Effects of encoding strategy,presentation modality,and scoring method on STM performance with the Peterson and Peterson technique

The Peterson and Peterson (1959) STM experiment was replicated with variation of presentation modality and encoding strategy. The effect of various scoring criteria was also analyzed. The recall data showed that a Peterson and Peterson type forgetting curve was obtained using auditory presentation and instructions to rehearse vocally the trigrams when scoring only completely correct recall within the first 3 sec of the recall interval. With visual presentation and instructions to find meaningful trigram interpretations, the forgetting curve was higher and much more flat, especially when scoring position correct recall within the total 0-10-sec recall interval. In a buildup of PI experiment, no buildup of PI could be detected when visual presentation was used together with instructions to find meaningful trigram interpretations. The importance of the different encoding activities for recall performance was discussed.     

A study of position habits induced by reward and “frustration”

Predictions from Maier's theory of “frustration”-instigated behaviour have been tested in an experimental situation differing significantly from that in which the theory was propounded yet containing the central element of “frustration”—the insoluble problem.

A water discrimination unit was employed in which the performance of rats would be observed during attacks on insoluble problems, position problems or symbol problems.

Two groups, each containing ten Wistar albino rats, served as subjects. The research design consisted of the following phases: preliminary training, development of position responses, exposure to a symbol-reward problem with 50 per cent, punishment and exposure to a symbol-reward problem with 100 per cent, punishment. The design differed for the two groups only at the phase in which the position responses were established. During this phase one group was exposed to a position-reward problem and the other to an insoluble problem.

Position responses were established as frequently under position-“frustration” (position stereotypes) as under position-reward (position habits) conditions. Position stereotypes were more rigid—more resistant to extinction—than position habits under conditions of 50 per cent, punishment. Position stereotypes were as readily extinguished under 100 per cent, punishment as were position habits under 30 per cent, punishment.

The first two observations conform to predictions made from Maier's theory. The third does not. That is to say, not all situations containing the basic elements of “frustration” give rise to stereotyped behaviour patterns which are as rigid or “fixated” as Maier's theory would predict. It is a reasonable hypothesis that the characteristics of stereotyped responses established in certain “frustration” situations may be described adequately in terms of conventional learning principles without the necessity of resorting to a distinction between “goal-motivated” and “frustration-instigated” behaviour.     

Stimulus control of avoidance behavior

The introduction of a warning signal preceding shocks greatly increased the effectiveness of avoidance responding. Periods of “warm-up” at the beginning of the session were eliminated, and the number of shocks received by the subjects was greatly reduced. With response-shock interval constant, response rate increased as the interval between the response and the onset of the warning signal was shortened. The response tended to occur shortly after the onset of the warning signal regardless of the duration of these “safe” periods. A greatly elevated response rate was maintained even when the duration of the safe period was reduced to 0.3 sec. Thus, the pre-shock signal obtained nearly exclusive control of the responding and overrode the usual “temporal discrimination” of the response-shock interval.     

Stimulus generalization and the response-reinforcement contingency

Generalization gradients along a line-tilt continuum were obtained from groups of pigeons that had been trained to peck a key on different schedules of reinforcement. In Exp. I, gradients following training on a differential-reinforcement-of-low-rate (DRL) schedule proved to be much flatter than gradients following the usual 1-min variable interval (VI) training. In Exp. II, the value of the VI schedule itself was parametrically studied; Ss trained on long VI schedules (e.g., 4-min) produced much flatter gradients than Ss trained on short VI schedules (30-sec; 1-min). The results were interpreted mainly in terms of the relative control exerted by internal, proprioceptive cues on the different reinforcement schedules. Several implications of the results for other problems in the field of stimulus generalization are discussed.     

RECOVERY TIME AFTER GLARE: An experimental investigation of glare after-effect under night driving conditions

Preliminary experiments suggest that the changes in adaptation level due to glaring light in a night traffic meeting situation give no practically important deterioration of visibility. To obtain a more complete answer, one experiment was done in a 'real' night driving situation, and two experiments were carried out using a glare simulator, aimed at quantifying the change in the level of adaptation in terms of redetection time of a target made invisible due to glare. The effect of three factors were studied: duration of glare, maximum illuminance of glare, and contrast ratio between background and target. The preliminary suggestions were fully confirmed.     

Similarity effects in visual working memory

Perceptual similarity is an important property of multiple stimuli. Its computation supports a wide range of cognitive functions, including reasoning, categorization, and memory recognition. It is important, therefore, to determine why previous research has found conflicting effects of inter-item similarity on visual working memory. Studies reporting a similarity advantage have used simple stimuli whose similarity varied along a featural continuum. Studies reporting a similarity disadvantage have used complex stimuli from either a single or multiple categories. To elucidate stimulus conditions for similarity effects in visual working memory, we tested memory for complex stimuli (faces) whose similarity varied along a morph continuum. Participants encoded 3 morphs generated from a single face identity in the similar condition, or 3 morphs generated from different face identities in the dissimilar condition. After a brief delay, a test face appeared at one of the encoding locations for participants to make a same/different judgment. Two experiments showed that similarity enhanced memory accuracy without changing the response criterion. These findings support previous computational models that incorporate featural variance as a component of working memory load. They delineate limitations of models that emphasize cortical resources or response decisions.     

Health‐adjusted neuropsychological test norms based on 463 older Swedish car drivers

There is a need for improved normative information in particular for older persons. The present study provides neuropsychological test norms on seven cognitive tests used in a sample representing the general older driving population, when uncontrolled and controlled for physical health. A group of 463 healthy Swedish car drivers, aged 65 to 84 years, participated in a medical and neuropsychological examination. The latter included tests of visual scanning, mental shifting, visual spatial function, memory, reaction time, selective attention, and simultaneous capacity. Hierarchical regression analyses demonstrated that, when uncontrolled for health, old age was associated with significant impairment on all seven tests. Education was associated with a significant advantage for all tests except most reaction time subtests. Women outperformed men on selective attention. Controlling for health did not consistently change the associations with education, but generally weakened those with age, indicating rises in normative scores of up to 0.36 SD (residual). In terms of variance explained, impaired health predicted on average 2.5%, age 2.9%, education 2.1% and gender 0.1%. It was concluded (1) that individual regression‐based predictions of expected values have the advantage of allowing control for the impact of health on normative scores in addition to the adjustment for various demographic and performance‐related variables and (2) that health‐adjusted norms have the potential to classify functional status more accurately, to the extent that these norms diverge from norms uncontrolled for physical health.