Independence of terminal-link entry rate and immediacy in concurrent chains

In Phase 1, 4 pigeons were trained on a three-component multiple concurrent-chains procedure in which components differed only in terms of relative terminal-link entry rate. The terminal links were variable-interval schedules and were varied across four conditions to produce immediacy ratios of 4:1, 1:4, 2:1, and 1:2. Relative terminal-link entry rate and relative immediacy had additive and independent effects on initial-link response allocation, and the data were well-described by a generalized-matching model. Regression analyses showed that allowing sensitivity to immediacy to vary across components produced only trivial increases in variance accounted for. Phase 2 used a three-component concurrent-schedules procedure in which the schedules were the same as the initial links of Phase 1. Across two conditions, the relative reinforcer magnitude was varied. Sensitivity to relative reinforcer rate was independent of relative magnitude, confirming results of prior studies. Sensitivity to relative reinforcer rate in Phase 2 did not vary systematically across subjects compared to sensitivity to relative entry rate in Phase 1, and regression analyses confirmed again that only small increases in variance accounted for were obtained when sensitivities were estimated independently compared with a single estimate for both phases. Overall, the data suggest that conditioned and primary reinforcers have functionally equivalent effects on choice and support the independence of relative terminal-link entry rate and immediacy as determiners of response allocation. These results are consistent with current models for concurrent chains, including Grace's (1994) contextual choice model and Mazur's (2001) hyperbolic value-added model.     

Paws + cause = pause? Memory load and memory blends in homophone recognition

Previous research has shown that separate information sources, activated closely together in time, can induce errors suggestive of memory blends. In Experiment 1, homophones were used to induce such memory errors. In a study task, participants made relatedness judgments to word pairs that included homophones (e.g., PAWS-BEAR). During this task, one group (study-similar) maintained memory loads with words that were orthographically similar to the presented homophones (e.g., JAWS). Another group (test-similar) maintained memory loads similar to those obtained for the study homophone's alternate spelling (e.g., CAUSE). A third group maintained no memory load during the task. In a surprise recognition test, participants were presented both previously viewed homophones (PAWS) and non-presented alternate spellings (PAUSE). We hypothesized that partially activated alternate spellings, in conjunction with the orthographically similar memory words, would result in the creation of blended memories. The results followed suit: The test-similar condition produced significantly elevated false alarms, relative to both the study-similar and the no-load conditions. Experiment 2 replicated these results while including memory loads to control for potential orthographic confusions. The findings are discussed in terms of multiple, episodic memories later activated as single, blended memories.     

Galantamine facilitates acquisition of hippocampus-dependent trace eyeblink conditioning in aged rabbits

Cholinergic systems are critical to the neural mechanisms mediating learning. Reduced nicotinic cholinergic receptor (nAChR) binding is a hallmark of normal aging. These reductions are markedly more severe in some dementias, such as Alzheimer's disease. Pharmacological central nervous system therapies are a means to ameliorate the cognitive deficits associated with normal aging and aging-related dementias. Trace eyeblink conditioning (EBC), a hippocampus- and forebrain-dependent learning paradigm, is impaired in both aged rabbits and aged humans, attributable in part to cholinergic dysfunction. In the present study, we examined the effects of galantamine (3 mg/kg), a cholinesterase inhibitor and nAChR allosteric potentiating ligand, on the acquisition of trace EBC in aged (30–33 months) and young (2–3 months) female rabbits. Trace EBC involves the association of a conditioned stimulus (CS) with an unconditioned stimulus (US), separated by a stimulus-free trace interval. Repeated CS–US pairings results in the development of the conditioned eyeblink response (CR) prior to US onset. Aged rabbits receiving daily injections of galantamine (Aged/Gal) exhibited significant improvements compared with age-matched controls in trials to eight CRs in 10 trial block criterion (P = 0.0402) as well as performance across 20 d of training [F(1,21) = 5.114, P = 0.0345]. Mean onset and peak latency of CRs exhibited by Aged/Gal rabbits also differed significantly [F(1,21) = 6.120/6.582, P = 0.0220/0.0180, respectively] compared with age-matched controls, resembling more closely CR timing of young drug and control rabbits. Galantamine did not improve acquisition rates in young rabbits compared with age-matched controls. These data indicate that by enhancing nicotinic and muscarinic transmission, galantamine is effective in offsetting the learning deficits associated with decreased cholinergic transmission in the aging brain.     

