Lloyd L. Avant

Effects of stimulus familiarity upon judged visual duration

Five experiments investigated the influence of the differences in stimulus familiarity among a dot-matrix letter, word, and nonword upon the relative judged duration of 30-msec flashes. Figure-ground contrast was manipulated by varying the number of dots comprising each display letter. With 30-msec presentations, judgments ranked subjective durations of the displays nonword > word > letter. Differences in judged duration among stimulus forms were greater when both forward and backward masking reduced recognition probability to chance level than when no mask was employed, and discriminations among masked presentations were easier for subjects. Figure-ground contrast influenced apparent duration judgments only as increases in figure-ground contrast contributed to clarity of familiarity differences among displays. The data were interpreted to indicate that differences in stimulus familiarity operate as early in visual processing as do differences in figure-ground contrast, with greater familiarity facilitating an automatic contact between a stimulus and its memory representation and therein reducing experienced duration.

Alcohol impairs visual presence/absence detection more for females than for males

Ninety subjects (45 males, 45 females) were given 0.0, 0.5, or 1.0 ml/kg body weight of 190-proof ethanol and tested for chance-level presence/absence detection thresholds with energy-masked presentations of traffic signs and blank inputs. Alcohol produced higher blood alcohol concentration (BAC) levels, and higher detection threshold durations, for females than for males. These results indicate that alcohol influences precortical visual processing and that the influence is greater for females than for males. The higher bioavailability of alcohol in women is likely due to less gastric oxidation of ethanol in women than in men.

On visual access to letter case and lexical/semantic information

Four experiments were designed to investigate automatic processing of letter case and lexical/ semantic information under forward and backward masking conditions that disallowed a visible image. Stimulus displays were letter string pairs; the letter case for each pair matched or mismatched, and the relationship between the two strings within pairs varied. Experiment I required direct Same-Different responses to stimulus pairs, and the results indicate that tasks requiring direct responses to stimulus inputs cannot distinguish between conscious response biases and unconscious use of information. Experiments 2 and 3 employed an indirect index of automatic prerecognition analyses of verbal-linguistic parameters and showed that, with 30-msec pre- and postmasked presentations, letter case, orthographic regularity, and lexical/semantic information are all analyzed in unconscious operations. Experiment 4 demonstrated that, under the viewing conditions of Experiments 2 and 3, subjects had no awareness of the stimulus input.

Perceived tachistoscopic duration and early visual processing in preschool children and adults

Abstract Two experiments further explored the Avant et al. (1975) finding that stimulus familiarity influences prerecognition processing to generate differences in the apparent duration of tachistoscopic flashes. The first experiment tested for developmental differences in the effects of upright versus 90°, 180°, and 270° rotations of a single letter or number upon the apparent duration of pre- and postmasked 30- and 50-msec flashes with adults and 4- and 5-year-old children. All age groups judged upright presentations to be of briefer duration. These differences in apparent duration were interpreted to index the automaticity of contacts between stimulus inputs and their memory representations. Failure of the children to recognize the letter and number in any orientation indicates that contact between stimulus inputs and memory representations precedes allocation of attention to the presented stimulus. The second experiment explored the influence of spatial structures which are not coded verbally by testing effects of good and poor dot pattern Gestalts on the apparent duration of tachistoscopic flashes. Adults discriminated between apparent durations of good and poor Gestalts but 4- and 5-year-olds did not. Apparent duration differences in the two experiments showed that spatial pattern structure and familiarity with verbal stimuli influence early visual processing in different ways.

