Perceptual identification of visually degraded stimuli

In this article, we describe procedures, materials, and some representative results of a microcomputer-based approach to the degradation of visual stimuli for the investigation of perceptual identification. We discuss application of the procedures for the production of visually degraded picture, letter, and word stimuli, and of visual stimuli common to neuropsychological investigations.     

Interfering neighbours: the impact of novel word learning on the identification of visually similar words

We assessed the impact of visual similarity on written word identification by having participants learn new words (e.g. BANARA) that were neighbours of familiar words that previously had no neighbours (e.g. BANANA). Repeated exposure to these new words made it more difficult to semantically categorize the familiar words. There was some evidence of interference following an initial training phase, and clear evidence of interference the following day (without any additional training); interference was larger still following more training on the second day. These findings lend support to models of reading that include lexical competition as a key process.     

Unconscious processing of multiple nonadjacent letters in visually masked words

The claim that visually masked, unidentifiable ("subliminal") words are analyzed at the level of whole word meaning has been challenged by recent findings indicating that instead, analysis occurs mainly at the subword level. The present experiments examined possible limits on subword analysis. Experiment 1 obtained semantic priming from pleasant- and unpleasant-meaning subliminal words in which no individual letter contained diagnostic information about a word's evaluative valence; thus analysis must operate on information more complex than that contained in individual letters. Experiments 2 and 3 showed that analysis must operate on information more complex than that represented by individual bigrams (adjacent letters) or trigrams (three consecutive letters). These findings suggest that while subliminal priming is driven by subword analysis, the effective units of analysis are distributed widely across at least short (four- and five-letter) words.     

Bounding of letter sequences and the integration of visually presented words

Ss wrote down letters that were presented briefly in various temporal and geometric arrangements. Results reveal marked impairment in processing more than one temporally extended word in parallel. The impairment cannot be attributed to spatial separation of letters by itself, to sequence, or to inability to discriminate the letters. The concept of ‘bounding’ is introduced to account for the perception of familiar words in a continuing flow of information; the results suggest that only one object can be bounded at a time. They also suggest that the information that guides the eyes' movements in reading is qualitatively different from the information extracted from the printed text.     

Learning and retrieval rate of words presented auditorily and visually

Mode of presentation (visual or auditory) of a multitrial free recall test is stressed as an important factor in improving the diagnosis of certain neurological patients. For further use in neuropsychological research, an experiment was carried out using normal subjects, in which the effects of presentation mode and order of modality were investigated. There were no differential effects of these variables on several parameters, such as the number of words recalled and the learning curve. The time needed for the responses in immediate recall was the same in both auditory and visual conditions. In delayed recall, however, the interresponse times were significantly shorter when words had been presented auditorily than when presented visually. The results are discussed in light of further application in the field of neuropsychology.     

The role of eye movements in the perception of visually induced motion

Changes in eye position were recorded while S experienced visually induced motion. Movement of the eye was not found to correlate, in either direction or extent, with this type of apparent motion. Induced movement was explained, therefore, in terms of a change in phenomenal rather than retinal location.     

The role of eye movements in the perception of visually induced autokinesis

Changes in eye position were recorded physiologically while S experienced visually induced autokinesis. Eye movements did not seem to sufficiently explain this phenomenon. Apparent motion was found to be based upon a change in phenomenal rather than retinal location. Special consideration was given to those parameters possibly responsible for paradoxical motion.     

The role of elaboration in the persistence of awareness for degraded objects

When a fragmented line-drawing of an object moves relative to a background of randomly oriented lines, the previously hidden object can be segregated from the background and consequently enters awareness. In this shape-from-motion paradigm, the percept of the object briefly persists after the motion stops, demonstrating the maintenance of a bound percept in awareness. This study investigated how the manipulation of object features that are crucial to recognition influences both the binding process and the maintenance of objects in awareness. Overall, we found that objects that took longer to recognize (i.e., objects missing their vertices) were nonetheless maintained in awareness for longer. We argue that this effect is mediated by additional elaborative processing that is required to bind these less recognizable forms, which generates stronger and more robust representations. These representations are then more easily maintained in awareness, suggesting an important role of elaborative mechanisms for conscious representations.     

