Indexador

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Conditioning techniques were developed demonstrating that pure tone frequencies under water can exert nearly perfect control over the underwater click vocalizations of the California sea lion (Zalophus californianus). Conditioned vocalizations proved to be a reliable way of obtaining underwater sound detection thresholds in Zalophus at 13 different frequencies, covering a frequency range of 250 to 64,000 Hz. The audiogram generated by these threshold measurements suggests that under water, the range of maximal sensitivity for Zalophus lies between one and 28 kHz with best sensitivity at 16 kHz. Between 28 and 36 kHz there is a loss in sensitivity of 60 dB/octave. However, with relatively intense acoustic signals (> 38 dB re 1 μb underwater), Zalophus will respond to frequencies at least as high as 192 kHz. These results are compared with the underwater hearing of other marine mammals.

Detailed descriptive data are provided on the free‐operant avoidance behavior of rats in a shuttlebox during both acquisition and terminal performance. Initially, eighteen 21‐min acquisition sessions were given. Each hurdle‐cross postponed the next shock 20 sec (response‐shock interval) and shocks were scheduled every 5 sec (shock‐shock interval) in the absence of a response. All eight subjects avoided over 70% of the shocks due (12/min) in Session 1. Maximum response rates were reached by the third session and declined slowly while shock rates continued to drop slowly through Session 15. Three subjects were run an additional five months with a response‐shock interval of 20 sec and their terminal response rates were all under five responses per minute and shock rates were 0.07 per minute. Interresponse time distributions for terminal performance showed that over 95% of all responding by all three subjects occurred in the last half of the response‐shock interval.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Key pecking of pigeons under a fixed‐ratio 100, grain reinforcer schedule was followed by electric shock occurring once in each sequence of 100 responses with the shocked response varying irregularly in successive sequences. Under this shock schedule, a localized suppression of responding in a response sequence was not correlated with the probability of shock at different points in the sequence. High shock levels increased the duration of post‐reinforcement pauses and suppressed responding during the first half of the response sequence. This suppression often persisted after the shocked response when shock occurred early in the sequence. The shock schedule did not produce a consistent suppressing effect on responding during the last half of the response sequence.