Judgements of items viewed less than 100 ms prior are predominantly supported by a sensory, or iconic, memory system. Iconic memory is of high-capacity, but is also volatile and limited in duration. Judgements after longer delays increasingly rely on a working memory system, which is lower in capacity and volatility than sensory memory, but is longer in duration. In four experiments, several factors (e.g., length of delay, number of items, time to view items, presence of a visual mask) were manipulated during a spatial change-detection task conducted with humans and pigeons. Both species were exposed to trials with an array of colored circles (2, 3, and 4 circles in Experiment 1 and 2a; 4, 6, and 8 circles in Experiment 2b) followed by a brief delay (0, 50, and 100 ms in Experiment la; 0, 100, and 1000 ms in Experiments lb and 2), and then were presented with a test display in which the position of one of the items had changed. Pigeons, like humans, were less accurate in selecting the changed item with more items in the display and after longer delays. Pigeons were equally accurate on trials with 0 and 100-ms delays, but worse on trials with a 1000-ms delay; whereas, humans were equally accurate on 100-ms and 1000-ms delays, but better on 0-ms delay trials. Accurate change detection was disrupted in both species when a visual mask was inserted between the sample and test display after a short (100 ms), but not a long (1000 ms) delay. The results support similarity between species in the functional relationships between delay and memory systems, despite time course differences related to sensory memory.

Human and non-human animals exhibit a variety of response strategies (e.g., place responding) when searching for a familiar place or evading predators. We still know little about the conditions that support the use of each strategy. We trained rats to locate a hidden food reward in a small-scale spatial search task. The complexity of the search task was manipulated by reducing the number of search locations (25, 4, and 2) within an open-field apparatus and by comparison to a path-based apparatus (plus-maze). After rats were trained to reliably locate the hidden food, each apparatus was shifted to gauge whether rats were searching at the location of the goal relative to extramaze cues (i.e., place responding), or searching in the direction of the goal relative to a combination of intramaze and extramaze cues (i.e.,directional responding). The results indicate that the open field supported place responding when more than two response locations were present, whereas, the four-arm plus-maze supported strong directional responding. These results extend prior research into the role of task demands on search strategy, as well as support the use of the four-choice open field as an analog to the Morris water task for future studies targeting the neural underpinnings of place responding.

The increasing demand for highly automated and flexible tasks capable of assessing visual learning and memory in nonhuman animals has led to the exciting development of a wide array of prefabricated touchscreen-equipped systems. However, the high cost of these prefabricated systems has led many researchers to develop or modify their own preexisting equipment. We developed a freely downloadable App, the Touchscreeen Behavioral Evaluation System (TBES) for use in conjunction with an iPad (Apple, Cupertino, California) as an alternative to prefabricated touchscreen systems. TBES allows for stimulus presentation and data collection on an iPad. The touchscreen technology offered by the iPad is attractive to researchers due to its affordability, reliability, and resistance to false inputs. We highlight these, as well as the feasibility and procedural flexibility of TBES, in an effort to promote our system as a competitive alternative to those currently available.

A spatial task was used to investigate if a stimulus could set the occasion for responding to a landmark. Pigeons were trained with a positive occasion setter (OS; a colored background display) signaling the contingency between a landmark (LM; visual patterned stimulus) and the location of a rewarded response. The two most common tests of an OS (transfer tests and post-training extinction of the OS) were then conducted. In Experiment 1, two occasion setting pairs were trained (+←XA/YB→+/A-/B-) with unique spatial relationships to a reinforced goal location. Transfer tests (XB- and YA-) revealed more responding to a landmark when paired with the same OS from training (e.g., XA) than on transfer tests, which was greater still than landmark-only trials (A-). Three pigeons demonstrated good spatial control of responding by the LM on transfer tests. In Experiment 2, the contingency and spatial relationship (e.g., left or right) between LM A and the goal were signaled by the OS (+←XA/YA→+/+←ZB/C→+/A-/B-). LM C was trained without an OS to assess the role of training history during transfer. Transfer tests again indicated an OS could facilitate responding and the LM controlled the location of responding. Training history affected spatial control, but not facilitation, by LM C. Lastly, post-training extinction of X had no effect on facilitation or spatial control during subsequent XA trials. These experiments are the first to evaluate conditional control of spatial information by landmarks using both of the standard tests for occasion setting.

During feature-positive operant discriminations, a conditional cue, X, signals whether responses made during a second stimulus, A, are reinforced. Few studies have examined how landmarks, which can be trained to control the spatial distribution of responses during search tasks, might operate under conditional control. We trained college students to search for a target hidden on a computer monitor. Participants learned that responses to a hidden target location signaled by a landmark (e.g., A) would be reinforced only if the landmark was preceded by a colored background display (e.g., X). In Experiment 1, participants received feature-positive training (+←YB/ XA→+/A−/B−) with the hidden target to the right of A and to left of B. Responding during nonreinforced transfer test trials (XB−/YA−) indicated conditional control by the colored background, and spatial accuracy indicated a greater weighting of spatial information provided by the landmark than by the conditional cue. In Experiments 2a and 2b, the location of the target relative to landmark A was conditional on the colored background (+←YA/ XA→+/ ZB→+/ +←C /A−/B−). At test, conditional control and a greater weighting for the landmark’s spatial information were again found, but we also report evidence for spatial interference by the conditional stimulus. Overall, we found that hierarchical accounts best explain the observed differences in response magnitude, whereas spatial accuracy was best explained via spatial learning models that emphasize the reliability, stability, and proximity of landmarks to a target.

One of the many effects predicted by the Rescorla-Wagner model is overexpectation (OX). The OX effect is the finding that following compound training with two asymptotic elements, X and A, animals emit less conditioned responding (CR, e.g., nose poking) during tests of X alone compared to animals that did not receive compound training. We investigated the OX effect in the context of reward timing by training rats to expect sucrose at different times during X and recording the CR throughout the duration of X. Experiment 1 examined the OX effect using a traditional delayed conditioning procedure. In Experiment 2, the period during which sucrose was expected occurred either early or late during X. Tests revealed that less CR occurred in the OX group around the period that sucrose was previously overexpected, and was otherwise similar in response functions to the control group that did not receive the compound manipulation. These are the first studies pitting the effects of OX with an animal's ability to time their expectation of food. (C) 2014 Elsevier Inc. All rights reserved.

Visual discrimination tasks are commonly used to assess visual learning and memory in non-human animals. The current experiments explored the suitability of an iPad (Apple, Cupertino, California), as a low-cost alternative touchscreen for visual discrimination tasks. In Experiment 1, rats were trained with patterned black-and-white stimuli in a successive non-match to sample procedure. Rats successfully interacted with the iPad but failed to learn to withhold responding on trials in which the sample matched the comparison. Experiment 2 used the same patterned stimuli, but the procedure was simplified to a successive discrimination procedure and we explored the use of procedures known to facilitate discrimination learning. Rats that received training with differential outcomes and a differential reinforcement of other behavior schedule successfully acquired the task. In Experiment 3, the same rats were tested in a simultaneous discrimination task and we explored the use of a correction and non-correction method during acquisition. Rats that failed to learn the discrimination in the previous experiment, improved while trained with the correction method. These experiments support the use of the iPad in visual discrimination tasks and inform future studies investigating learning and memory within a touchscreen-equipped (iPad or other) apparatus.