Letters and words in word identification

Studies by Barron and Henderson (1977) and Johnson (1975) provide evidence that whole words may be the unit of identification in word perception, rather than single letters. Johnson found that words were matched faster than a letter to the first letter in a word. Barron and Henderson found faster matching times for words than for legal non-word items in a letter-matching task. These findings support the interpretation that words are identified before individual letters. If so, a word-frequency effect should be expected. Experiments 1 and 2 tested for word vs. first-letter-in-word differences, as well as for a word-frequency effect in simultaneous and delayed visual matching tasks. In the simultaneous task, first letters in words were matched faster than words. In the delayed task, there was no difference between matching words or matching the first letters in words. With both tasks there was a word-frequency effect for word matches but not for first-letter-in-word matches. In Experiment 3, first-letter matching time was unrelated to word frequency or lexical status, although it did vary with orthographic legality. These results, on the whole, are consistent with a race model in which identifications take place simultaneously at word, letter-cluster, and letter levels, rather than a sequential model in which the whole word is identified before the component letters.     

The role of phonology in processing morphologically complex words

Psychonomic Bulletin & Review - This study investigated the role of phonology in the processing of morphologically complex words in a masked priming experiment. An English stem word target was...     

On the role of outline shape and word-specific visual pattern in the identification of function words: None

A common assumption in the reading literature is that function words are often identified wholly or in part on the basis of outline shape and/or word-specific visual pattern. This assumption was examined in three perceptual identification experiments, a speeded oral reading experiment, and in a lexical decision task where the visual pattern of function words and control items (content words, non-words and control strings) was systematically distorted by cAsE alTeRnA-tIoN. In all five experiments distortion failed to impair performance more on functors than on various control items. This result is argued to be inconsistent with the view that outline shape and word-specific visual pattern typically play a role in the identification of isolated function words.

Shape distortion impaired function words less than controls in perceptual identification, but impaired function and content words equally in speeded naming and lexical decision. These contrasting effects of shape distortion are discussed in terms of a distinction between the uptake of information (lexical access) and phenomenal perception.     

The role of attention in the associative binding of emotionally arousing words

In the present study, we examined the role of attention in modulating the memory benefit of emotional arousal for same-valence word pair associations. To assess the role of attention either at encoding or at retrieval, participants studied lists of positive, neutral, and negative words pairs under full attention, divided attention at encoding, or divided attention at retrieval, and then were tested on the single words and on the associations between words. Consistent with past studies, memory accuracy was higher for emotional items than for neutral items, and no memory difference was observed across emotional arousal conditions for associations when encoding occurred under full attention. In contrast, memory accuracy was higher for emotionally arousing items and associations relative to neutral items when encoding occurred under divided attention. Finally, dividing attention at retrieval revealed similar effects across emotion conditions, suggesting that retrieval of emotional stimuli relative to neutral stimuli, unlike encoding, does not benefit from automatic processing. The discussion emphasizes the role of automatic processing during encoding in producing the benefit of emotionally enhanced memory, as well as the extent to which controlled attention is responsible for eliminating or reversing (relative to neutral materials) emotionally enhanced memory for associations. Additionally, the implications of the divided-attention-at-retrieval manipulation include consideration of the way in which emotional items may be consciously processed during encoding.     

The role of bigram frequency in the perception of words and nonwords

Memory & Cognition - Adult subjects decided whether strings of four, five, or six letters formed words or nonwords. Words and nonwords were equally probable stimuli, and there were equal...     

The role of semantic transparency in the processing of English compound words

Experiment 1 examined whether the semantic transparency of an English unspaced compound word affected how long it took to process it in reading. Three types of opaque words were each compared with a matched set of transparent words (i.e. matched on the length and frequency of the constituents and the frequency of the word as a whole). Two sets of the opaque words were partially opaque: either the first constituent was not related to the meaning of the compound (opaque‐transparent) or the second constituent was not related to the meaning of the compound (transparent‐opaque). In the third set (opaque‐opaque), neither constituent was related to the meaning of the compound. For all three sets, there was no significant difference between the opaque and the transparent words on any eye‐movement measure. This replicates an earlier finding with Finnish compound words ( Pollatsek & Hyönä, 2005 ) and indicates that, although there is now abundant evidence that the component constituents play a role in the encoding of compound words, the meaning of the compound word is not constructed from the parts, at least for compound words for which a lexical entry exists. Experiment 2 used the same compounds but with a space between the constituents. This presentation resulted in a transparency effect, indicating that when an assembly route is ‘forced’, transparency does play a role.     

