CAN IMITATION IN PIGEONS BE EXPLAINED BY LOCAL ENHANCEMENT TOGETHER WITH TRIAL-AND-ERROR LEARNING?

Abstract— Zentall Sultan and Sherburne (1996) reported that pigeons observing a conspecific demonstrator either step on or peck at a treadle to obtain food subsequently showed a significant tendency to manipulate the treadle as had their demonstrator. Zentall et al suggested this finding showed observer pigeons had learned by imitation to peck at or step on the treadle. However, the same result might have been obtained of pigeons had learned to step on the treadle by trial and error, and pigeons exposed to a treadle-pecking demonstrator had come to peck at the treadle as a result of nonimitative social learning processes such as local enhancement or contagion. Here we report the results for two control groups showing that pigeons do not learn to step on or peck at a treadle for food reward unless they observe a relevant demonstrator. These results considerably strengthen the original conclusion. Future research using the two action method to demonstrate imitative learning should include similar controls.     

Cholinergic receptor antagonists impair formation of intermediate-term memory in the chick

Several experiments examined the effects of cholinergic receptor antagonists on formation of memory in the chick. Scopolamine produced amnesia in chicks trained on a one-trial peck avoidance task in a dose-dependent manner. Pretraining injection of scopolamine produced amnesia that developed between 15 and 30 min after training, suggesting that scopolamine interferes with intermediate-term memory (ITM), previously described to be active during this time (Patterson, Alvarado, Warner, Bennett, & Rosenzweig, 1986). Pretraining injection of scopolamine or ouabain, an inhibitor of ATPase activity shown previously to inhibit formation of ITM, produced identical time courses of amnesia development, supporting the hypothesis that scopolamine interferes with ITM. Pirenzepine, an inhibitor of M1 muscarinic receptors, was effective in producing amnesia, whereas gallamine, an M2 receptor inhibitor, did not produce amnesia. These results suggest that M1, but not M2, receptors are involved in memory formation in the chick.     

The TMS 9918A VDP: A new device for generating moving displays on a microcomputer

A procedure for creating smooth and continuous moving displays on a microcomputer using the TMS 9918A video display processor (VDP) is discussed. This processor shares all of the features of other VDPs and, in addition, enables the user to directly program smooth motion of specified graphics shapes (sprites) with multilevel pattern overlaying. The general principles for programming this video chip are described, and a machine language driver is presented. Three illustrative applications from the event perception literature—wheel-generated motion, kinetic disruption of optical texture, and biomechanical motions—are presented as demonstrations of how the unique features of this video chip can be implemented in the creation of dynamic displays.     

Pattern-directed attention in uncertain-frequency detection

The role of early pattern components as cues in uncertain frequency detection was investigated in four probe-signal experiments. Listeners heard two consecutive presentations of one of two 12-tone patterns in a noise background. One presentation of the pattern was complete, whereas the other was missing the 11th (primary) tone. Listeners were required to indicate which presentation was complete. On 20% of the test trials, the 11th component of the complete pattern was replaced with one of four probe tones. The results indicated that listeners were more sensitive to the primary tone than to probe tones, and this selective sensitivity changed on a trial-by-trial basis as a function of the attentional cues provided by early pattern components. The data suggested two cue functions: (1) an “informational” function in providing information regarding which of two primary tones is likely to occur on a given trial, and (2) a “frequency” function that “automatically” directs listening to an appropriate frequency range and narrows or “fine tunes,” the listening band.     

Law,professional practice,and professional organizations: Where do we go from here?

The ethical dilemmas presented to the practicing school psychologist by the plethora of laws that dictate procedures, policies, and instrumentation are discussed. The function of professional organizations, both national and state, is described as (a) anticipating legislation, (b) developing political impact, (c) affecting existing laws, and (d) affecting proposed legislation. Coordination of efforts among various groups and development of political expertise is urged as a way to approach issues of concern to both psychologists and their clients.     

Assessing treatability in mentally disordered offenders: A conceptual and methodological note

The assessment of treatability in mentally disordered offenders has rarely been addressed through empirical research, despite its frequent use in clinical and legal decision-making. We describe four necessary steps for establishing the requisite research base for treatability evaluations: (a) criterion specification, (b) the development of reliable measures, (c) the validation of these measures with treatment outcome data, and (d) the incorporation of environmental and base rate information.     

Some effects of response-correlated increases in reinforcer magnitude on human behavior

After training under short or long fixed-interval schedules, humans responded under a modified fixed-interval schedule in which magnitude of reinforcement (X or 2X) was minimally correlated with response frequency. Response frequencies that equaled or exceeded a minimum response criterion were followed by the larger reinforcer at the end of the interval; otherwise, the smaller reinforcer was delivered. The modified schedule alternated with the baseline schedule across conditions. In a control condition, the reinforcer magnitudes produced by control subjects were yoked to those of experimental subjects. Experimental subjects, but not control subjects, showed increased responding. In addition to the baseline and modified fixed-interval schedules used in Experiment 1, subjects in Experiment 2 also responded under a second modified fixed-interval contingency in which increases in reinforcer magnitude were more highly correlated with response frequency. Experimental subjects, but not control subjects, showed increased responding under both procedures. Direct comparison of these two procedures showed that the high-correlation procedure produced greater increases in responding than did the low-correlation procedure.     

Human Performance Under Progressive Ratio Contingencies

The Psychological Record - Ten human subjects experienced a progressive ratio schedule under three different reinforcement conditions; (a) 20-point increments on a computer screen for each ratio...