Do masks terminate the icon?

Iconic memory is operationally defined by part-report experiments (Sperling, 1960). If a mask is presented after the target, the mask is thought to be superposed on the target in the iconic representation, or to displace it from the representation. But could a cue presented after a pattern mask still allow selection within the target array? A target array of letters was followed by a checkerboard mask. We compared two target-mask interstimulus intervals (ISIs; 0 and 100 ms), and six cue delays. At ISI = 0 ms, performance was at chance, for part report and whole report. At ISI = 100 ms, with the shortest cue delay, observers demonstrated a part-report advantage of 25-30%. As cue delay increased the part-report advantage decreased. These results are inconsistent with an iconic memory that is automatically displaced or overwritten by new information. We consider two alternatives: a second-stage store, which represents letters in terms of their high-level features and which the mask cannot penetrate, or a four-dimensional store that preserves separately the representations of the target and its aftercoming mask. We discuss the implications of our results for studies that use backward masking to "terminate the icon".     

On the disruption of visual memory: Interference produced by visual report cues

Report of single letters from centrally-fixated, seven-letter, target rows was probed by either auditory or visual cues. The target rows were presented for 100 ms, and the report cues were single digits which indicated the spatial location of a letter. In three separate experiments, report was always better with the auditory cues. The advantage for the auditory cues was maintained both when target rows were masked by a patterned stimulus and when the auditory cues were presented 500 ms later than comparable visual cues. The results indicate that visual cues produce modality-specific interference which operates at a level of processing beyond iconic representation.     

Early and late selection in partial report: Evidence from degraded displays

In studies of iconic memory using the bar-probe task, subjects see a brief display of target letters and are probed by an arrow to report one of them. According to the classic early-selection account, subjects use the probe to select material for perceptual analysis from a precategorical (iconic) memory, but according to late-selection theories, subjects first identify the letters and then use the probe to select one letter for report from the set of categorized items. Pashler (1984) based his test for the locus of selection on a manipulation of display quality in previewed displays. He presented a target for 200 msec and then added a probe, together with the target, for an additional 150 msec. Reducing the target’s stimulus quality increased response latency. If the subjects identified the characters before the probe appeared and then selected an item for report, the clarity of the original array should not have affected response latency. Hence, Pashler concluded that his subjects used the probe to select from a precategorical store (early selection). Pashler’s experiment did not force subjects to rely on memory of the target; hence, although his experiment documented a situation in which subjects used early selection, it did not rule out late selection in studies of information persistence. We replicated Pashler’s findings and, using his logic, showed that when subjects are forced to rely on memory of the target, they select from a categorized store.     

Early and late selection in partial report: evidence from degraded displays.

In studies of iconic memory using the bar-probe task, subjects see a brief display of target letters and are probed by an arrow to report one of them. According to the classic early-selection account, subjects use the probe to select material for perceptual analysis from a precategorical (iconic) memory, but according to late-selection theories, subjects first identify the letters and then use the probe to select one letter for report from the set of categorized items. Pashler (1984) based his test for the locus of selection on a manipulation of display quality in previewed displays. He presented a target for 200 msec and then added a probe, together with the target, for an additional 150 msec. Reducing the target's stimulus quality increased response latency. If the subjects identified the characters before the probe appeared and then selected an item for report, the clarity of the original array should not have affected response latency. Hence, Pashler concluded that his subjects used the probe to select from a precategorical store (early selection). Pashler's experiment did not force subjects to rely on memory of the target; hence, although his experiment documented a situation in which subjects used early selection, it did not rule out late selection in studies of information persistence. We replicated Pashler's findings and, using his logic, showed that when subjects are forced to rely on memory of the target, they select from a categorized store.     

When expectation confounds iconic memory

In response to the methodological criticism (Bachmann & Aru, 2015) of the interpretation of their earlier experimental results (Mack, Erol, & Clarke, 2015) Mack, Erol, Clarke, and Bert (2016) presented new results that they interpret again in favor of the stance that an attention-free phenomenal iconic store does not exist. Here we once more question their conclusions. When their subjects were unexpectedly asked to report the letters instead of the post-cued circles in the 101th trial where letters were actually absent, they likely failed to see the empty display area because prior experience with letters in the preceding trials produced expectancy based illusory experience of letter-like objects.     

Spatiotopic and retinotopic components of iconic memory

Summary Recently, there has been considerable interest in whether information in iconic memory is stored in retinotopic or spatiotopic coordinates. The present experiment examined the issue using a masking paradigm. In one set of conditions, subjects maintained fixation while a row of four letters appeared for 19 ms, centered about three degrees to the right of fixation. After a 153 ms ISI, the letters were followed by a blank field (no mask), a mask in the same position as the letters, or a mask displaced three degrees to the right of the letters. In a second set of conditions, the stimuli were the same but subjects were asked to shift fixation from the fixation point to the middle of the letter row during the interval between the letters and the mask. Subjects' eye movements were monitored in all conditions. Accuracy of report for the letters was lowered only with the mask over the letters with the no-eye-movement conditions and in both masking conditions with the eye movements. The results suggest that the icon includes two components, one that is retinotopic and one that is spatiotopic.     

