Role of interference in retention by rats with hippocampal lesions.

Involvement of the hippocampus in memory was studied in the rat by employing a retention task with and without interpolated activity. Rats with extensive damage to hippocampus were able to relearn a preoperatively acquired single-alternation task with savings and to perform the single alternation with relatively long delays at a level similar to that of control subjects. However, hippocampals were more affected than normals by an interpolated activity that interferes with retention. The finding of normal retention combined with increased susceptibility to interference supports the view that the memory impairment in subjects with damage to hippocampus may be due to an excess of interference among stored information.     

A computer-controlled system for training and testing primates

The hardware and software for a computer-controlled training and testing system for primates are described. The computer (DDP-116 in the Computer-Controlled Psychology Laboratory at Carnegie-Mellon University) controls all stimulus presentation, reinforcement, and records data in a form ready for analysis on a larger computer.     

Strategy selection in a task with spatial and nonspatial components: effects of fimbria-fornix lesions in rats.

The main purpose of the present research was to investigate the ability of rats to learn a 12-arm radial maze task that requires the concurrent utilization of both spatial and intramaze cue information. The task involves in a single trial both place and cue learning as well as reference memory (RM) and working memory (WM). Since the animal can choose place and cue arms in any order, the strategies employed to learn the task can be studied as well as the kinds of memory errors that are made. The results of Experiment 1 showed that the number of errors made on the place and cue components of the task did not differ, and that more RM than WM errors were made early during learning. As the task was learned, the animals tended to choose the place arms before choosing the intramaze cue arms, thus suggesting that a spatial strategy was employed first followed by a cue strategy. In Experiment 2 lesions of the fimbria-fornix resulted in temporary impairments in both RM and WM that were especially apparent on the spatial component of the task. The lesioned rats also switched from choosing mostly place arms early during the trial to choosing more cue arms. While fimbria-fornix lesioned rats recovered from the memory impairments with training, the change in response strategy persisted throughout postoperative testing. The procedure of combining both spatial and non-spatial components concurrently in the same task should prove of value in studying response strategies in animals.     

The effects of selective ibotenate lesions of the hippocampus on conditioned inhibition and extinction

Previously, Solomon (1977) reported that aspiration lesions of the dorsal hippocampus in rabbits had no effect either on the acquisition of Pavlovian conditioned inhibition or on performance during a subsequent retardation test. The present experiment confirmed and extended these findings by showing that rats with ibotenate lesions of the complete hippocampus (the dorsal and ventral hippocampus and the dentate gyrus) were also unimpaired on the same types of tasks. Additional tests with the same rats showed that removing the hippocampus significantly impaired extinction of responding to a stimulus that had been previously trained with an appetitive unconditioned stimulus. The performance of the lesioned rats on a summation test was also marginally, but not significantly, different from that of controls. The data are discussed with reference to the idea that the hippocampus is involved with the formation of some, but not all, types of inhibitory associations.     

Massed versus distributed exposure and imaging of faces: Changing the test view

This research examined the effects of massed versus distributed exposure and imaging of faces, and the effects of changing the study-to-test view on subsequent recognition performance. The massed procedure consisted of individual faces exposed once for 6 s, followed by a 30 s off period. The distributed procedure consisted of faces exposed three times for 2 s, followed by a 10 s off period after each exposure. During the off periods, groups of participants either imaged the previous face, imaged another face, or performed an irrelevant letter-search task. Results showed that distributed exposure and post-exposure imaging of target faces facilitated recognition, but these effects primarily occurred when the same facial view was given at both study and test. Recognition diminished when the target was presented in a different view at test, but when combined with distributed presentation and target imaging, performance was enhanced. Implications for suspect identification and recognition of other kinds of complex visual stimuli are discussed.     

Culture in the context of intercultural negotiation.

This study explores culture's effect on behaviors and outcomes in intercultural negotiation and examines how those effects are moderated by role. Eighty U.S. and international students took part in a previously developed negotiation task (Pruitt, 1981) and completed Hui and Triandis's (1986) individualism‐collectivism (INDCOL) scale. Negotiation interactions were coded for information sharing, offers, and distributive tactics. Findings show that a negotiation dyad's collectivism is positively associated with higher joint profit. The effects of culture on both communication behaviors and joint outcomes, however, differ by role of the negotiator. In particular, seller collectivism has larger and more consistent effects on communication behavior and joint profit than buyer collectivism. Results support a ‘culture in context’ perspective of negotiation that takes into account negotiator qualities, contextual and structural features of the negotiation, and mediating processes in addition to cultural values.