That is, even though Stimulus X and the outcome co-occurred during the compound AX learning phase, little learning of this regularity is observed.
Several theoretical accounts of blocking and overshadowing have been presented over the years e. This can account for blocking: the A-outcome association is learned early on, because the outcome is initially unexpected. As a result, very little is learned about the Stimulus X-outcome relation. Therefore, learning i. Importantly, cue competition effects are not observed under all conditions. For instance, overshadowing in conditioned lick suppression diminishes with extended training S.
Similarly, blocking also seems to be quite parameter dependent, as a recent experiment failure to find blocking in animals illustrates Maes et al.
As will be discussed in more detail in the General Discussion, there is not always clear agreement over which factors are important in determining the coming and going of cue competition effects cf. One issue that still remains unclear is whether cue competition can be found in incidental learning tasks, that is, tasks in which predictive cues were not task relevant targets.
Shanks, There are a few exceptions. Hendrickx and De Houwer described unpublished data with the correlational cueing paradigm J. Miller, , which is conceptually similar to the paradigm that we will adopt in the present work. In particular, participants responded to a central target letter, and flanking letters, which were predictive of the target response, served as blocking and blocked cues.
Importantly, however, the task was to respond to the target. Participants were not informed about the contingencies between the flankers and the targets, nor were they required to learn those contingencies.
Hence, the correlational cueing task can be described as an incidental learning task. One experiment hinted at a blocking effect, though overall response times were substantially faster in the blocking condition for unclear reasons, potentially eliminating the contingency effect due to a floor effect, rather than blocking per se as discussed in a thesis on the same data; Hendrickx, In follow-up studies, blocking was no longer observed. In some contextual cueing studies, Beesley and Shanks similarly failed to observe evidence for blocking in an incidental learning visual search context, even with some evidence of augmented learning of blocked cues.
Although these studies demonstrate that cue competition does not depend on the intentional expression of contingency knowledge, the learning itself was most likely intentional given that participants were asked to detect contingencies during the learning task.
Overshadowing studies are mixed. McLaren and colleagues observed impaired learning based on predictive colour cues when response sequences were predictable. Similarly, Endo and Takeda observed impaired learning based on distracter identities in a contextual cueing procedure when distracter configurations were redundantly predictive of the target location.
Thus, it seems clear that when there are redundant cues of targets, one cue dimension may be used preferentially. This is likely due to the procedures used, where, for instance, one cannot present colour cues without a sequence of prior responses or present distracters with identities but no locations. The main aim of our studies was to further explore cue competition in incidental learning tasks.
We did not have clear predictions about what we would find. On the one hand, the association formation models discussed above e. It is generally assumed that association formation processes operate independently of the intention to learn. Therefore, if cue competition effects arise as the result of these processes, and if all other boundary conditions are met, then those effects should also arise in incidental learning tasks.
This might be because Stimulus A is present. Hence, I do not know whether Stimulus X helps in any way. Such uncertainty can explain reduced learning about Stimulus X in the blocked context compared to when X on its own is paired with the outcome. During an incidental learning task, participants may be less likely to deliberately reason about the task in such a way, reducing or eliminating cue competition effects.
The words in the task are colour-unrelated neutral words. Most critically, each word is presented most often in one colour e. This produces high contingency trials, in which the word is presented in its most frequently paired colour e. Responses are faster and more accurate to high contingency trials relative to low contingency trials, indicating an influence of the contingency on performance.
As such, the task qualifies as an incidental learning task. Indeed, presence of the effect does not depend on contingency awareness. Colour-word contingency effects perhaps poorly named have been observed with dimensions other than words and colours. Levin and Tzelgov observed quite robust contingency effects with distracting shapes. In fact, the contingency effect for shapes during colour identification was even a bit larger than the effect for words.
These two dimensions are also useful in the sense that one can have: a word-only trials coloured word, no shape , b shape-only trials coloured shape, no word , and c compound stimulus trials coloured word and shape. In Experiment 1, we tested for overshadowing in the colour-word contingency learning paradigm. The general trial procedure and example compound stimuli are illustrated in Figure 1.
