Variations in the interval between shocks and changes in shock intensity over a wide range did not attenuate responding. Terminal performance was characterized by a consistent pattern of shock-elicited responses. Responses were also elicited by a tone following repeated tone-shock pairings. Finally, responding that was maintained by response-independent shocks was quickly suppressed by response-contingent shocks of the same intensity.

Journal Article↗

PubMed1969

Running-wheel activity and avoidance in the mongolian gerbil.

In the first of two experiments, running-wheel activity and unsignaled (Sidman) avoidance were studied in gerbils and albino rats. All gerbils ran at higher rates than any of the four rats studied. Under the avoidance procedure, four rats developed effective responding; the other two performed much less successfully. While avoidance developed more slowly in the gerbils, all showed asymptotic performance as effective as the four superior rats. The rats showed a consistent warm-up effect, receiving 60% to 80% of the total shocks in the initial third of the session. The gerbils displayed no warm-up, with shocks being evenly distributed over the session. Warm-up in the rats was not related to either response rate or to how effectively the animal was avoiding. When shock was removed, extinction occurred more rapidly in the rats than the gerbils. In the second experiment, which involved two-way shuttle avoidance, gerbils and albino mice quickly acquired the response. All animals met a criterion of 90% avoidance over 80 trials.

Journal Article↗

PubMed1968

Granuloma inguinale.

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Adult↗

PubMed1967

Laser radiation: some specific dental effects and an evaluation of its potential in dentistry.

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Birefringence↗

PubMedDate not supplied

Mandibular lateral incisor-canine transposition in monozygotic twins.

Mandibular tooth transposition, involving the right lateral incisor and canine, is described in monozygotic twin girls. This report provides evidence suggesting that genetic factors influence the development of mandibular lateral incisor-canine (Mn.I2.C) transposition. Interceptive orthodontic treatment for children with this rare occlusal abnormality should be considered.

Child↗