Contrast and assimilation effects in judgments of line configurations containing the Mueller-Lyer figure

Two experiments are reported in which contrast and assimilation effects of anchor line lengths upon focal line lengths were observed. In Experiment 1 straight-line anchors shorter than, and parallel to, focal Mueller-Lyer figures made the figures appear shorter than the same Mueller-Lyers anchored by straight lines longer than the figures. In Experiment 2, focal stimuli were straight lines and parallel anchors were Mueller-Lyer figures. When focal length approximated anchor length, judged length of the focal stimulus was less if anchoring Mueller-Lyers had inward obliques than if the obliques pointed outward. However, as focal length deviated from anchor length, this effect of Mueller-Lyer obliques reversed; outward obliques made focal lines appear shorter than did inward obliques. Results are discussed in terms of adaptation-level theory (A-L theory).

The role of the thematic relationship between focal and contextual stimuli in recall

Three experiments, involving a total of 298 Ss, examined the effect of varying the level of thematic relationship between focal and background stimuli upon recall of the former. In all experiments the focal stimuli were colored pictures of common objects. In Exps. I and III the background stimuli were also pictures of common objects; in Exp. II, they were the names of these objects. In Exps. I and II, tests involved free recall of the class names of the focal stimuli; in Exp. III the background stimuli were used as test stimuli and the required response was the specific name of the focal stimulus. Three levels of thematic relationship—focal and background stimuli were drawn from the same generic class, from a broader related group, or were selected at random—obtained in all experiments. The control condition for Exps. I and II involved presentation of the focal stimuli alone. In Exp. I, the presence of pictorial background stimuli of the same generic class as the focal stimuli had no reliable effect upon the free recall of the latter; however, with background stimuli of lesser relationship, performance was degraded when compared to the control condition. In Exp. II, the presence of verbal background stimuli was found to have no effect upon free recall. In Exp. III, associative recall of specific names was directly related to level of thematic relationship between focal and background stimuli.

On the left and right hemisphere visual processing that precedes recognition

Three experiments, and a replication of each, investigated the nonconscious prerecognition visual processing given left visual field (LVF) and right visual field (RVF) letter inputs. Each input was a vertically arrayed pair of letters in which three variables were manipulated: (1) the same letter twice vs one each of two letters, (2) same vs 180 degree difference in orientations within each letter pair, and (3) normal vs mirror-image letter form. The procedure presented all pairs of letter combinations in pairs of pre- and postmasked 10-msec flashes; the subjects task was to report which flash of each pair appeared to last longer. When letter pairs differed on all three variables, RVF presentations of mirror-image letters were judged to be longer than equal presentations of normal letters; the reverse occurred for LVF presentations. When one normal and mirror-image letter were presented, RVF presentations of mismatched orientations were judged to be longer than matched orientations, and the reverse was true for LVF presentations. When pairs of two normal letters were presented, no processing difference between LVF and RVF presentations was observed. A fourth experiment tested presence/absence detection of the letter pairs under the input conditions of the main experiments and showed those conditions to produce chance-level presence/absence detection. These results suggest that each hemisphere can perform its own prerecognition operations and that neither hemisphere is necessarily specialized for any particular prerecognition visual operation.

THE EFFECT OF RELATED AND UNRELATED MEMORY LOADS ON THE PRERECOGNITION VISUAL PROCESSING OF TRAFFIC SIGNS.

Prerecognition visual processing of traffic signs was evaluated while subjects maintained one of four different types of memory load: low imageability nouns, traffic sign words, random shapes, or traffic sign shapes. Recall was uniformly high (mean=92%) and did not differ among groups. There was a highly significant interaction among groups (different memory loads), sign messages (Stop, Right, Left, Slow), and sign formats (symbol vs. word). Holding random shapes in memory eliminated prerecognition processing differences among sign messages for symbol format signs. However, for all other memory loads, differences among sign messages were significant. Tests across the memory load conditions for each format of each sign message showed that, for the Stop symbol, the Right symbol, and the Right word signs, the various memory load conditions produced no significant differences. For all other sign messages in both symbol and word format, there were significant differences among memory loads. In summary, these data show that the action message presented in traffic signs is being unconsciously processed within the first few milliseconds of visual processing, and that these operations involve unconscious activation of memory processes that store the meanings of various signs.