Order of report and processing in tachistoscopic recognition

Two groups of 12 Ss were shown tachistoscopically 4 letters and 4 numbers. Within these alpha-numeric sequences, three variables were systematically manipulated: grouping of items, initial item, and familiarity of the letter sequences. One group of Ss reported first letters then numbers from each sequence; the other group reported numbers then letters. The results indicated that grouping, redundancy, and order of report had significant effects on letter accuracy but not on number accuracy. These effects were interpreted in terms of processing, particularly the use of spatial and identity information during recognition.     

The effect of prior recall on multiple response recognition

Certain investigators have found that recognition is impaired when a recall test is interpolated during the retention interval. One possible explanation of this finding is that interpolated recall leads subjects to employ a more stringent recognition criterion. In the two experiments reported here, the influence of the recognition criterion was eliminated by using a multiple-response test requiring subjects to rank a recognition list consisting of old and new items. Nevertheless recall impaired subsequent recognition in both experiments, the effect being most marked for lowly ranked items. The recognition test in the first experiment was carried out in two stages. This made possible a direct examination of whether recall has an effect on the recognition criterion. No evidence for such an effect was obtained. Other ways in which recall may affect the recognition criterion are discussed.     

Averaged occipital responses to stimulation of sites in the upper and lower halves of the retina

Averaged responses of the occipital lobes to flashes imposed along the midline of the upper part of the retina are larger and of shorter latency than responses to flashes imposed on the lower retina. Since reaction times also are shorter when the upper retina is stimulated, this study provides further evidence for the generalization that reaction time varies inversely with amplitude and directly with latency of the evoked response.     

Carbon dioxide as a reinforcer in escape conditioning

The effects of varying CO₂ concentration, and intervals between CO₂ presentations, were determined from the performance by five pigeons of a learned motor act which eliminates CO₂ from the inspired air. The length of time from the onset of an externally-produced increase in inspired CO₂ to the performance of the learned motor response terminating the CO₂ presentation was inversely related to the CO₂ concentration presented (3 per cent and 5 per cent) and directly related to the inter-trial interval (3 minutes and 1.5 minutes). Chemoreceptors on the ventrolateral surfaces of the medulla are postulated to be the initial site of stimulation in the chain of events leading to the behavioral bioregulation of inspired CO₂ concentration.