Semantic priming: subliminal perception or context?

Briefly presented, masked priming stimuli that cannot be identified by themselves can affect the processing of subsequent targets. The effect, which is sometimes viewed as a demonstration of unconscious processing, has been linked to the subliminal perception literature. Experiments 1 and 2 indicated that the identification of primes in the context of semantically related targets is superior to the identification of primes presented alone, and that the identification of primes in the context of semantically unrelated targets is inferior to the identification of primes presented alone. Experiment 3 indicated parallel findings in a recognition task. Consequently, an explanation of semantic priming in terms of the interactive nature of stimuli that are near to one another in time seems preferable to one based upon concepts of unconscious processing and subliminal perception.     

Some errors of perceptual analysis in visual search can be detected and corrected

This experiment tried to discover whether people can correct errors which occur because they incorrectly analyse a display to which they have to respond--whether, in fact, they can correct “perceptual” as well as “motor” errors. In a serial, self-paced visual search task, subjects made one response to indicate that a display of five or nine letters contained either of a pair of target letters, and another response when no target was present. Omission errors were much more common than False Identification Errors, but more of them were corrected. Omission errors were detected and corrected faster than False Identification Errors. Typically omission errors were slow responses while False Identification Errors were fast responses. It is possible to deduce that at least some errors resulting from incorrect analysis of a display can be detected and corrected, probably because of an extension of perceptual analysis during, or immediately after, the time when a response to the display is made.     

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.     

Ordinal representation of numeric quantities by brown capuchin monkeys (Cebus apella)

Using techniques established by E. M. Brannon and H. S. Terrace (2000) with rhesus macaques (Macaca mulatta), the authors tested the ability of brown capuchins (Cebus apella) to order arrays of items ranging in quantity from 1 to 9. Three monkeys were trained on a touch screen to select the quantities 1-4 in ascending order. The monkeys exhibited successful transfer of this ability to novel representations of the quantities 1-4 and to pairs of the novel quantities 5-9. Patterns of responding with respect to numeric distance and magnitude were similar to those seen in human subjects, suggesting the use of similar psychological processes. The capuchins demonstrated an ordinal representation of quantity equivalent to that shown in Old World monkeys.     

After-effects of responding and of withholding responses in C.RT tasks

The effects of response repetition on choice RT were compared in b-reaction and in c-reaction tasks [Experiments I(a) and I(b)]. The difference in RTs for repeated and for non-repeated responses was found to be less for c-reaction than for b-reaction tasks. This seemed to be because in c-reaction tasks subjects can prepare themselves to make the same response on every trial, so that there is little further RT reduction consequent on immediate response repetition. In b-reaction tasks subjects cannot always prepare to make the same response, so that the difference between response repetition RT and responce alteration RT is greater. Experiment II examined transitions between events in a serial, self-paced C.RT task in which subjects made a different response to each of two signals but withheld any response to the onset of a third. In this task responses were faster when they followed other, different responses than when they followed “no go” trials. The results of these experiments allow us to reject, even for very elementary tasks, a simple “S--R connection network” model for the processes involved in the identification of signals and the production of responses to them.     

Actively Controlling Anticipation of Irregular Events

There have been no investigations as to how people respond to sequences of events which occur at brief, unpredictable intervals as in everyday life. Eleven young adults were practised at a two-choice, continuous, serial choice-response task in which intervals between each response and the onset of the next signal (RSIs) varied randomly from trial to trial. On half the trials in each of four conditions the RSI was 20 ms, and on the other trials 200, 400, 800 and 1600 ms respectively. Reaction times fell as RSIs increased from 20-200 ms but thereafter appeared to be unaffected by RSI duration. In the 20/200 and 20/400 ms RSI conditions RT was not affected by transitions between different RSIs but in the 20/800 and 20/1600 ms conditions RTs were faster when the longer RSI recurred on immediately successive trials than if the long RSI followed the short (20 ms) RSI. These results are discussed in terms of a control system model for the way in which subjects actively trade off between their internal performance limitations to optimally meet task demands.     

Modulation of selective attention by sequential effects in visual search tasks

In visual search detection of a target on one display facilitates its subsequent recognition on the next (Rabbitt, Cumming and Vyas, 1977). Experiment I shows that facilitation also occurs when a different display intervenes between two displays containing targets. Two further experiments show that detection of target letters among background letters is also facilitated if the same background letters recur on successive displays. Facilitation is greatest if background letters reappear in identical left-to-right spatial locations, but is also evident when the same background letters recur in different locations on successive displays. The results suggest modifications to models for the ways in which selective attention is continuously modulated by successive events during serial search.     

Processing a display even after you make a response to it. How perceptual errors can be corrected

We know that when people make responses which they did not intend they can discover this by monitoring kinaesthetic and visual feedback. It is less clear whether they can also correct perceptual errors which occur when they mistake one signal for another. It was argued that, if they can sometimes do this, extra errors which occur when discriminations become more difficult may be detected and corrected. Experiment I compared the ability of young fit subjects to detect errors made during easy and during difficult discriminations between tone signals. There was no evidence that any additional errors made to difficult discriminations were detected. Fast errors were detected, slower errors were not. The results were consistent with the idea that subjects can detect fast motor errors by monitoring feedback, but that they cannot detect perceptual mistakes.

In Experiment II subjects made easy and difficult line length discriminations. Displays lasted for 100 ms, 200 ms or 500 ms and were followed by random masks. In this case, fast errors were again corrected more frequently than slow errors but eight aspects of the data suggest that subjects could, and did, correct perceptual as well as motor mistakes and that they managed to do this by continuing to process a display after the moment at which they may have initiated an impulsive response to it. The data are interpreted in terms of a “Committee Decision” model for extended perceptual processing previously applied to other, similar data by Rabbitt and Rodgers (1977) and Rabbitt, Cumming and Vyas (1978).