Birds of a feather and birds flocking together: physical versus behavioral cues may lead to trait- versus goal-based group perception

Entitativity perception refers to the perception of a collection of individuals as a group. The authors propose 2 perceptual-inferential bases of entitativity perception. First, perceivers would expect a collection of individuals with similar physical traits to possess common psychological traits. Second, perceivers watching a group of individuals engage in concerted behavior would infer that these individuals have common goals. Thus, both similarity in physical traits (e.g., same skin color) and concerted collective behavior (e.g., same movement) would evoke perception of group entitativity. Results from 5 experiments show that same group movement invariably leads to common goal inferences, increased perceived cohesiveness, and increased perceived entitativity. Moreover, same skin color evokes inferences of group traits and increases perceived homogeneity and perceived entitativity but only when skin color is diagnostic of group membership.     

Preference and resistance to change with constant- and variable-duration terminal links: independence of reinforcement rate and magnitude

Pigeons responded in a three-component multiple concurrent-chains procedure in which the variable-interval reinforcement schedules were the same across components but magnitudes differed across components. The terminal links were arranged either as a variable delay followed by presentation of a reinforcer ("variable duration") or as a fixed period of access to the schedule during which a variable number of reinforcers could be earned ("constant duration"). Relative reinforcement rate was varied parametrically across both types of conditions. After baseline training in each condition, resistance to change of terminal-link responding was assessed by delivering food during the initial links according to a variable-time schedule. Both preference and resistance to change were more sensitive to reinforcement-rate differences in the constant-duration conditions. Sensitivities of preference and resistance to change to relative reinforcement rate did not change depending on relative reinforcement magnitude. Taken together, these results confirm and extend those of prior studies, and suggest that reinforcement rate and magnitude combine additively to determine preference and resistance to change. A single structural relation linking preference and resistance to change describes all the data from this and several related studies.     

The relative influence of attitudes and subjective norms from childhood to adolescence: between-participant and within-participant analyses

Children and adolescents (ages 8-16) were asked to indicate their behavioral intentions, attitudes, and subjective norms for 34 behaviors. Between-participant and within-participant analyses demonstrated that attitudes and subjective norms were good predictors of behavioral intentions both singly and in combination. In addition, attitudes generally were better predictors than were subjective norms both across behaviors and across participants. Most importantly, however, there were no differences in the relative importance of attitudes and subjective norms in predicting behavioral intentions across age groups.     

Anxiety and outcome predictions

Research shows that people display a downward shift in their predictions in anticipation of performance and feedback. The authors used a misattribution paradigm to explore whether anxiety serves as a signal for predictions. Participants (N = 108) anticipating results from an important test either immediately or in a few days were or were not encouraged to attribute any arousal they experienced to coffee they consumed earlier. Consistent with predictions, participants encouraged to attribute their arousal to the coffee were optimistic in their predictions even when anticipating immediate test feedback. In addition, the more participants attributed their arousal to the coffee, the more optimistic they were in their predictions. Ancillary analyses suggest that anxiety can be a cause rather than a consequence of less optimistic predictions.     

Rapid acquisition of preference in concurrent chains

We report two experiments using a concurrent-chains procedure in which one terminal-link schedule was fixed-interval 8 s and the alternative schedule changed randomly from day to day. In Experiment 1, the alternative schedule varied between 4 s and 16 s according to a pseudorandom binary sequence similar to the one used by Hunter and Davison (1985). Similar to results with concurrent schedules, pigeons' response allocation in the initial link was most sensitive to the schedules arranged in the current session, although some effect of prior history was evident. Overall sensitivity was lower than for comparable data from steady-state research. In Experiment 2, a unique value between 2 s and 32 s was used for the alternative-schedule delay in each session. Sensitivity levels were similar to Experiment 1 and remained unchanged across 61 sessions of training. For all subjects, sensitivity was greater when the alternative-schedule delay was greater than 8 s compared with when it was less than 8 s. Generalized-matching plots revealed evidence of clustering of data points into two groups for some pigeons, suggesting that a process similar to a categorical discrimination may have at least partly determined response allocation. Overall, this research shows that pigeons' initial-link response allocation can adjust rapidly to frequent changes in the terminal links.     

Models of causation and the semantics of causal verbs

This research examines the relationship between the concept of CAUSE as it is characterized in psychological models of causation and the meaning of causal verbs, such as the verb cause itself. According to focal set models of causation (; ), the concept of CAUSE should be more similar to the concepts of ENABLE and PREVENT than either is to each other. According to a model based on theory of force dynamics, the force dynamic model, the concepts of CAUSE, ENABLE, and PREVENT should be roughly equally similar to one another. The relationship between these predictions and the meaning of causal verbs was examined by having participants sort causal verbs and rate them with respect to the dimensions specified by the two models. The results from five experiments indicated that the force dynamic model provides a better account of the meaning of causal verbs than do focal set models of causation. Implications for causal inference and induction are discussed.