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Thor, D. H., & Holloway, W. R. (1982). Social memory of the male laboratory rat. J. Comp. Physiol. Psychol., 96(6), 1000–1006.
Abstract: Used duration of social-investigatory behavior by 36 mature male Long-Evans rats as a measure of individual recognition in 5 experiments to assess social memory. In Exp I, the duration of social investigation during a 2nd exposure to the same juvenile (n[en space]=[en space]12) was directly related to the length of the interexposure interval. In Exp II, Ss were exposed to the same or different juvenile 10 min after an initial 5-min exposure to a novel juvenile; reexposure to the same juvenile elicited significantly less social investigation than an exposure to a different juvenile. Exps III and IV demonstrated that following a 5-min introductory exposure, social memory of the juvenile was relatively brief in comparison with that of mature Ss. Exp V revealed a retroactive interference effect on recently acquired memory for an individual: 12 mature Ss exposed to interpolated social experience engaged in significantly longer investigation of a juvenile than those with no interpolated social experience. The combined results suggest that (1) the rat normally engages in spontaneous learning of individual identity and (2) social memory may be a significant aspect of complex social interactions. (16 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)
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Urcuioli, P. J., & Zentall, T. R. (1986). Retrospective coding in pigeons' delayed matching-to-sample. J Exp Psychol Anim Behav Process, 12(1), 69–77.
Abstract: In this study we examined how coding processes in pigeons' delayed matching-to-sample were affected by the stimuli to be remembered. In Experiment 1, two groups of pigeons initially learned 0-delay matching-to-sample with identical comparison stimuli (vertical and horizontal lines) but with different sample stimuli (red and green hues or vertical and horizontal lines). Longer delays were then introduced between sample offset and comparison onset to assess whether pigeons were prospectively coding the same events (viz., the correct line comparisons) or retrospectively coding different events (viz., their respective sample stimuli). The hue-sample group matched more accurately and showed a slower rate of forgetting than the line-sample group. In Experiment 2, pigeons were trained with either hues or lines as both sample and comparison stimuli, or with hue samples and line comparisons or vice versa. Subsequent delay tests revealed that the hue-sample groups remembered more accurately and generally showed slower rates of forgetting than the line-sample groups. Comparison dimension had little or no effect on performance. Together, these data suggest that pigeons retrospectively code the samples in delayed matching-to-sample.
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Dougherty, D. M., & Lewis, P. (1991). Stimulus generalization, discrimination learning, and peak shift in horses. J Exp Anal Behav, 56(1), 97–104.
Abstract: Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.
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Urcuioli, P. J., & Zentall, T. R. (1992). Transfer across delayed discriminations: evidence regarding the nature of prospective working memory. J Exp Psychol Anim Behav Process, 18(2), 154–173.
Abstract: Pigeons were trained successively either on 2 delayed simple discriminations or on a delayed simple discrimination followed by delayed matching-to-sample. During subsequent transfer tests, the initial stimuli from the 1st task were substituted for those in the 2nd. Performances transferred immediately if both sets of initial stimuli had been associated with the presence versus absence of food on their respective retention tests, and the direction of transfer (positive or negative) depended on whether the substitution involved stimuli with identical or different outcome associates. No transfer was found, however, when the initial stimuli were associated with different patterns of responding but food occurred at the end of every trial. These results are consistent with outcome expectancy mediation but are incompatible with response intention and retrospective coding accounts.
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Zentall, T. R., & Sherburne, L. M. (1994). Transfer of value from S+ to S- in a simultaneous discrimination. J Exp Psychol Anim Behav Process, 20(2), 176–183.
Abstract: Value transfer theory has been proposed to account for transitive inference effects (L. V. Fersen, C. D. L. Wynne, J. D. Delius, & J. E. R. Staddon, 1991), in which following training on 4 simultaneous discriminations (A+B-, B+C-, C+D-, D+E-) pigeons show a preference for B over D. According to this theory, some of the value of reinforcement acquired by each S+ transfers to the S-. In the transitive inference experiment, C (associated with both reward and nonreward) can transfer less value to D than A (associated only with reward) can transfer to B. Support for value transfer theory was demonstrated in 2 experiments in which an S- presented in the context of a stimulus to which responses were always reinforced (S+) was preferred over an S- presented in the context of a stimulus to which responses were sometimes reinforced (S +/-).
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Zentall, T. R., Roper, K. L., & Sherburne, L. M. (1995). Most directed forgetting in pigeons can be attributed to the absence of reinforcement on forget trials during training or to other procedural artifacts. J Exp Anal Behav, 63(2), 127–137.
