The influence of landmark stability on control by occasion setters.

In an operant serial feature-positive procedure, an occasion setter (OSX) signals that a response will be reinforced in the presence of a second stimulus (e.g., a discriminative stimulus, A). During a transfer test, the OS is paired with a different discriminative stimulus. Experiment 1a tested transfer effects in a touchscreen-based spatial occasion setting task with pigeons. During training, four OSs (OSW, OSX, OSY, and OSZ) were paired on separate trials with landmark A (LMA) or B (LMB) and the opportunity for a reinforced response at one location to the immediate left (R1) or right (R2) of the LM (OSW→LMA:R1, OSX→LMA:R2, OSY→LMB:R1, OSZ→LMB:R2). Training also included non-reinforced trials of LMA and LMB alone (LMA- and LMB-) and trials of a non-modulated LM with R1 and R2 reinforced across separate trials (LMC:R1 and LMC:R2). After training, the number and spatial location of responses during test trials of a LM paired with the same OS as in training did not differ reliably from transfer tests of an OS paired with a different, modulated LM (OSW→LMB and OSY→LMA), but did differ from transfer to the non-modulated LM (OSX→LMC). Experiment 1b utilized the same pigeons and training with LMB to test the degree to which the spatial stability of a LM influenced transfer. Retraining with LMA was intended to establish it as a non-modulated, stable LM (LMA:R2). Subsequent tests with LMA revealed reduced modulation by the formerly trained OS (OSW), and complete disruption of modulation of spatial location during transfer with a different OS (OSY). These findings further our understanding of the conditions under which OSs may develop and transfer modulation.

Occasion setting during a spatial-search task with pigeons.

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.

Blocking between landmarks during 2-D (touchscreen) and 3-D (ARENA) search tasks with pigeons.

Many studies investigating cue competition have focused on the blocking effect. We investigated the blocking effect with pigeons using a landmark-based spatial search task in both a touchscreen preparation (Exp. 1a) and an automated remote environmental navigation apparatus (Exp. 1b). In Phase 1, two landmarks (LMs: A and Z) appeared on separate trials as colored circles among a row of eight (touchscreen) or six (ARENA) identical response units. Subjects were rewarded for pecking at a target response unit to the right of LM A and to the left of an extraneous LM, Z. During the blocking trials in Phase 2, LM X was presented in compound with a second LM (A) that had been previously trained. On control trials, LM Y was presented in compound with LM B and a target in the same manner as in the trials of AX, except that neither landmark had previously been trained with the target. All subjects were then tested with separate trials of A, X, B, and Y. Testing revealed poor spatial control by X relative to A and Y. We report the first evidence for a spatial-blocking effect in pigeons and additional support for associative effects (e.g., blocking) occurring under similar conditions (e.g., training sessions, spatial relationships, etc.) in 3-D and 2-D search tasks.

Feature-positive discriminations during a spatial-search task with humans.

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.

Task complexity modifies the search strategy of rats.

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.

Need to train your rat? There is an App for that: a touchscreen behavioral evaluation system.

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.

Visual discrimination learning with an iPad-equipped apparatus.

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.