Dot-probe paradigm

The dot-probe paradigm is a test used by cognitive psychologists to assess selective attention.

According to Eysenck, MacLeod & Mathews (1987) and Mathews (2004) the dot-probe task derives directly from research carried out by Christos Halkiopoulos in 1981 (see below the section on Who Invented the Dot Probe Paradigm). Halkiopoulos, later a doctoral student of Eysenck, carried out this research while he was a psychology undergraduate at UCL, under the supervision of professor N.F. Dixon. He introduced an attentional probe paradigm, which he initially used in the auditory modality to assess attentional biases to threatening auditory information, when threatening and non-threatening information was presented simultaneously to both ears in a dichotic listening task ([1][2][3]). Halkiopoulos demonstrated attentional biases by measuring reaction times to auditory probes following neutral and emotional words in the attended and the unattended channels. This method was subsequently used in the visual modality by MacLeod, Mathews and Tata (1986) in what came to be known as the dot probe paradigm. halkiopoulos's initial research is described by Eysenck, MacLeod and Mathews (1987) and, in some more technical detail, by Eysenck (1991). 


                                                        Who Invented the Dot Probe Paradigm?

A footnote of the original 1986 paper reads as follows: “Thanks are due to C. Halkiopoulos, whose unpublished doctoral research at Birkbeck College, London, motivated the development of the current paradigm.” (MacLeod, Mathews and Tata, 1986, p.15).

The use of the verb 'motivated' in this acknowledgement is ambiguous but Professor Mathews has subsequently clarified it further.

In 1990, he comments on the same paradigm as follows:

“In an initial unpublished experiment by a student of Michael Eysenck (C. Halkiopoulos), high trait anxious Ss were found to detect tones in a dichotic listening tape more rapidly if these followed a threatening word. Converting this to the visual modality, we found a similar effect in clinically anxious (GAD) Ss” (Mathews, 1990; p.459).

In 2004, Professor Mathews in an interview where he discusses his team's research and his collaboration with Eysenck, leaves no doubts as to who originated the paradigm:

"Then Michael Eysenck made contact, and we picked the idea for the dot probe method from his student, Christos Halkiopoulos. I certainly remember that being a really fun time" (Mathews in Borkovec, 2004, p.13).

The two relevant uses of Halkiopoulos's attentional probe paradigm, as discussed in consecutive paragraphs by Eysenck, MacLeod and Mathews (1987), are as follows:

                               Halkiopoulos's 1981 experiment (from Eysenck, MacLeod and Mathews, 1987; p.191)

“A student of the senior author (Christos Halkiopoulos) used a modified version of the dichotic listening task. Forty synchronized pairs of words were presented at a rate of one pair per second, and all of the words presented to one ear had to be shadowed, that is repeated back aloud. Half of the words presented on the shadowed or attended channel were emotional or threatening words (e.g., grave; fail), and the remainder were neutral (e.g., chairs; sale). All of the words presented on the unattended channel were neutral. A measure of the allocation of processing resources or attention was obtained by asking subjects to respond as rapidly as possible to occasional tones that could be presented to either ear immediately after a pair of words had been presented. A total of eight tones were presented, four on each channel; half of the tones in each channel followed a threatening word in the attended channel, and the remainder followed a neutral word in the attended channel. The Facilitation-Inhibition Scale (Ullman, 1962), which correlates very highly with measures of trait anxiety, was administered to 17 subjects, 10 of whom were classified as inhibitors and 7 as facilitators.

The probe reaction-time data were submitted to a three-factor split-plot analysis of variance, with facilitation-inhibition as the between-subjects factor, and probe channel (attended vs unattended) and attended word type (threat vs nonthreat) were the within-subjects factors. The key finding was the highly significant three-way interaction involving all of the experimental factors [F (1,15)=9.00, P<0.01]. More detailed examination of this interaction revealed that the interaction between probe channel and attended word type was significant for facilitators [F(1,6)=8.81, P,0.0025] and the same interaction with an opposite pattern was also significant for inhibitors [F(1,9)=3.36, P,0.05].”


                    MacLeod, Mathews and Tata's (1986) experiment (from Eysenck, MacLeod and Mathews, 1987; p.191)

“A rather similar paradigm was used by MacLeod, Mathews, and Tata (1986). Pairs of words were presented concurrently for 500ms, one word appearing towards the top of a screen monitor and the other towards the bottom. One some trials one of the words was a threat word (physical health or social threat) and the other word was neutral. The main task was to read aloud the top word of each pair, but sometimes a faint dot or probe replaced one of the displayed words, requiring a rapid response. Detection latency for the probe was regarded as a sensitive measure of visual attention, an assumption that has received empirical support (Navon & Margalit, 1983).The anxious group consisted of patients with a primary diagnosis of generalized anxiety and there was a group of normal controls. …The crucial finding in the analysis of the probe reaction-time data was a highly significant three-way interaction among anxiety groups, threat location, and probe location. The pattern of this interaction corresponded closely to that obtained by Halkiopoulos. …The similarity of the findings reported by C. Halkiopoulos (personal communication) and by MacLeod et al. (1986) is striking [.]”