In particular, compound cues can be presented by printing a word inside a shape, both coloured in the same hue. In the critical compound-cue condition, participants are consistently presented with both a word and a shape in a colour during a training phase. Each word-shape compound is presented most often in one colour e. Example relative stimulus frequencies by phase are presented in Table 1.
General trial procedure top and example compound stimuli bottom. After a fixation cross and blank screen, a word-shape compound or just a word or shape is presented briefly in black, then changed to one of the target colours. See the online version of the article for a coloured figure. Note: Example mappings only. Which words, shapes, or word-shape combinations went most frequently with which colours was counterbalanced across participants. High contingency items are indicated in bold.
Using this procedure, we can test for contingency transfer effects for both words and shapes to see whether either stimulus dimension overshadows the other. If overshadowing proves to be less than complete, this would indicate that transfer from compound-cue training to one or both of the elements of the compound is possible during incidental learning in the colour-word contingency learning task.
As control conditions, a words-only group of participants were trained only with words in colours i. If some degree of overshadowing perhaps not complete is present, then we should expect contingency effects in the test phase to be smaller in the compound-cue group relative to the control groups. We also tested for subjective and objective awareness of the contingency manipulation to determine whether any observed overshadowing was related to awareness.
More specifically, we examined whether learning effects for the overshadowed or blocked cue i. For instance, it may be that A only blocks X if participants have explicitly noticed the contingencies in the task. If so, the magnitude of the contingency effect at test for X should be inversely related to awareness.
Note, however, that the issue of whether cue competition effects are influenced by contingency awareness is different from and only indirectly related to the issue of whether learning is incidental. For instance, contingency awareness can arise even if learning is incidental. We also registered contingency awareness as an additional dependent variable that might well provide evidence for overshadowing and blocking. It is again important to stress that our task qualifies as an incidental learning procedure.
Both words and shapes are, of course, predictive of the target response, but task irrelevant i. Thus, any learning of the word-response or shape-response contingencies is most likely incidental rather than the deliberate goal of the task.
The study itself was hosted on millisecond. We aimed for at least 40 participants per condition. With no directly comparable prior studies, this number was determined subjectively, but fixed a priori. There is some randomness in study completions after participant number assignment on millisecond. An additional 12 submissions were deleted due to excessive errors see Data Analysis. The experiment was programmed in Inquisit 5 and designed to work on a PC with an enforced canvas aspect ratio.
Participants responded by pressing the J, K, and L keys to blue, red, and green stimuli, respectively. During the main task, either a word, shape, or word inside a shape was presented. The shapes were When the shape and word were both presented, the word fit inside the shape outline.
Cues preceding outcomes is also typical of many cue competition studies in both animals and humans e. Participants were randomly assigned to see only coloured words, only coloured shapes, or both a coloured word and shape both same colour during the training phase. When words were presented inside shapes, the same word always corresponded to the same shape, although which word was presented with which shape was randomly determined on a participant-by-participant basis.
In the final test phase, all participants saw both trials with coloured words only and trials with coloured shapes only. The contingencies were removed in the test phase, such that each word and shape was presented equally often in all colours.
Thus, for the words-only and shapes-only groups, we expected a contingency effect during test only for the trained dimension words and shapes, respectively and no effect for the untrained dimension i. The compound-cue condition is the most interesting, in which we test to see a whether a test contingency effect is observed for both word and shape test trials, and b whether any such contingency effect is reduced relative to the two control groups.
There were 90 practice trials, selected randomly, followed by two training blocks shapes-only, words-only, or compound-cue of trials each, and a test block of 90 trials. There were self-paced pauses between blocks. All stimuli were presented on a white ,, background.
Next, the stimulus was presented in black for ms before changing to one of the target colours. Responses could not be recorded prior to the colour change. Following a correct response, the next trial immediately began.
