Reduced Frequency of Knowledge of Results Enhances Acquisition of Skills in Rats as in Humans.

Macphail's (1985) null hypothesis challenged researchers to demonstrate any differences in intelligence between vertebrate species. Rather than focus on differences, we asked whether rats would show the same unexpected, counterintuitive features of skill learning observed in humans: Factors that degrade performance during acquisition often enhance performance in a subsequent retention/autonomy phase. Providing post-trial "knowledge of results" (KR) on 30-67% of trials instead of 100% degrades accuracy, yet increases retention in a subsequent phase without KR. We tested this feature by providing three groups of rats with KR on every trial (100% KR), 67% KR, or 0% KR. We also provided operant feedback in every trial for completing the left-right lever-press skill (food for correct sequences, timeout for all others). In the autonomy phase, we assessed their ability to complete the skill independently-in the absence of differential cues and KR feedback. In agreement with human performance in the autonomy phase, 67% KR yielded higher skill accuracy than providing 100% KR. Also, providing 67% KR improved skill accuracy above that observed with operant feedback alone (0% KR). Rather than degrading performance during acquisition, the 67% KR condition yielded unexpected higher accuracy than the other conditions. Accuracy increased systematically across our extended acquisition phase, which provided each rat with over 3600 trials compared to 20-30 trials for human studies. Providing limited KR promoted skill learning in rats as it does in humans, consistent with the conjecture that both species share common learning processes. Introducing difficulties to rats during training improved their autonomy.

Assessment of progressively delayed prompts on guided skill learning in rats.

We examined the controlling factors that allow a prompted skill to become autonomous in a discrete-trials implementation of Touchette's (1971) progressively delayed prompting procedure, but our subjects were rats rather than children with disabilities. Our prompted skill was a left-right lever-press sequence guided by two panel lights. We manipulated (a) the effectiveness of the guiding lights prompt and (b) the presence or absence of a progressively delayed prompt in four groups of rats. The less effective prompt yielded greater autonomy than the more effective prompt. The ability of the progressively delayed prompt procedure to produce behavioral autonomy depended upon characteristics of the obtained delay (trial duration) rather than on the pending prompt. Sequence accuracy was reliably higher in unprompted trials than in prompted trials, and this difference was maintained in the 2 groups that received no prompts but yielded equivalent trial durations. Overall sequence accuracy decreased systematically as trial duration increased. Shorter trials and their greater accuracy were correlated with higher overall reinforcement rates for faster responding. Waiting for delayed prompts (even if no actual prompt was provided) was associated with lower overall reinforcement rate by decreasing accuracy and by lengthening trials. These findings extend results from previous studies regarding the controlling factors in delayed prompting procedures applied to children with disabilities.

On the dynamics of stimulus control during guided skill learning in nonhumans.

This study measured skill acquisition in the presence and absence of guiding cues in pigeons. It asked whether the speed of development of autonomy for the motor skill is influenced by the difficulty level of two guiding-cue conditions requiring the same left-right response sequence. The Follow-Red condition required a simple go, no-go discrimination (red=S+, green=S-), whereas the Red-Green condition was a more difficult simultaneous chain requiring sensitivity to the serial order of key colors (red=S+, green=S- for the first peck, but red=S-, green=S+ for the second peck). Pigeons exposed to the difficult Red-Green condition displayed significantly higher accuracy levels during no-cues conditions earlier in training than those exposed to the easier Follow-Red condition. A modified Power Law of Practice was used to evaluate the null hypothesis that autonomy develops equally in explicit guiding-cues conditions and no-cues conditions. This hypothesis was retained in the Follow-Red condition but rejected in the Red-Green condition. Practice completing the response sequence in the Follow-Red and no-cues conditions both contributed equally to autonomy. Autonomy developed faster in the Red-Green group in both conditions, and it developed unexpectedly rapidly during the second guiding-cues condition, implying the involvement of a second process for the Red-Green condition. We discuss the implications of these results to prompt dependence in children with learning disabilities, the transfer of stimulus control, and potential behavioral interventions.

The influences of guiding cues on motor skill autonomy in rats.

How does the effectiveness of guiding cues influence the development of motor skill autonomy? We utilized two sets of guiding cues (lights vs. reversed-lights conditions) that differed in their effectiveness to control a left-right leverpress sequence in rats. We separately measured the development of stimulus control by panel lights on guiding-cues trials and the development of stimulus control by practice cues on no-cue probe trials within the same sessions. Accuracy in the presence of the guiding cues was acquired faster in the lights condition than in the reversed-lights condition, but subjects in the reversed-lights condition were more able to complete the skill autonomously than those in the lights condition. Throughout acquisition, control by guiding cues and practice cues developed at the same rate in the reversed-lights condition, but control by practice cues (autonomy) developed at a slower rate than did control by guiding cues in the lights condition. At the end of training, subjects that had been exposed to the reversed-lights condition displayed higher levels of autonomy than did those exposed to the lights condition. The less effective guiding cue (reversed-lights) produced greater levels of autonomy than did the more effective cue (lights), even though control by this guiding cue developed more slowly. Thus, guiding your child by the hand too much may reduce his or her ability to complete the task independently. We discuss the similarity to prompt dependence in children with learning disabilities and transfer of stimulus control.

Why don't guiding cues always guide in behavior chains?

