The Poggendorff illusion: Apparent misalignment which is not attributable to apparent orientation of the transversals

Subjects while looking down were required to adjust a horizontal field of parallel lines (Experiment I) or a single line (Experiment II) to the apparent sagittal direction with and without a superimposed rectangle in the centre of a circular field. The rectangle was tilted at 20, 30 or 40° to the parallels and at 20° to the line. For the 20° condition the parallel lines were apparently oriented at about half a degree compared with the field without a rectangle but in the direction opposite to that necessary to account for the Poggendorff misalignment effect. For the 30 and 40° conditions the lines did not change in apparent orientation. The orientation of the single line did not change. Almost all subjects readily reported an apparent misalignment between the collinear parallels and line separated by the oblique rectangle. It is concluded that the Poggendorff misalignment illusion occurs without apparent regression of the lines to right angles with the figure.     

Preference and response suppression under different correlations between shock and a positive reinforcer in rats

A lever-press response by rats was reinforced by food in two successively presented types of trial signalled by different discriminative stimuli. When responding was punished by a shock in one type of trial, a groups for which the shock always preceded the reinforcer by .5 sec (positive correlation) showed less suppression in those trials than a group which received the shock and food separated in time (negative correlation). When, in a second experiment, rats were given a choice between food alone in one end of a shuttle box and either positively or negatively correlated shock and food in the other on a concurrent schedule, the group receiving the negatively correlated shock showed a greater preference for the food alone end. On the basis of a third experiment in which a tone was substituted for the shock in the choice situation, it was argued that the effect of correlation was not simply due to the stimulus properties of the shock. A final experiment demonstrated that when shock punishment is administered during extinction of the lever-press response, the rate of extinction is slower if the shock has been previously paired with the food reinforcer. Pairing a shock with food seems to attenuate the intrinsic aversiveness of the shock through Pavlovian counterconditioning.     

Adaptation level as an explanation of the peak shift in generalization with movement stimuli

Two experiments examine the value of adaptation level theory as an explanation of the peak shift phenomenon in stimulus generalization using linear arm movements. The first experiment manipulates the differences in adaptation levels during training by varying the frequency of experience of the training stimulus. Significant shifts in the peaks of generalization gradients were subsequently identified. The peak shifts were in the direction predicted by adaptation level theory. The second experiment manipulates testing adaptation levels by biasing the generalization test movements. Three groups of subjects performed differentially weighted test sequences in which the relative number of short, medium, or long movements was manipulated. Significant peak shifts of generalization gradients were observed in the direction predicted by adaptation level theory.     

Warm- and fatigue in skill acquisition and performance

Two experiments examined the effects of preliminary exercise on performance and learning of the Fitts' reciprocal tapping task. In the first experiment preliminary exercise was performed with either the preferred or nonpreferred arm. The tapping task was completed with the preferred by both groups. Low levels of preliminary exercise resulted in heightened performance for both groups, but higher levels resulted in a decrement for the group using the preferred arm. An arousal-plus-fatigue hypothesis can explain the results. A subsequent post-test without preliminary exercise showed no difference between the groups, indicating an effect on performance and not learning. In the second experiment preliminary exercise was provided by treadmill running to exhaustion. Again, a facilitatory effect of exercise was demonstrated on tapping performance even after exhaustive levels of running.     

Post-trial stimulation and the acquisition of conditioned suppression in the rat

Three experiments investigated the effect of post-trial stimulation on conditioning. Rats were trained in a conditioned suppression procedure in which only half of the CS presentations were followed immediately by a shock reinforcer. Presenting a second, post-trial, shock 8 s after the end of reinforced CS presentations increased resistance to extinction in Experiment I and facilitated conditioning in Experiment II relative to a condition in which the same post-trial shock was delivered 8 s after non-reinforced trials. Experiment III demonstrated that prior exposure to pairings of the shock reinforcer and the post-trial shock also enhanced subsequent conditioning, and thus ruled out an explanation of the facilitation in terms of the surprising nature of the post-trial stimulation.     

Marking rejected distractors: A gaze-contingent technique for measuring memory during search

There is a debate among search theorists as to whether search exploits a memory for rejected distractors. We addressed this question by monitoring eye movements and explicitly marking objects visited by gaze during search. If search is memoryless, markers might be used to reduce distractor reinspections and improve search efficiency, relative to a no-marking baseline. However, if search already uses distractor memory, there should be no differences between marking and no-marking conditions. In four experiments, with stimuli ranging from Os and Qs to realistic scenes, two consistent data patterns emerged: (1) Marking rejected distractors produced no systematic benefit for search efficiency, as measured by reinspections, reaction times, or errors, and (2) distractor reinspection rates were, overall, extremely low. These results suggest that search uses a memory for rejected distractors, at least in those many real-world search tasks in which gaze is free to move.     

Using a taped intervention to improve kindergarten students' number identification

A multiple baseline design across students was used to evaluate the effects of a taped numbers (TN) intervention on the number‐identification accuracy of 4 kindergarten students. During TN, students attempted to name the numbers 0 through 9 on randomized lists before each number was provided via a tape player 2 s later. All 4 students showed immediate increases and reached 100% in number‐identification accuracy. One student reached 100% accuracy after TN was supplemented with performance feedback, reinforcement, and overcorrection.