Visual interference in the parafoveal recognition of initial and final letters of words.

https://pure.tue.nl/ws/files/4267560/734493.pdf

Eccentric vision: adverse interactions between line segments.

Visual conspicuity and selective background interference in eccentric vision.

Slant-specific interference between line segments in eccentric vision was altered by attentional methods in hypnotically susceptible observers. These methods included negative and positive posthypnotic hallucination of the inducing elements of the array, and nonhypnotic instruction to actively ignore the elements. Contributions to the experimental effects apparently derived in part from intrinsic inhibitory or facilitatory skill in the individual observer, sharpened by hypnotic training in hallucinations. Control observers with low and with high hypnotic susceptibility were not able to alter significantly the interference effect when attempting to simulate the hallucination conditions. The results seemingly link these attentional alterations to an early cortical stage of visual processing.

Attentional alterations of slant-specific interference between line segments in eccentric vision.

In the previous paper (Beerens and Bouma, this issue) we have shown that in eccentric vision an adverse interaction between line-segments can be found which operates over the same distance as interaction between eccentrically presented letter stimuli. It is known that the interaction between letter stimuli in eccentric vision is asymmetrical around the test letters; the interaction is stronger if the interaction letter is on the peripheral side of the test letter rather than on the foveal side (Mackworth, 1965; Bouma, 1970). In this paper our aim is to show that the interaction between line stimuli is asymmetrical around the test stimulus with the same bias as found with letter stimuli, and that it seems possible to describe this asymmetry empirically by assuming the interaction to be symmetrical around the interaction stimulus. Furthermore, we have found indications that the form of the asymmetrical interaction area can be derived from the same assumption.

Asymmetry and symmetry in eccentric line interaction

In eccentric vision a stimulus letter presented singly is better recognisable than a stimulus letter which is flanked by other letters (Mackworth, 1965; Bouma 1969, 1970). This adverse interaction between letter stimuli was found to operate over relatively large visual angles P between test letter and flanking letters, Pm being about 0.5 ¢ (where Pm is the maximum value of P, and ¢ is the eccentricity of the testletter). Furthermore, indications were found (Bouma, unpublished) that this interaction might depend on similarities in shape between testletter and flanking letters. These findings gave rise to a further investigation of the nature of interactions in eccentric form recognition. Here we present evidence for the subjoined conclusions. Interactions in eccentric vision are not restricted to letter stimuli; they may also be found with much simpler forms, such as line-segments (figs. la and lb). One of the factors involved in interactions between line-segments is the difference in orientation between test stimulus and interaction stimulus. The ratio Pm/¢ that can be found for equally orientated same order as that found in letter interaction.

Egj Beerens

Papers

Asymmetry and symmetry in eccentric line interaction

Orientational specificity of line interactions in eccentric vision

Interaction between lines in eccentric vision : contrast treshold and just noticeable difference in slant