Automatic and Controlled Processes in the Analytisis of Hierarchical Structure

Targets are identified faster if they appear at the same level (global vs. local) as the target on the previous trial. This effect has been attributed to a controlled attentional process wherein participants attend to the level containing the target on trial n − 1, thus facilitating performance if target level repeats on trial n. An alternative explanation (Lamb & Yund, 1966) is that automatic activation of level-specific neural mechanisms is responsible. The controlled-process hypothesis predicts better performance whenever target level is predictable, because participants can anticipate, and thus attend to, the appropriate level. The automatic-process hypothesis predicts better performance when target level repeats, regardless of target-level predictability. In the present studies, level repetitions facilitated performance regardless of target-level predictability. The data support the automatic-process explanation of level repetition and other attentional effects. The data illustrate how an automatic process can give rise to performance that seems to reflect more cognitive or strategic mechanisms.     

Pupillary changes during encoding, storage, and retrieval of information.

6 subjects were each auditorily presented six lists of 7-digit numbers for retention intervals of 0, 5, and 10 sec. Pupil size was recorded during stimulus presentation, retention, interval, and recall of items. Results indicated that pupil dilation occurred during encoding and retrieval of stimulus items. Pupillary constriction was found during the retention interval when rehearsal was presumed to occur.     

Coding strategies,perceptual grouping,and the “variability effect” in free recall

Three experiments examined the effects of constant vs. varied input of letter strings on recall, and then examined the effects of such training in the learning of new lists of letter strings. Letter strings were constructed from pairs of trigrams spatially grouped, and were presented either consistently or with different spatial groupings on successive presentations. In Experiments I and II, varied input produced substantially greater recall than constant input. When transferred to a new list of letter strings, containing either the same general structure or a new scrambled structure, recall of the second list was determined primarily by conditions of first-list input, and unaffected by second-list structure. Although the "variability effect" did not appear in the training phase of Experiment III, Varied input led subjects to regroup or integrate the letter sequences more frequently and produced similar transfer effects as in Experiments I and II.     

On-line brain stimulation: Measurement of threshold of reinforcement

This program and interface for a small computer (PDP8/e) performs the following operations: generates and delivers constant current stimulation to the brain of an animal, monitors electrical resistance at the stimulating electrode, and calculates the threshold of reinforcement based upon the frequency of characteristic pauses in the animal’s responding.