1、Experimental Psychology School of Psychology Zhao FanA Psychology Course in Central China Normal UniversityQQ: 1024-2410-81 Attention and Reaction TimeOrigin of RT research / The First RT Study: Personal equation (人差方程人差方程B-A=1.22s, B is Bessel, A is another visiting astronomer, Walbeck)：a systemati

2、c difference in RTs found among eighteenth-century astronomers.Mistakes/Incompetence?1796 Royal Observatory in Greenwich, England, one assistant was fired because his boss found that his crossing times (when a celestial body crossed a line marked inside telescope, expect to the precision of 1/10th s

3、; a nearby clock ticked every s; “eye and ear” method) were always (systematically) too great. They had assumed that all observers were consistent in their timing of the transits. The boss thought that the assistant made errors or did not grasp the right method during his observations.1820-21, Germa

4、n astronomer Bessel suspected that people might observe the crossing with slightly different RTs. Origin of RT research / The First RT Study: Bessel found the disagreement of crossing timing is common in all astronomers, even among the most experienced ones.Mistakes/Incompetence?In fact, he had not

5、really made errors at all!Individual difference (among people over which they have no control) rather than mistakes/incompetence! Personal equation is used to compensate individual difference in RTs.How the Astronomers responded to it?Compensation to Individual Difference in RT: These principles are

6、 universal: In response to this realization, astronomers became increasingly suspicious of the results of other astronomers and their own assistants, and began systematic programs to attempt to find ways to remove or lessen the effects. Compensation to Individual Difference in RT: These principles a

7、re universal: These included attempts at the automation of observations (appealing to the presumed objectivity of machines), training observers to try to avoid certain known errors (such as those caused by lack of sleep), developing machines which could allow multiple observers to make observations

8、at the same time, the taking of redundant data and using techniques such as the method of least squares to derive possible values from them, and trying to quantify the biases of individual workers so that they could be subtracted from the data.How the Astronomers responded to it?Compensation to Indi

9、vidual Difference in RT: These principles are universal: It became a major topic in experimental psychology as well, and was a major motivation for developing methods to deal with error in astronomy.Early RT Study: In an early RT experiment (1851), Helmholtz measured the speed of the nervous impulse

10、, showing how to implement experimental techniques on psychological topics. Stimulated blindfolded people on either the shoulder or the ankle and measured how fast they could react with their hand (by pushing a lever) in each case; around 50m/s, around 26m/s for frog nerve.Hermann Ludwig Ferdinand v

11、on Helmholtz (1821 1894), German physician and physicistThe sensory physiology of Helmholtz was the basis of the work of Wilhelm Wundt (1879 first psychology lab), a student of Helmholtz.Donders Subtractive method: 1868, Donders, a Dutch physiologist, realized he could use peoples reaction times to

12、calibrate the time required for various mental operations.Designed three RT tasks that are still called Donders A, B, and C reactions, Donders A RT: simple RTPerhaps providing a baseline of the cognitive operations.Donders B RT: choice RTA (Baseline Time) + Identification + (Response) SelectionDonde

13、rs C RT: discriminative RTTwo stimuli but only one is linked to a response.Figure 8.1.RT：doesnt mean executive time of performing a response; but refers to temporal delay from stimulus application on organism to distinct response;Donders Subtractive method: Figure 8.2C-A = Stimulus Identification Ti

14、me;B-C = Selection Time Donders Subtractive method: Subtractive method was initially used to measure time taken for a psychological process.Donders Subtractive method: Look in opposite way, since a psychological process always need time to develop, thus, it is possible to confirm existence of a psyc

15、hological process by subtracting two RTs.Subtractive method is an important technique used in cognitive psychology.Assumption of Pure Insertion: Cognitive Psychology tries to divide a complex process, such as attention, into a set of components parts or modules. One important criterion to identify t

16、hese component modules is separate modifiability, e.g. we can modify one component module without changing the others. In term of using RT, a corresponding concept is called Pure Insertion: A mental module can be added or deleted without altering the duration of other modules. Assumption of Pure Ins

17、ertion: In order to test PI, we need add another measurement to Donders ABC, Why? (separate modifiability) How about Response Force?Ulrich et. al.s first EXP (1999), Left or Right light presentation; Same Hand-Either Light Location in A; Different Hand-Different Light Location in B; Response-One Han

18、d, NoResponse-Another Hand in C. Integrated Force (Force Accumulation within a time window);Assumption of Pure Insertion: Consistent with PI since Force is kept same regardless of type of reaction. Confounding: 2 S 1 R?Force is still kept same. But RT: B=C! Confounding: Apparent Stimulus Intensity i

19、n C (where Ss can focus one but ignore another side)?RT: CA consistent with PI. But Force: CA inconsistent with PI!Assumption of Pure Insertion: Potential Confounding variables (Not a good design!): Two stimuli were mapped to the response in A! No simultaneous comparison of A, B, and C. Should use B

20、etween-S design if negative transfer is an issue! Possible confounding of apparent stimulus intensity in C (where Ss could focus one side while ignore the other). Figure 8.6-B vs.C with X/S in the fovea. Assumption of Pure Insertion:RT: BC consistent with PI.Force: B=C consistent with PI.Summary:EXP