IN many cases, the dot-probe paradigm is used to assess selective attention to threatening stimuli in individuals diagnosed with anxiety disorders. Biases have also been investigated in other disorders via this paradigm, including depression, post-traumatic stress disorder and chronic pain. Attention biases toward positive stimuli have been associated with a number of positive outcomes such as increased social engagement, increased prosocial behavior, decreased externalizing disorders, and decreased emotionally withdrawn behavior.[4]

Procedure and method

During the dot-probe task, participants are situated in front of a computer screen and asked to stare at a fixation cross on the center of the screen. Two stimuli, one of which is neutral and one of which is threatening, appear randomly on either side of the screen. The stimuli are presented for a predetermined length of time (most commonly 500ms), before a dot is presented in the location of one former stimulus. Participants are instructed to indicate the location of this dot as quickly as possible, either via keyboard or response box. Latency is measured automatically by the computer. The fixation cross appears again for several seconds and then the cycle is repeated. Quicker reaction time to the dot when it occurs in the previous location of a threatening stimulus is interpreted as vigilance to threat.

Clinical uses

Researchers have recently begun using a modified version of the dot-probe task to retrain the attentional bias. In this version, the probe replaces the neutral stimuli 100% of the time or the salient stimuli 100% of the time. Over the course of a number of trials the attentional bias for salient stimuli can be reduced (in the case of the 'replace-neutral' condition) or enhanced (in the case of the 'replace-salient' condition).[5] This method of retraining the attentional bias is called attentional retraining.

Some studies that use a dot-probe task
  • Halkiopoulos, C. (1981). Towards a psychodynamic cognitive psychology. Unpublished BSc dissertation manuscript, University College London, London, UK.
  • MacLeod, C., Mathews, A. M., & Tata, P. (1986). Attentional bias in emotional disorders. Journal of Abnormal Psychology, 95, 15-20.
  • Amin, Z., Constable, R.T., Canli, T. (2004). Attentional bias for valenced stimuli as a function of personality in the dot-probe task. Journal of Research in Personality, 38, 15-23.
  • Bradley, B.P. (1998). Attentional Bias for Threatening Facial Expressions in Anxiety: Manipulation of Stimulus Duration.
  • Mogg, K, & Bradley, B.P. (1999) Orienting of attention to threatening facial expressions presented under conditions of restricted awareness. Cognition and Emotion, 13, 713-740.
  • Mather, M., & Carstensen, L. L. (2003). Aging and attentional biases for emotional faces. Psychological Science, 14, 409-415. PDF
  • Schoth, D. E., & Liossi, C. (2010). "Attentional bias towards pictorial representations of pain in individuals with chronic headache". The Clinical Journal of Pain. 26 (3): 244–250. doi:10.1097/AJP.0b013e3181bed0f9. PMID 20173439.CS1 maint: multiple names: authors list (link)

Mathews, A. (1990). Why Worry: The Cognitive Function of Anxiety. Behaviour Research and Therapy, 28(6), 455-468).

  • Mathews, A., & MacLeod, C. (2002). "Induced processing biases have causal effects on anxiety". Cognition & Emotion. 16 (3): 331–354. CiteSeerX 10.1.1.329.4292. doi:10.1080/02699930143000518.CS1 maint: multiple names: authors list (link)
  • Eysenck, M., MacLeod, C. & Mathews, A. (1987). "Cognitive functioning and anxiety". Psychological Research. 39: 189–195. doi:10.1007/bf00308686.CS1 maint: multiple names: authors list (link)


References
  1. Halkiopoulos (1981)
  2. Eysenck, M., MacLeod, C. & Mathews, A. (1987). "Cognitive functioning and anxiety". Psychological Research. 39: 189–195. doi:10.1007/bf00308686.CS1 maint: multiple names: authors list (link)
  3. Mathews, 1990
  4. Troller-Renfree, S.; Martin McDermott, J.; Nelson, C.A.; Zeanah, C.H.; Fox, N.A. (2014). "The effects of early foster care intervention on attention biases in previously institutionalized children in Romania". Developmental Science. 18 (5): 713–722. doi:10.1111/desc.12261. PMC 4447605. PMID 25439678.
  5. Mathews, A., & MacLeod, C. (2002). Induced processing biases have causal effects on anxiety. Cognition & Emotion, 16(3), 331-354.

Borkovec, T.D. (2004). Andrew Mathews: a brief history of a clinical scientist. In Yiend, J. (Ed.), Cognition, Emotion and Psychopathology: Theoretical, Empirical and Clinical Directions. Cambridge University Press.

Eysenck, M. W> (1991)Trait anxiety and cognition. in C. D. Spielberger, I.G., Sarason, Z. Kulczar & J. Van Heck (Eds.), Stress and Emotion (Vol. 14). Hemisphere.

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