Short-term retention of superimposed and of spatially distinct multiletter visual arrays

On each trial, Ss attempted to retain a series of five visually presented letters while concurrently “shadowing” (repeating aloud) a rapid series of aurally presented letters. If serial-position accuracy is ignored, they were able to store more than only the last letter of a typical series, even though all five letters appeared on the same screen, and that performance was superior to the retention of five auditorily presented letters. Together, these findings suggest that a form of visual storage might have been employed for the retention of visual stimuli and, specifically, one that was relatively immune to erasure as compared to “iconic” storage. In further support of that hypothesis, retention of such visual series as measured by free-recall accuracy was not inferior to that of five letters, each of which was presented on a separate screen.     

Attentional factors in iconic memory and visible persistence

Arrays of 12 fragmentary letters were followed, at various intervals, by one randomly selected complementary letter fragment. On half the trials a partial-report cue (a vertical bar-marker) coincided with the second completion fragment. In Experiment 1 subjects fixated the centre of the to-be-identified letter location, whereas in Experiment 2 subjects fixated the centre of the array. In Experiment 1, the degree of integration and time between successive fragments were inversely related. Integration of fragmentary letters in Experiment 2, however, was uniformly low in the experimental and guessing control conditions. The results were discussed in terms of recent non-traditional accounts of iconic storage that emphasize post-categorical processing.     

Expectation creates something out of nothing: The role of attention in iconic memory reconsidered

Conscious experience is modulated by attention and expectation, yet is believed to be independent of attention. The experiments on iconic memory (IM) are usually taken as support for this claim. However, a recent experiment demonstrated that when attention is diverted away from the IM letter display subjects fail to see the absence of IM letters. Here we contribute to the ongoing debate by overcoming experimental shortcomings of this previous experiment, by measuring subjective visibility and by testing the effect of the post-cue. We were able to replicate these earlier findings and extend them by demonstrating that subjects who do not realize the absence of letters perceive illusory letters. This result means that there is still phenomenal consciousness, even when attention is diverted. Expectation creates illusory content that overwrites valid IM content. Taken together these findings suggest that the present experimental paradigm is not appropriate to make claims about IM content.     

Effects of noise letters on decisions: Discrete or continuous flow of information?

Four forced-choice letter-detection experiments examined the effect on detection latency of noise letters that were visually similar to target letters. A single target letter was present in each display. Noise letters were similar to the target letter present in the display (the signal), to a different target letter assigned to the same response as the signal, or to a target letter assigned to the opposite response from the signal. Noise letters were present in either relevant or irrelevant display positions, and two quite different stimulus sets were used. The experiments were designed to test a prediction of models in which information about noise letters is transmitted continuously from the recognition to the decision process. These models predict that responses should be faster when noise letters are visually similar to a target assigned to the same response as the signal than when noise letters are similar to a target assigned to the opposite response. Statistically reliable effects of the type predicted by continuous models were obtained when noise letters appeared in relevant display positions, but not when they appeared in irrelevant positions.     

Apes' use of iconic cues in the object-choice task

In previous studies great apes have shown little ability to locate hidden food using a physical marker placed by a human directly on the target location. In this study, we hypothesized that the perceptual similarity between an iconic cue and the hidden reward (baited container) would help apes to infer the location of the food. In the first two experiments, we found that if an iconic cue is given in addition to a spatial/indexical cue - e.g., picture or replica of a banana placed on the target location - apes (chimpanzees, bonobos, orangutans, gorillas) as a group performed above chance. However, we also found in two further experiments that when iconic cues were given on their own without spatial/indexical information (iconic cue held up by human with no diagnostic spatial/indexical information), the apes were back to chance performance. Our overall conclusion is that although iconic information helps apes in the process of searching hidden food, the poor performance found in the last two experiments is due to apes' lack of understanding of the informative (cooperative) communicative intention of the experimenter.     

Effects of iconicity and semantic relatedness on lexical access in american sign language

Iconicity is a property that pervades the lexicon of many sign languages, including American Sign Language (ASL). Iconic signs exhibit a motivated, nonarbitrary mapping between the form of the sign and its meaning. We investigated whether iconicity enhances semantic priming effects for ASL and whether iconic signs are recognized more quickly than noniconic signs are (controlling for strength of iconicity, semantic relatedness, familiarity, and imageability). Twenty deaf signers made lexical decisions to the 2nd item of a prime-target pair. Iconic target signs were preceded by prime signs that were (a) iconic and semantically related, (b) noniconic and semantically related, or (c) semantically unrelated. In addition, a set of noniconic target signs was preceded by semantically unrelated primes. Significant facilitation was observed for target signs when they were preceded by semantically related primes. However, iconicity did not increase the priming effect (e.g., the target sign PIANO was primed equally by the iconic sign GUITAR and the noniconic sign MUSIC). In addition, iconic signs were not recognized faster or more accurately than were noniconic signs. These results confirm the existence of semantic priming for sign language and suggest that iconicity does not play a robust role in online lexical processing.     

