Sharing and Cooperation in Pigeons Results & Discussion, Part II Table Of Contents History Title Page List of Figures, Tables Introduction Purpose, Method Results and Discussion General Discussion References Abstract

Results and discussion

II. Free role-distribution

The results for the "free" role-distribution phase are summarized in Table 2. The results show (a) control of take responding by the differential reinforcement densities available in each response role (i.e., control by the programmed food reinforcement for the social behavior), and (b) social control of take responding, both of which are necessary in demonstrating sharing.

Take responding which occurred during trials in which both subjects engaged in take responding will be referred to as competitive take responding. Take responding which occurred during trials in which only one subject of a pair engaged in take responding will be referred to as individual take responding.

Take-response rate.

Figure 5 shows that the competitive take-response rate was higher during conditions in which food was not available for the follower at the end of the trial (no-foll-food conditions) than during conditions in which food was available for the follower at the end of the trial (foIl-food conditions) for one subject in each pair. The competitive take-response rates (no-foll-food/foll-food conditions) averaged 143-169/52-58 (P1S1) and 122/33-18 (P2S2) responses/minute.

Figure 5. Take responses per minute for individual end competitive leader-role takes during free distribution of response roles. Breaks in the x axis indicate absence of sessions during which equipment was intermittently failing.

Pair 1
Pair 2
Condition Description FF Follower Food Available NF No Follower Food Available

Figure 5 also shows that for the other subject of each pair (P1S2 and P2S1) there were no systematic changes in the competitive take-key response rates. There was also no systematic change in the individual-take response rate across conditions, with one exception. During the no-foll-food condition for pair two, the individual take-response rate of P2S2 rose from 93.7 to 135.2 responses/minute, then decreased to 72.2 responses/minute in the subsequent foil-food condition.

The differentiation of individual and competitive take-response rates within sessions for two subjects demonstrates control of take responding of the two subjects by the responding of the other subject. Control of the take responding by the food reinforcement rather than some unknown reinforcer (cf. Daniel 1942; Daniel 1943; Marcucella and Owens, 1975) is demonstrated by the differential in competitive take-response rates between the foll-food and no-foll-food conditions for the same two subjects (P1S1 and P2S2). However, the take-response rate data leaves a question as to the sources of control of the take responding of the other two subjects (P1S2 and P2S1), a question answered by the take-response latency data.

Take-response latency.

Figure 6 shows that the competitive-take response latencies were shorter than the individual-take response latencies across no-foll-food and foll-food conditions for all but one subject (P2S1). Take-response average latencies (competitive/individual) across conditions were 1.4-2.1/5.3-9.5 (P1S1), 2.1-5.1/9.4-12.5 (P1S2), 2.7-7.8/6.619.8 (P2S1), and 1.8-4.4/7.7-14.6 (P2S2) seconds. If latencies are compared within conditions, the competitive-take latencies were shorter for all subjects within all conditions.

Figure 6. Take response latencies for individual and competitive leader-role takes during free distribution of response roles. Breaks in the x axis indicate absence of sessions during which equipment was intermittently failing.

Pair 1
Pair 2
Condition Description FF Follower Food Available NF No Follower Food Available

The latencies of competitive-take responding for all but one subject (PIS1) were shorter during the no-foll-food conditions then during the foll-food conditions. Average competitive take-response latencies (no-foll-food/foll-food) were 1.4-1.5/1.6-2.1 (P1S1), 2.1-2.4/3.5-5.1 (P1S2), 2.7/7.1-7.6 (P2S1), and 1.8/3.8-4.3 (P2S2) seconds.

The one subject (P1S1) that did not respond with a shorter competitive-take latencies during no-foll-food conditions was one of the two subjects that did show a systematic change in the rate of competitive-take responding across conditions. The differentiation of individual and competitive take-response latencies within sessions for three subjects demonstrates control of the take responding of the three subjects (P1S2, P2S1, and P2S2) by the responding of the other subject. Control of the take responding by the food reinforcement rather then some unknown reinforcer is demonstrated by the differential in competitive take-response latencies between the foll-food and no-foll-food conditions for the same three subjects. The take-response latency data taken along with the take-response rate data demonstrate social control of food reinforced take responding for all four subjects in the study.

Percentage of trials with competitive take responding.

Figure 7 shows that given the opportunity to compete, the percentage of trials on which competitive takes (vs. individual takes) occurred was higher for both pairs of subjects during no-foll-food conditions than during foll-food conditions. Competitive takes occurred on an average of (no-foll-food/foll-food conditions) 33-42%/8-15% and 28%/7-11% of the trials per session, for pair one (P1) and pair two (P2) respectively.

Figure 7. Opportunities to compete per session and percentage of opportunities to compete on which competitive takes occurred during free distribution of response roles. Breaks in the x axis indicate absence of sessions during which equipment was intermittently failing.

Condition Description FF Follower Food Available NF No Follower Food Available

In order to demonstrate a sharing effect, the proportion of trials on which subjects compete must decrease (Hake, Vukelich, and Olvera, 1975). The proportion of trials, on which competition occurred did not decrease significantly for either pair during the conditions in which the shift from competition to sharing was to be expected (i.e., the no-foIl-food conditions). Hence, a sharing effect was not demonstrated in this study.

Distribution of reinforcements between subjects.

Figure 8 shows the distribution of the reinforcements occurring per session for each pair. In the foil-food conditions, the percentage is based on the total reinforcements occurring in both response roles; in no-foll-food conditions, the percentage is based on reinforcements occurring in the leader role (i.e., no reinforcement occurred in the follower component). One subject in each pair averaged over 50% of the reinforcements per session. Which subject took the larger share varied systematically across conditions. The subject in each pair which responded at the higher take response rate within a trial during no-foll-food conditions (see take-response rate, above) was the subject receiving the larger share of reinforcements during no-foil-food conditions. The subject in each pair that received over half the reinforcements during no-foll-food conditions was also the subject that received less than half the reinforcements during foll-food conditions. In pair one, P1S1 received (no-foll-food/foll-food) 63.4-59.7%/47.8-48.2% of the reinforcements per session; in pair two P2S2 60.6%/44.1-48.5% of the reinforcements per session.

Figure 8. Distribution of food reinforcements between subjects of a pair during free distribution of response roles. Breaks in the x axis indicate absence of sessions during which equipment was intermittently failing.

Condition Description FF Follower Food Available NF No Follower Food Available

Leader and follower response accuracy.

Figure 9 shows percentage of trials on which subjects made the appropriate matching response for each the leader (color matching) and follower (social matching) response roles. All subjects made the appropriate matching response on 89.0% (89.0-98.3%) or more trials as leader. Follower responding varied systematically across conditions. Subjects responded with about the same degree of accuracy as follower during loll-food conditions as they did as leader during all conditions (83.8%-96.5%). During no-foll-food conditions subjects engaged in social-matching responding on between 48.5-79.8% of trials in the follower response role.

Figure 9. Matching percent correct for leader and follower responding during free distribution of response roles. Breaks in the x axis indicate absence of sessions during which equipment was intermittently failing.

Pair 1
Pair 2
Condition Description FF Follower Food Available NF No Follower Food Available