the effect of a coloured letter in a word or non word on the reaction time of recognition processes.

University Degree Medicine and Dentistry

Abstract

This study examined the effect of a coloured letter in a word or non word on the reaction time of recognition processes. . Six hundred and twenty six participants (292 M, 334 F, M = 27.97 years, SD = 12.07 years) were asked to read a set of lists and name the ink colours which the words were printed in. In this case, two level of stimuli were used; namely the word or non-word. They were then timed on their reaction time when processing the colour of the letter positioned in a word and in a non word. The hypothesis stated that the position of the coloured letter interferes with the reaction time in the word recognition process. Not only this, the position of the colored word will also affect the reaction time. Finally, it was concluded that the position of the coloured letter does affect the colour naming task.

Introduction

Humans have many behaviours that are automatic like sensory reactions. Learned behaviours like reading are also said to be automatic where a stimuli elicits the behaviour in the absence of intention. The analyses of single words of semantic and lexical are uncontrollable.

The “Stroop effect” occurred when the identification of the colour of an incongruent word is much slower than the identification of a congruent word (Besner, Stolz, & Jones, 1997). J.R Stroop was the man who introduced the “Stroop task” in 1935. He published an article on interference and attention and his Stroop task had kept many psychologists interested in the functions of cognition and processes of attention ( MacLeod, 1991). In an experiment conducted by Stroop (1935), a number of variations of two main tests have been administered. The tests were known as RCN, "Reading Color Names", where participants were asked to repeat the written meaning of words with different coloured letterings, and NCW, known as "Naming Colored Words", where participants were asked to name the color of each printed word (Stroop, 1935). Stroop had discovered that participants relatively took a longer time to complete the NCW task even though they might have practice prior to the task. This is due to the fact that it is caused by automatization of reading whereby the mind had already automatically determines the semantic meaning of the word and thus must override the first impression with the identification of the color of the word, a process which is not automatized.

According to Besner et al. (1997), it was found out that the standard Stroop effect would either be eliminated or reduced in a single-coloured-letter condition. The same goes for cognition, in order to identify that the colour of a single letter is adverse to word processing to a semantic level, the significance of the Stroop effect should be smaller when all the letters are coloured. Therefore, the participants had to identify the colour from a string of words under the condition that all words were coloured incongruently and congruently, and also incongruent and congruent single letters. The participants were also asked to press keys that represent each colour naturally. Besner’s Stroop experiment had showed that whenever a single coloured letter was compared with whole coloured word, there was indeed a difference (Besner et al., 1997). Therefore, one can conclude that by controlling the stimulus, automaticity can be eliminated.

Besner also did another experiment to improve the study of automatic reading hypothesis with context to the Stroop task. It was predicted that if the congruent trials was replaced with non word controls, the semantic processing by the Stroop effect would have a bigger result difference between the single letter and whole word. The results itself had proved that the prediction is true and that Besner argues that automaticity was not the cause for the Stroop effect.

Danziger, Esteves and Mari-Beffa (2002) had researched on the effects of single letter colouring on word reading task. They wanted ...

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Danziger, Esteves and Mari-Beffa (2002) had researched on the effects of single letter colouring on word reading task. They wanted to find out whether word reading in the Stroop effect is automatic. The results of this study support the fact that single letter colouring in the Stroop task does causes Stroop interference.

However, the experiment done by Marmurek (2003) contradicted with the findings by Danziger et al. He has investigated the limitation of unintended processing of colour word whereby a single coloured letter in word would reduce interference in vocal responses. His experiment was aimed to eliminate the colour word interference by only colouring a single letter to control the colour naming task. The participants were told to name the colour of the letters by speaking into a microphone and another group of participants pressed keys on the response box. Results had showed that there were high levels of interference in the vocal response participants groups and this experiment did not agree with the findings of other experiments. This experiment was consistent with the automaticity theory and having a single colour letter does not eliminate vocal response.

Findings had shown that the position of coloured letters in a word affected the Stroop task and that interference caused by the single lettered colour was affected by the position of the letters in the word.

On the other hand, Cohen, Dunbar and McClelland (1990) had proposed an alternative connectionist explanation of the Stroop effect, whereby it does not differentiate between automatic and controlled processing. Instead, they projected that automaticity is a continuum, and that the level of Stroop interference depends on the relative degree of learning of the respective tasks, and not on the processing speed.

Raz, Kirsch, Pollard and Nitkin-Kaner (2006) had noticed that Stroop effect could be reduced or even eliminated by hypnotizing participants and telling them that the words were in a foreign language so they could focus fully just on colour alone. With this, they did a research and it shown that hypnosis is only effective when the person being hypnotized is already susceptible to hypnosis. Therefore in order for hypnosis to work, the person being hypnotized must be highly suggestible.

With this, an experiment was done on 25 highly suggestible individuals who were divided into two groups. Each group practiced the Stroop task for a few minutes: a word was flashed on the screen, and participants had to press a key on the computer that corresponds to the color that was displayed in. One group was being hypnotized, but the other was not. Whether or not the participants were hypnotized, all showed a diminished Stroop Effect the words were suggested to be gibberish. There was no significant difference in the results between hypnotized and non-hypnotized participants.

As the Stroop effect was not completely eliminated in this task, Raz argues on the basis that this experiment demonstrates that reading is not entirely involuntary. It is only an example that non hypnotized individuals can voluntarily reduce the tendency to automatically read the word they are looking at.