After the main procedure, participants were asked for their subjective and objective contingency awareness. For the former, they were asked:. This experiment was divided into three parts, starting with a practice phase coloured rectangles and ending with a test phase coloured words or coloured shapes. This was followed by three randomly-ordered trials, each with one of the initially trained stimuli in black.
Data analysis. Both mean correct response times and error rates were assessed. Trials on which participants failed to respond were eliminated from analyses. We supplement each key Null Hypothesis Significance Test NHST with Bayesian analyses in this and the following experiment, particularly relevant for non-significant effects.
In all cases, Bayesian tests were computed with a half normal distribution with a mean of zero and the effect in the control condition as the prior standard deviation with an online Bayes calculator from Dienes, BF 10 indicates evidence in favour of an effect and BF 01 indicates evidence in favour of a null.
We report the Bayes factor for the direction that the data favours e. Training phase. Control groups test. The response time data are presented in the left panel of Figure 2. First, we analyzed the two control groups to assure that robust contingency effects were observed during test for both words and shapes. The pattern was similar for the shapes-only group. Experiment 1 response time left and percentage error right contingency effects low — high contingency as a function of group and phase, with standard error bars.
Compound-cue group test. Next, we turn to the compound-cue group. For errors, the contingency effect was non-significant for words high: 6. Cross-group comparisons. Robust contingency effects were observed in both training and test albeit only for response times at test in the compound-cue condition for both the words and the shapes. Thus, complete overshadowing was decidedly not observed. However, we next examined to what extent partial overshadowing might have been observed by directly comparing the compound-cue group to the controls using a series of ANOVAs comparing the contingency effect high vs.
For the word test trials, we used the words-only group as controls; and for the shape test trials, we used the shapes-only group as controls. Thus, the error results, unlike response times, do not provide clear evidence that there was no overshadowing at all. It is also worth noting that a half-normal test is biased against inferences in favour of the null i. Contingency awareness. Correlations with the response time training and test effects are presented in Table 2.
As can be observed, there was some albeit weak and inconsistent evidence for larger effects with increased contingency awareness. In the absence of an overall overshadowing effect, no further analyses of the awareness data were conducted. In Experiment 1, no clear evidence for overshadowing was observed. Overshadowing takes place when a certain stimulus is not noticed by the animal because there is a more salient more evident stimulus around. Let's try to make an example.
If you are training using luring, rest assured that dogs will pay more attention to a treat used as a lure than a verbal command if the lure is not faded quickly. In this case, the most salient stimulus the lure overshadows the other stimulus the verbal command. Another example: If you are training your dog to sit and you say "sit" while you move your head downwards, guess what will likely happen?
Your head movement will overshadow your verbal command. Dogs are masters in looking at our body language, so our movements are much more salient than our voices. What will happen then?
You may end up with a dog that will not sit if you just say "sit" and fail to move your head downwards, but will sit promptly sit if you do move your head, even without saying "sit. If you are not into dog training but into human psychology or you failed to grasp the lure example, here is another example: a man is admiring a beautiful woman walking by the street as he is driving the car.
Yet the red stop sign is more salient, so he pays attention to it and stops looking at the pretty woman to watch for passing cars. In this case, the red stop sign has overshadowed the pretty lady and thankfully so! In blocking, a stimulus becomes irrelevant if it is presented together with an already familiar stimulus. For instance, if you are training your dog German commands and say "down" and "platz," the dog will likely not rely on "platz" because the familiar word "down" provides enough information, plus it has a history of reinforcement, so who cares about "platz.
If you are looking for a human example, here is one to make the concept clearer. If you have always stopped at a red stop sign, the day you find an intersection with both a red and a black stop sign, you will likely attend more to the red sign because it provides more information to you as it has a history of grabbing your attention. In this case, the red stop signs are blocking the black ones from having an effect on you.
As seen, both blocking and overshadowing have an effect on the outcome of dog training. While you may not need to understand these concepts to train your dog, they do come handy if you are wondering why your dog may not be listening to you and you need to do some troubleshooting. What is higher order conditioning in psychology? What is conditioned suppression? What is Latent inhibition in psychology? What is a compound stimulus?
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