Reflexivity without identity matching training: A first demonstration.

Until now, the equivalence property of reflexivity-matching physically identical stimuli to themselves after training on a set of arbitrary matching relations-has not been demonstrated in any animal, human or nonhuman. Previous reports of reflexivity have either implicitly or explicitly involved reinforced training on other identity matching relations. Here we demonstrate reflexivity without prior identity matching training.

Symmetry in the pigeon with sample and comparison stimuli in different locations. II.

Pigeons were trained on arbitrary (hue-form) and identity (hue-hue and form-form) successive matching with center-key samples and left-key comparisons. Later, they were tested on form-hue (symmetry) probe trials that were structured either in the different-locations fashion as the baseline trials (viz., center-key samples and left-key comparisons) or with a constant location by using center-key samples and center-key comparisons.

Functional relations and cognitive psychology: Lessons from human performance and animal research.

We consider requirements for effective interdisciplinary communication and explore alternative interpretations of "building bridges between functional and cognitive psychology." If the bridges are intended to connect radical behaviourism and cognitive psychology, or functional contextualism and cognitive psychology, the efforts are unlikely to be successful. But if the bridges are intended to connect functional relationships and cognitive theory, no construction is needed because the bridges already exist within cognitive psychology.

A successful search for symmetry (and other derived relations) in the conditional discriminations of pigeons.

Symmetry is one of three derived relations (along with transitivity and reflexivity) that indicate that explicitly trained conditional relations are equivalence relations and that the elements of those trained relations are members of a stimulus class. Although BA symmetry is typically observed after AB conditional discrimination training in humans, it has been an elusive phenomenon in other animals until just recently. This paper describes past unsuccessful attempts to observe symmetry in non-human animals and the likely reasons for that lack of success.

Transitive and anti-transitive emergent relations in pigeons: support for a theory of stimulus-class formation.

Stimulus class formation is inferred when conditional discrimination training yields new (emergent) conditional relations between the training stimuli. The present experiments demonstrated two such relations in pigeons after successive matching-to-sample training. Experiment 1 showed that transitivity (AC matching) emerged after training on AB and BC arbitrary matching plus BB identity matching: pigeons responded relatively more to the comparisons on AC test trials in which both the A samples and C comparisons were elements of reinforced arbitrary baseline relations involving the same nominal B stimulus.

Concurrent identity training is not necessary for associative symmetry in successive matching.

Pigeons demonstrate associative symmetry after successive matching training on one arbitrary and two identity relations (e.g., Urcuioli, 2008).

Associative concept learning in animals.

Nonhuman animals show evidence for three types of concept learning: perceptual or similarity-based in which objects/stimuli are categorized based on physical similarity; relational in which one object/stimulus is categorized relative to another (e.g., same/different); and associative in which arbitrary stimuli become interchangeable with one another by virtue of a common association with another stimulus, outcome, or response.

Symmetry in the pigeon with sample and comparison stimuli in different locations.

Pigeons typically do not show evidence for symmetry in two-alternative matching-to-sample but do demonstrate this emergent relation in successive (go/no-go) matching-to-sample. Because the sample and comparison stimuli are presented in the same spatial location (viz., on one key) during successive matching training and testing, this may be one reason why pigeons pass tests for symmetry in this paradigm.

Evidence for response membership in stimulus classes by pigeons.

Response membership in pigeons' stimulus-class formation was evaluated using associative symmetry and class expansion tests. In Experiment 1, pigeons learned hue-hue (AA) and form-form (BB) successive matching plus a modified hue-form (AB) task in which reinforcement was contingent upon a left versus right side-key response after the positive AB sequences. On subsequent BA (symmetry) probe trials, pigeons responded more often to the comparisons on the reverse of the positive than negative AB sequences and, more importantly, preferentially pecked the side key consistent with symmetry after the reversed positive sequences.

A replication and extension of the antisymmetry effect in pigeons.

Pigeons trained on successive AB symbolic matching show emergent BA antisymmetry if they are also trained on successive AA oddity and BB identity (Urcuioli, 2008, Experiment 4). In other words, when tested on BA probe trials following training, they respond more to the comparisons on the reverse of the nonreinforced AB baseline trials than on the reverse of the reinforced AB baseline trials (the opposite of an associative symmetry pattern). The present experiment replicated this finding.

Emergent identity matching after successive matching training. II: Reflexivity or transitivity.

Three experiments evaluated whether the apparent reflexivity effect reported by Sweeney and Urcuioli (2010) for pigeons might, in fact, be transitivity. In Experiment 1, pigeons learned symmetrically reinforced hue-form (A-B) and form-hue (B-A) successive matching. Those also trained on form-form (B-B) matching responded more to hue comparisons that matched their preceding samples on subsequent hue-hue (A-A) probe trials.

Emergent identity matching after successive matching training, I: reflexivity or generalized identity.

This research investigated the source of an ostensible reflexivity effect in pigeons reported by Sweeney and Urcuioli (2010). In Experiment 1, pigeons learned two symmetrically reinforced symbolic successive matching tasks (hue-form and form-hue) using red-green and triangle-horizontal line stimuli. They differed in their third concurrently trained baseline task: form-form matching with stimuli appearing in the symbolic tasks (triangle and horizontal) for one group versus hue-hue matching with stimuli not appearing in the symbolic tasks (blue and white) for the other.