Finally, the present findings report a new manual task which almost completely eliminates the traditional Stroop interference and produces strong color-based interference when the task is to identify the words. The task is to point to a color by moving a mouse cursor to the color that corresponding to the desired response.

The present experiment showed that Stroop interference in responding to the sensory color of a conflicting color word can be eliminated. Participants were required to respond to the color that the target word was printed in, ignoring the word itself. However, in reverse Stroop condition, participants were to respond to the color named by the word, ignoring its incongruent physical color. In both cases the response was to move a mouse cursor to the color on the computer screen. In a simpler form, it mean that pointing to a matching color can be easily accomplished. However, pointing to a named color would require either categorical identification of the surrounding color patches or translation of the word into a visual code.

Method

Participants

The participants were a sample of 626 members of the public (M = 27.97 years, SD = 12.07 years). The sample consisted of 30 males (M = 27.53 years, SD = 11.75 years) and 30 females (M = 28.37 years, SD = 12.35 years). The participants had to be between 18 to 60 years old, English as their first language, able to read and understand English words, no descriptive restrictions and no colour blindness so that they could differentiate colours.

Design

This experiment is a 2 X 4 repeated measured design. The participants had to finish the experiment in order to be able to record differences in the ability of doing the Stroop task, the independent variable in the experiment would be the type of stimulus (colour names, non words) and the type of colour manipulation (first letter, middle letter, last letter and whole word) The dependent variable would be the reaction time taken to name to ink colour of the stimuli in each list in seconds.

Materials

Materials consisted on plain white A4 size papers, coloured pens in terms of red, green, blue and black and lastly a stopwatch to record the reaction time of the participants in the experiment. There are a total of eight experimental lists and on each list, there are 36 stimuli, in capital letters and printed in the centre of each column. The colour names are printed randomly 12 times in random colour, 6 times in one in colour and another 6 times in other ink incongruent ink colour.

The non words are those that were all-letter different to colour names and were being matched for their word length and ink colour. For example, RED was matched with PON, BLUE with DIRM and GREEN with STOAP.

Procedure

Each participant was tested individually with non distractions in order to minimize any interference that might affect the results. Participants each received a paper with nine stimuli lists stated on it. However, prior to this, they need to do a set of practice test where results were not recorded. After which, participants were then asked to read all the lists and name the ink colours from the word and read from column by column, from left to right in order to counterbalance for practice effect. All results were timed using a stopwatch and recorded in a data recording sheet.

Results

Results were processed by SPSS version 14.0. A two tailed paired sample t- test showed that the Stroop interference is at its highest when the whole word is coloured. The Stroop interference is at its lowest when the middle letter of a non word is coloured.

Figure 1 shows the mean reaction time (in seconds) for word and non-word across the four colour conditions (whole word, first letter, middle letter and last letter).

Figure 1 Mean reaction time (s) in naming the ink colour in each list

With reference to Appendix C (Paired-samples t-test), the results shown that there were statistical differences in the mean reaction time of participants paired-samples t-test for the whole-word-coloured condition, t(625) = 29.965, p < 0.001.

It was also shown that that there were statistical differences in the mean reaction time of participants for the first-letter-coloured condition, t(625) = 24.227, p < 0.001.

There were statistical differences in the mean reaction time of participants for the middle-letter-coloured condition, t(625) = 18.7, p < 0.001.

There were statistical differences in the mean reaction time of participants for the last-letter-coloured condition, t(265) = 14.652, p < 0.001.

Discussion

The results of this study supported the hypothesis that the positions of the colour letter in words do produce a different effect. The whole letter words produce more Stroop interference than the rest of the conditions.

The results of this experiment are consistent with the results of Besner et al., and Danziger et al. (2002). Though this study was done vocally which differ from Besner, however the results are consistent with Besner’s experiment because it supported the fact that automatcity might not be the basis of Stroop effect. In Danziger’s experiment, single coloured letters in the Stroop task produces Stroop interference in a position – sensitive nammer. It was found that with the whole word and last letter being coloured, interference was the greatest.

In conclusion, this study examined the interference of the different positions of coloured letter words and the results have shown that the position of the coloured letter do affect the results and have significant interference levels.

References

Besner, D., J.A., & Boutilier, C. (1997). The Stroop effect and the Myth of Automaticity. Psychonomic Bulletin & Review, 4, 221-225.

Cohen, J.D., Dunbar, K., and McClelland, J.L. (1990). On the Control of automatic processes: A parallel distributed processing account of the Stroop effect. Psychological Review, 97, pp. 332-361.

Danziger, S., Estevez, A.F., & Mari-Beffa, P. (2002). Stroop interference effects in partially coloured Stroop words. Psychonomic Bulletin & Review, 9(3), 536-541.

MacLeod, C.M. (1991). Half a century of research on the Stroop effect: An integrative review. Psychological Bulletin, 109, 163-203.

Marmurek, H.C. (2003). Colouring only a single letter does not eliminate colour-word interference in a vocal response Stroop task: automaticity revealed. Journal of General Psychology, 130(2), 207-224.

Raz, A., Kirsch, I., Pollard, J., & Nitkin-Kaner, Y. (2006). Suggestion reduces the Stroop Effect. Psychological Science, 17(2), 91-95.

Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643-662.