. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 586 M. K. POWERS AND R. B. BARLOW, JR. extinction trials. As Figure 4 shows, extinction of the conditioned response to light was rapid and complete after the shock was turned off. Figure 5 shows psychometric functions for animal L9 tested with white light during the day (open circles) and at night (filled circles). It illustrates three characteristic features of Limulus performance during testing in the conditioning paradigm. First, the animals did not always respond to lights that were clearly above threshold (, from lo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 586 M. K. POWERS AND R. B. BARLOW, JR. extinction trials. As Figure 4 shows, extinction of the conditioned response to light was rapid and complete after the shock was turned off. Figure 5 shows psychometric functions for animal L9 tested with white light during the day (open circles) and at night (filled circles). It illustrates three characteristic features of Limulus performance during testing in the conditioning paradigm. First, the animals did not always respond to lights that were clearly above threshold (, from log I = — to — in Fig. 5); most conditioned animals responded to an average of only 60 to 70% of such stimuli during testing. This property did not differ between day and night conditions. Second, an intensity was nearly always found to which the animals would not respond (log I = — at night and log I = — during the day in Fig. 5). And third, intensities could be found that elicited a reliable response during the night but not during the day (, log I = in Fig. 5). The threshold of animal L9 was lower at night than during the day. We estimated the difference in sensitivity between day and night to be log units by shifting the illustrated curves along the abscissa until the best fit was achieved by eye. Figure 6 illustrates the inter-observer reliability of our scoring technique. The chart records for the data in Figure 5 were separately scored during the experiment by MP who knew the intensity of the stimulus and after the experiment by RB who did not. The two sets of scorings were similar with a high statistical correlation (r = .79, P < .0001 for daytime data and r = .64, P < .005 for nighttime data). The average of our two scorings was used to construct Figure 5. All other figures were constructed from scorings of one observer. Figure 7 shows a decrease in threshold at night when conditioned animals were tested with monochromatic lig
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