Abstract: In research on directed forgetting in pigeons using delayed matching procedures, remember cues, presented in the delay interval between sample and comparisons, have been followed by comparisons (i.e., a memory test), whereas forget cues have been followed by one of a number of different sample-independent events. The source of directed forgetting in delayed matching to sample in pigeons was examined in a 2 x 2 design by independently manipulating whether or not forget-cue trials in training ended with reinforcement and whether or not forget-cue trials in training included a simultaneous discrimination (involving stimuli other than those used in the matching task). Results were consistent with the hypothesis that reinforced responding following forget cues is sufficient to eliminate performance deficits on forget-cue probe trials. Only when reinforcement was omitted on forget-cue trials in training (whether a discrimination was required or not) was there a decrement in accuracy on forget-cue probe trials. When reinforcement is present, however, the pattern of responding established during and following a forget cue in training may also play a role in the directed forgetting effect. These findings support the view that much of the evidence for directed forgetting using matching procedures may result from motivational and behavioral artifacts rather than the loss of memory.
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Kiltie, R. A., Fan, J., & Laine, A. F. (1995). A wavelet-based metric for visual texture discrimination with applications in evolutionary ecology. Math Biosci, 126(1), 21–39.
Abstract: Much work on natural and sexual selection is concerned with the conspicuousness of visual patterns (textures) on animal and plant surfaces. Previous attempts by evolutionary biologists to quantify apparency of such textures have involved subjective estimates of conspicuousness or statistical analyses based on transect samples. We present a method based on wavelet analysis that avoids subjectivity and that uses more of the information in image textures than transects do. Like the human visual system for texture discrimination, and probably like that of other vertebrates, this method is based on localized analysis of orientation and frequency components of the patterns composing visual textures. As examples of the metric's utility, we present analyses of crypsis for tigers, zebras, and peppered moth morphs.
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Crowley, P. H., Provencher, L., Sloane, S., Dugatkin, L. A., Spohn, B., Rogers, L., et al. (1996). Evolving cooperation: the role of individual recognition. Biosystems, 37(1-2), 49–66.
Abstract: To evaluate the role of individual recognition in the evolution of cooperation, we formulated and analyzed a genetic algorithm model (EvCo) for playing the Iterated Prisoner's Dilemma (IPD) game. Strategies compete against each other during each generation, and successful strategies contribute more of their attributes to the next generation. Each strategy is encoded on a `chromosome' that plays the IPD, responding to the sequences of most recent responses by the interacting individuals (chromosomes). The analysis reported in this paper considered different memory capabilities (one to five previous interactions), pairing continuities (pairs of individuals remain together for about one, two, five, or 1000 consecutive interactions), and types of individual recognition (recognition capability was maximal, nil, or allowed to evolve between these limits). Analysis of the results focused on the frequency of mutual cooperation in pairwise interactions (a good indicator of overall success in the IPD) and on the extent to which previous responses by the focal individual and its partner were associated with the partner's identity (individual recognition). Results indicated that a fixed, substantial amount of individual recognition could maintain high levels of mutual cooperation even at low pairing continuities, and a significant but limited capability for individual recognition evolved under selection. Recognition generally increased mutual cooperation more when the recent responses of individuals other than the current partner were ignored. Titrating recognition memory under selection using a fitness cost suggested that memory of the partner's previous responses was more valuable than memory of the focal's previous responses. The dynamics produced to date by EvCo are a step toward understanding the evolution of social networks, for which additional benefits associated with group interactions must be incorporated.
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Brodbeck, D. R. (1997). Picture fragment completion: priming in the pigeon. J Exp Psychol Anim Behav Process, 23(4), 461–468.
Abstract: It has been suggested that the system behind implicit memory in humans is evolutionarily old and that animals should readily show priming. In Experiment 1, a picture fragment completion test was used to test priming in pigeons. After pecking a warning stimulus, pigeons were shown 2 partially obscured pictures from different categories and were always reinforced for choosing a picture from one of the categories. On control trials, the warning stimulus was a picture of some object (not from the S+ or S- category), on study trials the warning stimulus was a picture to be categorized on the next trial, and on test trials the warning stimulus was a randomly chosen picture and the S+ picture was the warning stimulus seen on the previous trial. Categorization was better on study and test trials than on control trials. Experiment 2 ruled out the possibility that the priming effect was caused by the pigeons' responding to familiarity by using warning stimuli from both S+ and S- categories. Experiment 3 investigated the time course of the priming effect.
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Urcuioli, P. J., DeMarse, T. B., & Zentall, T. R. (1998). Transfer across delayed discriminations: II. Differences in the substitutability of initial versus test stimuli. J Exp Psychol Anim Behav Process, 24(1), 47–59.
Abstract: In 2 experiments, pigeons were trained on, and then transferred to, delayed simple discriminations in which the initial stimuli signalled reinforcement versus extinction following a retention interval. Experiment 1 showed that discriminative responding on the retention test transferred to novel test stimuli that had appeared in another delayed simple discrimination but not to stimuli having the same reinforcement history off-baseline. By contrast, Experiment 2 showed that performances transferred to novel initial stimuli whether they had been trained on-baseline or off-baseline. These results suggest that the test stimuli in delayed simple discriminations acquire control over responding only in the memory task itself. On the other hand, control by the initial stimuli, if coded as outcome expectancies, does not require such task-specific training.
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