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Biomedical subjects

J S Warm

Publications and source records attributed to J S Warm.

34 records · Page 2Linked to original sources
PubMed1983

Target recovery in visual backward masking: no clear explanation in sight.

Theories of visual backward masking have generally ignored demonstrations of the perceptual recovery of a masked target when the masking stimulus (M1) is followed by a second masking stimulus (M2). This failure to address recovery may reflect a belief that recovery effects are relatively small and inconsistent. The present article reports a series of experiments, using single-letter targets, a patterned M1 and a light-flash M2, which indicate that recovery can be a robust and substantial phenomenon. It is observable under a variety of conditions, and the magnitude of recovery matches the masking effect itself. A two-choice discrimination task was employed to test an explanation for recovery that attributes the effect to inhibition from the transient response to the light flash on the sustained response to the patterned mask. That explanation calls for the shape of the function relating the discriminability of the patterned mask to the onset asynchrony of M1 and M2 to be U-shaped in form. The data, however, reveal a monotonic masking function, suggesting that only sustained, intrachannel interactions are involved in the recovery of the target percept. Two conflicting explanations for recovery are discussed, one based upon inhibition of M1 responses, the other upon enhancement of target features. Thus, while recovery is demonstrated to be very real, its explanation remains elusive.

Adolescent↗
PubMed1983

Attentional processing and the subjective contour illusion.

Leading explanations of the subjective contour illusion can be classified as being either "bottom-up" or "top-down." Bottom-up explanations assert that peripheral, physiological mechanisms often associated with the perception of real contours also account for subjective contour (SC) perception. In contrast, top-down explanations posit a more central locus of SC perception and are formulated on a molar, psychological level. A major aspect of bottom-up perceptual processing is that it is largely automatic. On the other hand, top-down processing implies a greater role for selective attention. In an effort to distinguish between bottom-up and top-down accounts of SC perception, the present investigation used a dual-task paradigm to test the relative attentional demands of real contour perception versus SC perception. In the primary task, subjects made speeded same-different discriminations of either paired SC forms or their real contour analogues. Half the subjects performed this primary task in conjunction with a six-digit short-term memory load secondary task. If subjective forms indeed impose a greater limited-capacity processing load than real forms, then the need to share processing capacity with a secondary task was expected to produce a greater increment in reaction time (RT) for subjective relative to real forms. The results indicated that the expected enhanced RT increment for subjective relative to real forms with the addition of a concurrent memory load was limited to same trials. This result implies that the nature of response indicators must be considered in assessing capacity requirements with the sort of dual-task paradigm used in the present investigation. Nevertheless, the fact that the increment in same RT with the addition of a concurrent memory load was greater for subjective relative to real forms accords with expectations derived from the notion that the perception of SCs is more attention demanding than that of real contours. If the interpretation of the present study is correct, then a comprehensive theory of SC perception will most likely be formulated within the top-down perspective of conceptually driven visual information processing.

Adult↗
PubMedDate not supplied

Recent advances in the neuropsychology of human olfaction and anosmia.

Patients' olfactory functioning is rarely considered by rehabilitation specialists because this capacity is seen as unnecessary for most vocational and academic purposes. However, several recent studies have shown that intermittent exposure to fragrances can help subjects sustain attention more efficiently. As this effect is especially pronounced when subjects report attention-maintenance difficulties, accessory olfactory stimulation may enhance the sustained attention capacities of head-injured subjects. Another study is cited in which subjects who lost their sense of smell following head injuries were found to experience more difficulty in maintaining employment. This effect is probably related to orbital lobe damage, which usually accompanies post-traumatic anosmia. The implications of these studies for rehabilitation professionals are discussed.

Arousal↗