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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 22, Issue 2, 2009

Research Paper

Pigeons, Rats, and Humans Show Analogous Misinformation

In three experiments, we show that pigeons, rats and humans can be influenced by misleading postevent information in ways analogous to findings in the human memory distortion literature. We used a delayed matching to sample analog of the eyewitness testimony procedure from Loftus et al.(1978), and varied the length of the delay between event and exposure to post event information(PEI). We also varied the nature of PEI so that it was consistent with the event information, inconsistent, or neutral. In Experiment 1, pigeons’ memory performance for colored lights was influenced by the presence of another colored light. In Experiment 2, rats’ memory performance for lever position was influenced by position-related cue lights. In Experiment 3, we verified the validity of our analog procedure by having human subjects remember kaleidoscope images. Despite differences in species and the nature of the stimuli, all three experiments replicated key findings in the literature: memory accuracy was highest when consistent PEI was presented at the end of a delay, and lowest when inconsistent PEI presented at the end of a delay interval. PEI had no effect when presented at the beginning of a delay.

Individual Recognition in Japanese Quail Requires Physical and Behavioral Cues

Individual recognition is a complex social learning process in which idiosyncratic characteristics of a conspecific are learned and later used to discriminate this conspecific from others. Many social species of birds appear to be capable of individual recognition. However, it is possible that at least under some circumstances these and other species discriminate conspecifics not based on individual recognition but instead, by recognizing them as members of one or more social categories. Many references to individual recognition in the literature have neglected to address this distinction. For example, Riters and Balthazart (1998) reported that male quail were capable of recognizing individual females with which they had and had not copulated, but their experimental design may have unintentionally created two social categories of females (sexually receptive and non-receptive). The present set of experiments replicated Riters’ and Balthazart’s findings (Experiment 1) and then tested male quail for their ability to recognize females based on physical cues only (Experiment 2), physical and behavioral cues (Experiment 3), and the social categorization cues associated with female receptivity (Experiment 4). The results suggested that male quail are capable of recognizing individual females with which they have and have not copulated, but this recognition is not based onphysical, non-sexual, or sexual receptivity behaviors in isolation. Instead, individual recognition occurred only when the males were able to utilize all of these potentially distinctive female attributes in combination. The results also suggested that female receptivity responses may be unique and idiosyncratic, varying along one or more dimensions.

Magnitude Effects of Sexual Reinforcement in Japanese Quail

The effect of the magnitude of sexual reinforcement on the extinction of a running response was studied in quail. In Experiment 1, a group of subjects (L) received copulatory access to eight females, whereas a second group (S) received access to a single female. Both groups acquired the running response. During extinction, Group S showed a fast decrease in responding, whereas Group L persisted longer. In Experiment 2, males were allowed a choice between one or eight females. Preference for eight females demonstrated that males discriminated between the two reward magnitudes and that access to eight females had a larger reinforcing value than access to one female. The results are discussed within the context of the paradoxical reinforcement effects and the divergence in learning mechanisms in birds.