21、 Design: Should use either a Within-S design (A, B, C together) or just a Between-S design!Taken together: Ponders model and PI may be correct (at least for A and B) but need further experiments to confirm.Why studies that measure RT should also record error rate?Errors tend to be higher when a task

22、 is completed quickly. Speed-Accuracy Trade-Off: Figure 8.7. Task: Name the digit! Theios (1973)s RT data and Pachella (1974)s CR data suggest:Theioss conclusion that stimulus probability had no effect on RT is wrong. Pathella suggested that in order to decrease the error rate to 2%, RT of 0.2 condi

23、tion need a increase of 100ms! Thus, RT and error rate must be jointly considered!Important EXP: Sternbergs memory-scanning taskSternberg (1966); Ss were told to remember a set of unique digits in short-term memory. Ss were then given a probe stimulus in the form of a digit from 0-9. The S then answ

24、ered as quickly as possible whether the probe was in (+) the previous set of digits or not (-). Important EXP: Sternbergs memory-scanning taskThe idea is that as the size (N) of the STM set increases the number of processes (that need to be completed before a decision can be made) increases as well.

25、 So if the S has 4 items in STM, then after encoding the probe the S will need to compare the probe to each of the 4 items in memory and then make a decision. If there were only 2 items in the initial set of digits then the number of processes would be reduced by 2. Four successive or serial stages

26、(a-Encoding probe; b-serial scan; c-decision; d-response organization).Important EXP: Sternbergs memory-scanning taskThe data found that for each additional item added to the set of digits that the subject had in STM about 40 ms were added to the response time of the subject. This finding supported

27、the idea that a subject did a serial exhaustive search (if so, same slops for + and -) through memory rather than a serial self-terminating search (if so, smaller slope for + relative to -). Important EXP: Sternbergs memory-scanning task RT(+) = 350 + 40N; RT(-) = 400 +40N; RT(-) RT(+)=50ms; N only

28、affects stage b! Response type (+ or -) only affects stage c! Quality of the probe only affects stage a! Probability of the response type (+ or -) only affects stage d!Important EXP: Sternbergs memory-scanning taskSternberg (1969) developed a much-improved method for dividing reaction time into succ

29、essive or serial stages (a-Encoding probe; b-serial scan; c-decision; d-response organization), called the additive factor method.Logic of additive approach：If two factors interact，then they affect on the same processing stage，if two factors have no interactions，they are independent，and play roles i

30、n different processing stages；Important EXP: Open Window ParadigmHamilton 1977 & Hockey 1981 Open Window Paradigm. This paradigm can direction measure time taken of each processing stage, and can specify some processing stage in a clear way.Paradigm used: stimuli on the display is like Four Lett

31、ers+4 ; Procedure: pressKey to elicit letter K, then report the conversion L-M-N-O, then PressKey to elicit letter EN after dealing with the last letter C, then report “O-I-R-G” together (for KENC) to guarantee successful memorization.Important EXP: Open Window ParadigmBased on RT data, 3 processing

32、 stages can be seen during letter conversion: encoding stage, from seeing the first letter by pressing a key to reporting orally，Ss try to encode the letter and find its location in alphabet table; (2) conversion stage, time used for predefined conversion; (3) storage stage, from the end of reportin

33、g to seeing next letter by pressing key, Ss put the converted results into memory.Thus get data of 12 RTs, after data analysis, can see the whole letter conversion process and different processing stages.Important EXP: Shepard and Metzlers mental rotation taskShepard and Metzler (1971) presented a p

34、air of three-dimensional shapes that were identical or mirror-image versions of one another. Reaction time to determine whether they were identical or not was a linear function of the angular difference between their orientation, whether in the picture plane or in depth. Same pair of 80 degIn the pi

35、cture planeSame pair of 80 degIn depthDifferent pair, can not be brought into congruence in any rotation!Important EXP: Shepard and Metzlers mental rotation taskThey concluded that the observers performed a constant-rate mental rotation to align the two objects so they could be compared.It is associ

36、ated with the rate of spatial processing and intelligence (Johnson 1990, Jones 1982, Hertzog 1991).Same pair of 80 degIn the picture planeSame pair of 80 degIn depthDifferent pair, can not be brought into congruence in any rotation!Important EXP: Shepard and Metzlers mental rotation taskDiscussion:

37、Experimental design:What kind of design？How many factors? How many levels in each factor? What is IV, DV? How many trials you plan to do together?What is the extraneous factors? Is there any control factors?What factors need to be counterbalanced?What other factors that you need to report in the exp

38、erimental report?What factors might affect RT?2 X 8 Within-S design; Repetition: 20 trials;Include External and Internal factors：External ones include：Stimulus Factors；Environment Factors；Device Factors;Stimulus Factors：(1)Modality to present stimulus：RT in touchRT in auditory Central-processing of Task 2 will wait. Central Capacity Sharing: Tombu & Joliceur, 2003, Figure 8.11; postulate a theoretical resource called capacity that is shared across tasks. Capacity Sharing - Lesser efficiency for each task.Central Capacity SharingCentral BottleneckHow can