Improvement, learning and retention of skill at visual search

Three experiments examined factors responsible for improvement in visual search. In Experiment I three groups of subjects were each trained for 3000 trials to search for a particular set of target letters among a particular set of background letters. After intervals of 2, 4, or 6 weeks without further practice they were re-tested, either with the same displays or on new displays which they searched for the same target items among new background items. Negative transfer suggested that memory for specific cue-systems distinguishing target from background letters is retained for as long as 4 weeks.

Experiment II examined performance of three very highly practised subjects. After 25 days practice, variations in the size of the target set no longer affected search time. This could not be explained by learning of specific cue systems, since after this amount of practice subjects showed perfect transfer to displays which they searched for the same target items among new background items. Experiment III suggested that practised subjects achieve this high level of competence by learning to make two independent successive decisions, first to locate any member of the target set on the display and next to identify which particular member of the target set has been located.     

The role of letter identity and letter position in orthographic priming.

Four experiments are reported investigating orthographic priming effects in French by varying the number and the position of letters shared by prime and target stimuli. Using both standard masked priming and the novel incremental priming technique (Jacobs, Grainger, & Ferrand, 1995), it is shown that net priming effects are affected not only by the number of letters shared by prime and target stimuli but also by the number of letters in the prime not present in the target. Several null results are thus explained as a tradeoff between the facilitation generated by common letters and the inhibition generated by different letters. Inhibition was significantly reduced when different letters were replaced by nonalphabetic symbols. Facilitation effects disappeared when the common letters did not have the same relative position in the prime and target strings, thus supporting a relative-position coding scheme for letters in words.     

The role of letter identity and letter position in orthographic priming

Four experiments are reported investigating orthographic priming effects in French by varying the number and the position of letters shared by prime and target stimuli. Using both standard masked priming and the novel incremental priming technique (Jacobs, Grainger, & Ferrand, 1995), it is shown that net priming effects are affected not only by the number of letters shared by prime and target stimuli but also by the number of letters in the prime not present in the target. Several null results are thus explained as a tradeoff between the facilitation generated by common letters and the inhibition generated by different letters. Inhibition was significantly reduced when different letters were replaced by nonalphabetic symbols. Facilitation effects disappeared when the common letters did not have the same relative position in the prime and target strings, thus supporting a relative-position coding scheme for letters in words.     

Iconic reading in a case of alexia without agraphia caused by a brain tumor: a tachistoscopic study

The lack of nonverbal reading comprehension in the clinical disconnection syndrome, alexia without agraphia, has been contradictory to the relative reading comprehension of the right hemisphere in split brains. We report a 39-year-old patient with verbal alexia without agraphia caused by brain tumor. On rapid tachistoscopic presentation of object names, he denied seeing anything but showed nonverbal reading comprehension by pointing to the corresponding objects. He lost this ability when he recovered ability to name individual letters of the object names. Our results suggest that even partial verbal reading such as the naming of single letters makes demonstration of iconic reading impossible and that total functional disconnection from verbalization, as initially noted in this case or in split brain studies, is necessary to show nonverbal reading comprehension.     

The salience of silent letters in children’s memory for word spellings

To compare children’s memory for silent and pronounced letters in familiar spellings of words, 7- to 10-year-olds were given two tasks. First, they imagined word spellings and decided whether target letters were present. Then they recalled the words associated with the target letters. Five experiments yielded similar findings. Pronounced letters were recognized somewhat more accurately than silent letters. However, silent letters were detected more rapidly in words than pronounced letters were, and silent letters prompted superior recall of words. The influence of several factors, such as the particular words chosen, the position of letters, and the expectancies of subjects, was ruled out in one or another experiment. Two explanations for findings are proposed. The favorite is that effects reflect the way silent letters are stored in long-term memory when spellings are learned. The other is that events occurring in the experiment enhanced episodic memory for silent letters.     

Reducing the effects of adjacent distractors by narrowing attention.

Three experiments explored the gradual narrowing of visual attention to a letter target when other letters were positioned close by. The method by which attention was narrowed involved presenting a digit target immediately prior to the latter target and in the same location for progressively shorter durations and requiring the subject to identify both the digit target and the letter target before responding. The response time data from the first 2 experiments indicated that shorter durations of the digit reduced the amount of information processed from noise letters positioned on either side of the letter target. In the third experiment, in which separation of letters was increased slightly, the response times indicated that the information from flanking noise letters may have been virtually eliminated.     

Neon colors illuminate reading units

The effect of syllable-size reading units on neon color was investigated in 6 experiments. The stimuli consisted of 5- or 7-letter words or pseudowords with a syllable break either just before or just after the middle (target) letter. The target letter was overlaid with a plaid of red and green lines that gave it an ambiguous neon color. The letters preceding the target were overlaid with a monochromatic grid (red or green), and the letters following the target were overlaid with the other color. Ss were significantly more likely to judge the target as more similar to the color of other letters within its syllable than colors of letters outside that unit. The effect was shown not to be an artifact of guessing strategy or eye movements. Word structure determined by orthography and morphology affected neon colors, but no effect was found for purely phonological units.