Observing responses in rats: Support for the secondary reinforcement hypothesis

Rats' lever presses on a retractable lever earned brief presentations of discriminative stimuli signalling periods in which responding on an alternative lever was either non-reinforced (extinction) or reinforced on a random ratio schedule. The predictions of two theoretical accounts of this behaviour were tested by studying the effects of omitting either the stimulus signalling the reinforced or that signalling the non-reinforced schedule component. Under these conditions rats' behaviour is determined by the conditioned, affective properties of the stimuli rather than by their purely informational properties.     

Echoic memory processes in good and poor readers

Four experiments were conducted to determine whether echoic memory plays a role in differences between good and poor readers. The first two experiments used a suffix procedure in which the subject is read a list of digits with either a tone control or the word go appended to the list. For lists that exceeded the length of the subjects memory span by one digit (i.e., that avoided ceiling effects), the poor readers showed a larger decrement in the suffix condition than did the good readers. The third experiment was directed at the question of whether the duration of echoic memory is different for good and poor readers. Children shadowed words presented to one ear at a rate determined to give 75-85% shadowing accuracy. The items presented to the nonattended ear were words and an occasional digit. At various intervals after the presentation of the digit, a light signaled that the subject was to cease shadowing and attempt to recall any digit that had occurred in the nonattended ear recently. Whereas good and poor readers recalled the digit equally if tested immediately after presentation, the poor readers showed a faster decline in recall of the digit as retention interval increased. A fourth experiment was conducted to determine whether the differences in echoic memory were specific to speech stimuli or occurred at a more basic level of aural persistence. Bursts of white noise were separated by 9-400 ms of silence and the subject was to say whether there were one or two sounds presented. There were no differences in detectability functions for good and poor readers.     

The Effect of Erroneous Knowledge of Results on Skill Acquisition when Augmented Information is Redundant

Even though it can be shown that verbal knowledge of results (KR) is redundant with sensory feedback for learning certain motor skills, such findings do not eliminate the possibility that when KR is available it influences underlying learning processes. In order to examine the function of KR more closely, two experiments were designed in which the subjects received conflicting information about their own sensory feedback and the KR presented by the experimenter. In Experiment 1, two erroneous-KR groups, a correct-KR group, and a no-KR group performed 150 practice trials on a simple anticipation timing task and then performed three no-KR retention tests of 30 trials each following intervals of 10 minutes, 1 week, and 1 month. The results supported previous findings that providing correct KR is redundant in anticipation tasks. However, learning was influenced by KR as subjects performed according to the erroneous KR information, thereby ignoring their sensory feedback even after a 1-month interval. In Experiment 2, subjects practised a more complex striking response for the anticipation task for 75 trials and then performed no-KR retention trials either immediately, or 1 day or 1 week later. One of the groups received erroneous KR after 50 practice trials with correct KR. The results confirmed and extended those from Experiment 1, as erroneous KR, even after initial practice with correct KR, influenced retention performance. These results indicate that although KR provides information that is not needed to learn anticipation timing skills, this augmented verbal information is a dominant source of information that influences underlying cognitive processes involved in learning motor skills.