This research focused on the changes in stimulus control that influence an animal's ability to master a behavioral skill. We assessed stimulus control by (a) predictive environmental cues (panel lights) and (b) practice cues resulting from the subject's own behavior, as rats learned to complete a left-right lever-press sequence. Following a demonstration of overshadowing by Reid, Nill, and Getz (Behavioural Processes 84: 511-515, 2010), in which stimulus control by the panel lights overshadowed control by practice cues, four additional experiments replicated and assessed this overshadowing effect. In Experiment 1, we discovered a powerful asymmetry: Rats failed to adapt to a lights → reversed-lights transition, but adapted immediately to a reversed-lights → lights transition. Experiment 2 was designed to measure the interactions between these stimulus conditions and practice cues. In Experiment 3, we measured the effect of these stimulus conditions on acquisition rates. Finally, in Experiment 4 an ABA design was used to assess the effects of prior exposure to condition A on B → A transitions, and we found that prior exposure generally reversed the effects observed in B → A transitions presented first or in isolation. We discuss feature-positive bias and spatial S-R compatibility as potential explanations of the observed insensitivity to cues that should be, at face value, highly predictive of food during the acquisition of a behavioral skill. Perfectly predictive cues in behavior chains do not always guide behavior.

Border collie comprehends object names as verbal referents.

Four experiments investigated the ability of a border collie (Chaser) to acquire receptive language skills. Experiment 1 demonstrated that Chaser learned and retained, over a 3-year period of intensive training, the proper-noun names of 1022 objects. Experiment 2 presented random pair-wise combinations of three commands and three names, and demonstrated that she understood the separate meanings of proper-noun names and commands. Chaser understood that names refer to objects, independent of the behavior directed toward those objects. Experiment 3 demonstrated Chaser's ability to learn three common nouns--words that represent categories. Chaser demonstrated one-to-many (common noun) and many-to-one (multiple-name) name-object mappings. Experiment 4 demonstrated Chaser's ability to learn words by inferential reasoning by exclusion--inferring the name of an object based on its novelty among familiar objects that already had names. Together, these studies indicate that Chaser acquired referential understanding of nouns, an ability normally attributed to children, which included: (a) awareness that words may refer to objects, (b) awareness of verbal cues that map words upon the object referent, and (c) awareness that names may refer to unique objects or categories of objects, independent of the behaviors directed toward those objects.

Changes in stimulus control during guided skill learning in rats.

We examined the changes in stimulus control occurring during guided skill learning in rats. Twenty rats were trained to complete a left-right sequence of lever presses guided by the onset and offset of panel lights over their respective levers. Once sequence accuracy was high and stable, the rats were divided into two groups. For the No-Lights group, the lights were eliminated without changing the response requirements. Sequence accuracy decreased in all subjects, but accuracy was higher than that predicted by random chance. More practice produced greater autonomy and reduced dependence on the guiding lights. For the Reversed-Lights group, the lights were presented in reversed order without changing the response requirements. Sequence accuracy immediately plummeted and did not recover, violating expectations of automatization. The guiding lights appeared to overshadow other sources of stimulus control.

Resistance to change within heterogeneous response sequences.

Three experiments investigated how instrumental and Pavlovian contingencies contribute to resistance to change (RTC) in different ordinal response positions within heterogeneous response sequences in pigeons. RTC in the initial and terminal response positions of a three-response sequence were compared in Experiment 1, which presented three colored key lights in succession in each trial; and in Experiment 2, which severely degraded Pavlovian contingencies by presenting the lights simultaneously at each ordinal position. Experiment 3 eliminated the instrumental contingency in a high-order sign-tracking procedure. When the instrumental contingency was in effect, RTC of the initial position was greater than the terminal position (Initial RTC > Terminal RTC) when the Pavlovian contingencies were strong and when they were degraded. When the instrumental contingency was eliminated, RTC patterns reversed, producing a graded pattern of RTC (Initial < Middle < Terminal). Current theoretical approaches (e.g., behavioral momentum theory, conditioned reinforcement, and motivational control of instrumental conditioning) cannot account for these results. An alternative approach (a gradient model) shows that obtained measures of RTC in heterogeneous sequences may reflect a combination of three dissociable processes.

Resurgence of integrated behavioral units.

Two experiments with rats examined the dynamics of well-learned response sequences when reinforcement contingencies were changed. Both experiments contained four phases, each of which reinforced a 2-response sequence of lever presses until responding was stable. The contingencies then were shifted to a new reinforced sequence until responding was again stable. Extinction-induced resurgence of previously reinforced, and then extinguished, heterogeneous response sequences was observed in all subjects in both experiments. These sequences were demonstrated to be integrated behavioral units, controlled by processes acting at the level of the entire sequence. Response-level processes were also simultaneously operative. Errors in sequence production were strongly influenced by the terminal, not the initial, response in the currently reinforced sequence, but not by the previously reinforced sequence. These studies demonstrate that sequence-level and response-level processes can operate simultaneously in integrated behavioral units. Resurgence and the development of integrated behavioral units may be dissociated; thus the observation of one does not necessarily imply the other.

Route finding by rats in an open arena.

Rats were repeatedly exposed to an open arena containing two depletable food sources in a discrete-trials procedure. Their movement patterns were recorded and compared to adaptive foraging tactics such as minimizing distance or energy expenditure, thigmotaxis, and trail following. They were also compared to the predictions of the associative route-finder model of Reid and Staddon [Reid, A.K., Staddon, J.E.R., 1998. A dynamic route finder for the cognitive map. Psychol. Rev. 105 (3), 585-601]. We manipulated the presence/absence of food, goal cups, and a wooden runway to determine the influence of local and distal stimuli (visual, olfactory, and tactile) on movement patterns. Increased experience in the arena produced decreases in travel distance and time to the food sources. Local and distal stimuli influenced movement patterns in ways compatible with visual beacons and trail following. The route-finder model accurately predicted movement patterns except those that were influenced by local and distal stimuli. These results show how certain stimuli influence movement and provide a guide for the incorporation of local and distal stimuli in a future version of the dynamic route-finder model.