Reflexivity in pigeons.

A recent theory of pigeons' equivalence-class formation (Urcuioli, 2008) predicts that reflexivity, an untrained ability to match a stimulus to itself, should be observed after training on two "mirror-image" symbolic successive matching tasks plus identity successive matching using some of the symbolic matching stimuli. One group of pigeons was trained in this fashion; a second group was trained similarly but with successive oddity (rather than identity). Subsequently, comparison-response rates on novel matching versus mismatching sequences with the remaining symbolic matching stimuli were measured on nonreinforced probe trials.

Associative symmetry in a spatial sample-response paradigm.

Symmetry has been difficult to observe in nonhumans mainly because they seem to perceive stimuli as a conjunction of visual, spatial, and temporal characteristics. When such characteristics are controlled, symmetry does emerge in nonhumans (cf. Frank and Wasserman, 2005; Urcuioli, 2008).

Associative symmetry and stimulus-class formation by pigeons: the role of non-reinforced baseline relations.

Two experiments tested the assumption of Urcuioli's (2008) theory of pigeons' equivalence-class formation that consistent non-reinforcement of certain stimulus combinations in successive matching juxtaposed with consistent reinforcement of other combinations generates stimulus classes containing the elements of the reinforced combinations. In Experiment 1, pigeons were concurrently trained on symbolic (AB) and two identity (AA and BB) successive tasks in which half of all identity trials ended in non-reinforcement but all AB trials were reinforced, contingent upon either responding or not responding to the comparisons. Subsequent symmetry (BA) probe trials showed evidence of symmetry in one of four pigeons.

Extensive training is insufficient to produce the work-ethic effect in pigeons.

Zentall and Singer (2007a) hypothesized that our failure to replicate the work-ethic effect in pigeons (Vasconcelos, Urcuioli, & Lionello-DeNolf, 2007) was due to insufficient overtraining following acquisition of the high- and low-effort discriminations. We tested this hypothesis using the original work-ethic procedure (Experiment 1) and one similar to that used with starlings (Experiment 2) by providing at least 60 overtraining sessions. Despite this extensive overtraining, neither experiment revealed a significant preference for stimuli obtained after high effort.

Associative symmetry, antisymmetry, and a theory of pigeons' equivalence-class formation.

Five experiments assessed associative symmetry in pigeons. In Experiments 1A, 1B and 2, pigeons learned two-alternative symbolic matching with identical sample- and comparison-response requirements and with matching stimuli appearing in all possible locations. Despite controlling for the nature of the functional stimuli and insuring all requisite discriminations, there was little or no evidence for symmetry.

On the origins of emergent differential sample behavior.

Two experiments evaluated the source(s) of emergent differential sample behavior in pigeons. Initially, pigeons learned two-sample, two-alternative symbolic matching in which different patterns of sample responding were required to produce the comparisons. Afterwards, two other samples nominally identical to the comparisons were added to the matching task.

The nature of the response in Simon discriminations by pigeons.

Spence (1952) postulated that under some conditions, responding in simple discriminations is controlled by compounds or patterns consisting of the nominal discriminative cue, plus its spatial position. Stimulus control by such compounds was said to develop when no single cue or element was systematically reinforced more than any other. This analysis has been applied to good effect in understanding some peculiar accuracy results obtained from pigeons performing Simon discrimination tasks.

Effects of within-class differences in sample responding on acquired sample equivalence.

Two experiments examined whether acquired sample equivalence in many-toone matching was affected by variation in sample-response requirements. In each experiment, pigeons responded on either identical or different response schedules to the sample stimuli that occasioned the same reinforced comparison choice (i.e.

Deprivation level and choice in pigeons: a test of within-trial contrast.

Within-trial contrast has been proposed as a mechanism underlying preferences for stimuli that follow relatively more aversive events over stimuli that follow less aversive events. In this study, we manipulated deprivation level to test within-trial contrast predictions. In Experiment 1, pigeons encountered two discriminative stimuli, one presented when they were deprived and the other when they were prefed.

Sample and comparison location as factors in matching acquisition, transfer, and acquired equivalence.

Pigeons learned symbolic matching with samples appearing equally often on left and right keys. For a location-relevant group, the reinforced comparison choice for each sample reversed across sample locations; for a location-irrelevant group, the reinforced choices were the same. Consistent with the hypothesis that samples at different locations are functionally different for pigeons, Experiment 1 showed that matching acquisition was comparable in these two groups.

Value transfer contributes to ambiguous-cue discrimination learning.

Pigeons learned two concurrent simultaneous discriminations in which the S- for one served as the S+ for the other. When all correct choices were reinforced, accuracy on the former (positive vs. ambiguous-cue or PA) discrimination was lower than on the latter (negative vs.

When is a failure to replicate not a type II error?

Zentall and Singer (2007) challenge our conclusion that the work-ethic effect reported by Clement, Feltus, Kaiser, and Zentall (2000) may have been a Type I error by arguing that (a) the effect has been extensively replicated and (b) the amount of overtraining our pigeons received may not have been sufficient to produce it. We believe that our conclusion is warranted because (a) the original effect has not been replicated despite multiple attempts to do so and (b) the statement that more extended overtraining may be needed itself suggests that the original effect is not reliable.