THE PRESENT PAPER REPORTS two experiments on the influence of knowledge of results (KR) on the retention of simple motor skills. The evidence obtained has led to the generalization that conditions of training which enhance or detract from the perception of cues inherent in the task itself have a direct effect on the retention of motor skills. This view is compared to those of Miller (1953), Annett (1959, and Annett and Kay (1957), and discussed in relation to three major procedural variables: timing, scheduling, and accuracy or specificity of KR. More specifically the following questions will be discussed. Why does concurrent and more specific feedback always favour acquisition while hindering retention (Annett, 1959; Karlin, I960)? What effect does delay of KR have on retention? EXPERIMENT I defence Research Medical Laboratories Project no. 241, DRML Report no. 241-6, PCC no. D77-94-01-16, H.R. no. 224. 2 This paper is based upon the experimental portion of a doctoral dissertation submitted to l'lnstitut de Psychologie, University de Montreal, 1961. The author 'wishes to express his appreciation to Dr. David Be'Ianger for his guidance and cnticisin.

If rats are exposed successively to white noise, then to recorded rat squeals, or alternatively to squeals first and then white noise, and if, in both situations, they are allowed to shut off the auditory stimulation by applying pressure on a bar, they will touch the bar more frequently when exposed to white noise. The results indicate that the bar-pressing behavior is the expression of increased activity resulting from the increased stimulation.

I. Bilodeau (1956) studied the effect of delay of knowledge of results ( K R ) in a siruation in which additional responses were required during the delay, e.g., in the 2-trial delay condition KR on the first trial was given after the third trial had been completed, KR on the second trial after the fourth, etc.She found that with I-, 2-, 3-, or 5-trial delays rate of learning and level of accuracy reached within 30 KR trials decrease with the number of trials by which KR is delayed. .One purpose of the present experiment was to determine whether these findings hold for other simple skills. Confirmation of the Bilodeau finding would have special interest since the only other Es (Lorge & Thorndike, 1935) to use such a delay technique failed to find any learning, although only one trial intervened. A second purpose was to investigate the effect of the trial-delay method on the retention of such skills. A previous study (Lavery, 1962) suggested that any method which enhances the cues inherent in the [ask produces higher retention than one chat does not. It could be supposed that the trial-delay method obliges Ss to compare responses just made with responses made some trials back and thus they have more opportunity of profiting from such cues. It was predicted, therefore, that Ss trained with delay of KR would retain a skill better than Ss who received immediate KR.Two experiments were carried out. The first dealt with the problem of extending the trial-delay technique to orher tasks and of measuring its effecc on retention. The second experiment was designed to measure the effect upon retention of longer and shorter training periods within each technique. Subjects and A ppmatasTwenty-fou paid housewives (aged 25 to 36 yr.) served as Ss. Three tasks were used in order to have a within-subjects comparison of the three delay conditions.Manual lever.-This is a close duplicate of the apparatus used by Bilodeau and described in detail in Bilodeau and Ferguson ( 1953). Procedure used with this apparatus was as described in Bilodeau (1956). Briefly, the apparatus consists of a pulley and weight system at one end of a 2-ft. shaft and a lever at the other. The lever has an adjustable handle which was set at 14 in. from he '

AN EARLIER PAPER by the present authors (Lavery & Suddon, 1962) indicated that retention of a simple motor skill was directly related to the amount of training if knowledge of results (KR) during training was delayed by five intervening trials. On the other hand, when 0-trial delay KR was used in training, all groups, regardless of the amount of training given, exhibited the same level of retention, a finding previously reported by Baker and Young (1960). The influence of mode of KR upon the relation between amount of training and retention has interesting implications. For instance, if the cues inherent in the task are better perceived with 5-trial delay than with 0-trial delay in KR, as the earlier paper concludes (Lavery & Suddon, 1962), it can be expected that if KR is delayed, the amount of training received will determine the level of accuracy achieved in retention trials. In other words, if subjects are trained to use die cues which can be used in retention trials, retention should be a direct function of the amount of that type of training. On the other hand, if KR in training does not affect feedback which is available during retention trials, retention should not necessarily be affected by the number of trials done with that type of KR. In the earlier experimental results it was impossible to tell whether the level of acquisition, the number of trials in training, or both affected the level of retention. The level of accuracy reached at the end of training is not a variable which can easily be manipulated, because of the large differences among individual learning rates. For this reason an experiment was designed in which subjects were trained in either of two methods of KR (0-trial or 5-trial delay) while being given alternating series of knowledge (K) and no-knowledge (NK) trials of the same KR technique. The NK runs afforded a measure of retention resulting from the various numbers of training trials. It was expected that various levels of retention would result from different amounts of training under the 5-trial delay method and that one consistent level of retention would result from all the amounts of training received under 0-trail delay KR.

Sitmnzary.-The effect of knowing the eventuality of retention trials has been tested with three dicferent conditions and 56 female Ss. Ss who are told before training that they yill be tested without KR do better than Ss who are either told afrer training or not told at all. These results cast considerable doubt on the conclusions drawn from previous snidies that d o not mention explicirly what instructions, if any, were given regarding retention. The results of other studies done on KR variables are also discussed.