Six naive capuchin monkeys (Cebus appella) and six naive squirrel monkeys (Saimiri sciureus) were tested on an 8 second indirect delayed-response task in a modified Wisconsin General Test Apparatus (WGTA). Six experimental conditions were used to vary the lighting conditions during the 8 second delay between the termination of the 5 second cue light behind a door panel and the raising of a 2-way mirror screen which allowed the subject to respond to one of the two panels. These six conditions were altered by timers which controlled a small light located in the top of the test cage. The six experimental conditions were (1) light in test cage remained on for the entire 8 seconds; (2) light went off immediately following the termination of the cue light and remained off for the entire 8 seconds at which time the light came on simultaneously with the raising of the 2-way mirror screen; (3) light on for 4 seconds and then off for 4 seconds; (4) light off for 4 seconds then on for 4 seconds; (5) light on for 2 seconds, off for 4 seconds and on for 2 seconds; and, (6) light off for 2 seconds, on for 4 seconds and off for 2 seconds. A randomized 6 x 6 Latin Square was used to assign subject and condition per day. Testing was conducted six days per week which allowed each condition to be presented to each subject every week. The 6 x 6 Latin Square was then repeated five times for a total test period of 30 weeks or 180 days. The 30 weeks were divided into 3 blocks of 10 weeks each. The results were analyzed with the Sequential State Theory (SST) which was developed by King and Fobes and is a two-stage theory of learning. The two stages are defined as attention which is followed by an associative stage of bias free learning. The results indicated that, to the contrary of some recent research, proactive inhibition was a significant source of error under all conditions and for both species. There were no significant species differences as a function of the different lighting condition during the period of delay. The Sequential State Theory hypothesizes a triphasic model for the acquisition of a complex learning task. When the learning task is sufficiently difficult there are three clearly identifiable curves in the acquisition of learning. First, the animal exhibits error tendencies such as position perseveration. This tendency is followed by an increase in random responding. Finally, detect responses emerge which are manifested by attending to the relevant dimensions of the stimulus object. The data for both the capuchin monkeys and squirrel monkeys supported this model of learning with the response curves emerging in the predicted manner.

Spatial relationalleaming can be defined as the use of the spatial (geometric) relationship between two or more cues (landmarks) in order to locate additional points in space (O'Keefe and Nadel, 1979). An internal spatial representation enables an animal to compute novel locations and travel routes from familiar landmarks and routes (Dyer, 1993). A spatial representation is an internal construct mediating between perceived stimuli in the environment and the behaviour of the animal (Tolman, 1948). In this type of spatial representation the information encoded must be isomorphic with the physical environment such that the geometric relations of distance, angle and direction are maintained or can be computed from the stored information (Gallistel, 1990). A series of spatial and foraging task experiments were conducted to investigate the utilisation of spatial relational learning as a spatial strategy available to cotton-top tamarins (Sag uinus oedipus oedipus). The apparatus used was an 8x8 matrix of holes set in an upright wooden board to allow for the manipulation of visual cues and hidden food items such that the spatial configuration of cues and food could be transformed (translated or rotated) with respect to the perimeter of the board. The definitive test of spatial relational learning was whether the monkeys relied upon the spatial relationship between the visual cues to locate the position of the hidden food items. In a control experiment testing for differential use of perceptual information the results showed that if given the choice, tamarins relied on visual over olfactory cues in a foraging task. Callitrichids typically depend on olfactory communication in socio-sexual contexts so it was unusual that olfaction did not also play a significant role in foraging. In the first spatial learning experiment, the tamarins were found to rely on the three visually presented cues to locate the eleven hidden food items. However, their performance was not very accurate. In the next experiment the task was simplified so that the types of spatial strategies the monkeys were using to solve the foraging task could be clearly identified. In this experiment, only two visual cues were presented on either end of a line of four hidden food items. Once the monkeys were trained to these cues, the cues and food were translated and/or rotated on the board. Data from the beginning and middle of each testing session were used in the final analysis: in a previous analysis it was found that the monkeys initially searched the baited holes in the beginning of a testing session and thereafter predominantly searched unbaited holes. This suggests that they followed a win-stay/lose-shift foraging strategy, a finding that is supported by other studies of tamarins in captivity (Menzel and Juno, 1982) and the wild (Garber, 1989). The results also showed that the monkeys were searching predominately between the cues and not outside or around of them, indicating that they were locating the hidden food by using the spatial relationship between the visual cues. This provides evidence for the utilisation of spatial relational learning as a foraging strategy by cotton-top tamarins and the existence of complex internal spatial representations. Further studies are suggested to test captive monkeys' spatial relational capabilities and their foraging strategies. In addition, comparative and field studies are outlined that would provide information regarding New World monkeys' spatial learning abilities, neurophysiological organisation and the evolution of complex computational processes.

When different foraging specialists in a homospecific group have the option of joining each other's food discoveries, a skill pool may be established. Two field experiments on urban populations of feral pigeons (Columba livia) show that this species has the first prerequisite of the skill pool effect, the presence of individual foraging specialisations. Urban pigeons show marked individual variation in daily feeding site use patterns and food preferences. Two aviary experiments on a captive flock of C. livia show that pigeons also have the second prerequisite of skill pools, exchangeable producer-scrounger roles. Different individuals adopt producer or scrounger roles depending on patch type and flock composition when given four different food discovery tasks. Scrounging increases an individual's tendency to associate with producers, while simultaneously inhibiting observational learning of the food finding technique.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 41-45). Also available via the Internet.

Thesis (Ph. D.)--Michigan State University. Dept. of Psychology, 2006. / Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 175-190). Also issued in print.

Thesis (Ph. D.)--Duke University, 2007.

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Six squirrel monkeys were tested on short-term memory tasks assessing ability to suppress perseverative responses that had been previously reinforced. Each trial was divided into three parts: Initial Preference Assay (IPA), Bias-Conditioning (BC), and Reversal Conditioning (RC), and alternated between two conditions: experimental and control. Strength of response bias (based on choices of response during IPA) exceeded chance levels for each monkey. Eighty-four percent of responses to BC of the experimental trials were made to the response loci chosen in IPA even though that response was not rewarded. Monkeys made 38% correct responses during RC but shifted from making most errors during control trials in the beginning of the experiment to making most errors during experimental trials by the end of the experiment. Monkeys had developed a strategy of persevering from IPA to BC and then shifting to the other, not previously chosen window on RC, which led to correct responses in the experimental trials. (Abstract shortened with permission of author.)