The role of the saccade target object in the perception of a visually stable world

Although the proximal stimulus shifts position on our retinae with each saccade, we perceive our world as stable and continuous. Most theories of visual stability implicitly assume a mechanism that spatially adjusts perceived locations associated with the retinal array by using, as a parameter, extra-retinal eye position information, a signal that encodes the size and direction of the saccade. The results from the experiment reported in this article challenge this idea. During a participant's saccade to a target object, one of the following was displaced: the entire scene, the target object, or the background behind the target object. Participants detected the displacement of the target object twice as frequently as the displacement of the entire background. The direction of displacement relative to the saccade also affected detectability. We use a new theory, the saccade target theory (McConkie & Currie, 1996), to interpret these results. This theory proposes that retinal (as opposed to extra-retinal) factors, primarily those concerning the saccade target object, are critical for the detection of intrasaccadic stimulus shifts.     

The role of morphological constituents in reading Finnish compound words

The processing of transparent Finnish compound words was investigated in 2 experiments in which eye movements were recorded while sentences were read silently. The frequency of the second constituent had a large influence (95 ms) on gaze duration on the target words, but its influence was relatively late in processing: A clear effect only occurred on the probability of a third fixation. The frequency of the whole compound word had a similar influence on gaze duration (82 ms) and influenced eye movements at least as rapidly as did the frequency of the second constituent. These results, together with an earlier finding that the frequency of the first constituent affected the first fixation duration, indicate that the identification of these compound words involves parallel processing of both morphological constituents and whole-word representations.     

Reading skill and the identification of words in discourse context

Word identification latencies and word prediction accuracy were compared for groups of skilled and less skilled young readers in three experiments. In each experiment, discourse context reduced identification latencies for less skilled as well as skilled readers. This was true both when context was heard and when it was read. The general relationship between word predictability and latency was the same for skilled readers and for less skilled readers, but only less skilled readers’ identification latencies were affected by word length and word frequency when the word appeared in context. When subjects predicted the word before identifying it, correctly predicted words were identified more quickly than words not predicted correctly, and skilled readers were more accurate in prediction than were less skilled readers. Although reading-related differences in the use of discourse context may characterize other aspects of reading comprehension, the use of context in identifying words is not a major source of reading difficulty.     

The effect of oral vocabulary on reading visually novel words: a comparison of the dual-route-cascaded and triangle frameworks

Dual-route-cascaded (DRC) (e.g. Coltheart & Rastle, Journal of Experimental Psychology: Human Perception and Performance 20 (1994) 1197) and triangle framework (e.g. Seidenberg & McClelland, Psychological Review 96 (1989) 523) predictions were tested regarding the effect of having a word in oral vocabulary prior to reading that same word. Over two sessions, at intervals of 2--3 days, 44 Grade 1 (6--7-year-old) children were aurally familiarized with the sound and meaning of ten novel words (semantic oral instantiation), and with just the sound of another ten novel words (non-semantic oral instantiation). Two to three days later non-word naming performance was significantly more accurate for aurally trained novel words compared to pseudohomophones, which were in turn advantaged over untrained non-words. The semantic manipulation had no effect. Experiment 2 manipulated articulation during (non-semantic) training. Forty Grade 1 children participated. Again, aurally trained items were named more accurately and quickly than equivalently trained pseudohomophones, which were in turn advantaged over untrained non-words. The articulation manipulation had no effect. The results suggest that word-specific phonological information is represented in the reading system independently of semantic or articulatory influences. The results are interpreted as being problematic for both the DRC and triangle frameworks, but more so for the latter.     

The role of attention in the preparation of visually guided eye movements in monkey and man

Summary Neurophysiological data from single cells in the monkey's visual association cortex as well as saccadic reaction time measurements in monkey and man are reported. When a monkey directs his attention to a peripheral light stimulus the visual activation of cortical cells responsive to that stimulus is increased. If visual attention is directed to a particular part of the visual field the saccadic reaction time is long (around 200 ms in monkey and above 200 ms in man). In contrast, if attention is disengaged from any location to which it might have been engaged before, monkeys and men can execute express saccades, that is, saccades after extremely short and stable reaction times (around 75 ms in monkey and 100 ms in man). The results are interpreted in the context of a hypothesis according to which the initiation of voluntary, visually guided saccades includes three premotor mechanisms: the computation of the target location, the decision to make a saccade, and the disengagement of attention.