Attention, Perception, & Psychophysics
2009, 71 (5), 985-987
News From the Field
PROBABILITY PERCEPTION Experiments on attention and psy- the likelihood of such movements. Of
chophysics often require observers course, in cases where precise fixation
Why We See Randomness
to maintain fixation to ensure that must be maintained, as when making
Correctly the results are due to covert atten- electrophysiological recordings, gaze
Hahn & Warren (2009). Perceptions of ran- tion or to effects at a specific reti- monitoring will be required. However,
domness: Why three heads are better than four.
Psychol Rev, 116, 454. nal locus. Unfortunately, the typical using fixation training can minimize
solutions for minimizing eye move- the amount of data lost to errant sac-
Kahneman and Tversky (1972, ments can be problematic. Eyetrack- cades. —S.P.V.
Cogn Psych 3:430) convincingly ers are costly (and underutilized if
demonstrated that people incorrectly only used to monitor gaze position), EARLY SPEECH PERCEPTION
perceive the randomness of events. and brief timing parameters are not
Given all possible results of tossing always feasible when studying cer- Separating the Wheat
a coin, the likelihood of observing a tain phenomena. From the Chaff
streak of four heads (HHHH) and a Enter a potential solution: Train Best et al. (2009). Development of phono-
specific nonstreak (e.g., HHHT) are observers to maintain f ixation. logical constancy: Toddlers’ perception of
the same. Most people incorrectly native- and Jamaican-accented words. Psychol
Guzman-Martinez et al. did exactly Sci, 20, 539.
judge the streak to be less likely. this by showing observers random dot
Hahn and Warren argue, however, displays. The display flickered, with As children begin to acquire a spo-
that given the experience that people all black pixels becoming white, and ken language, such as English, they
have of random events, this judgment vice versa. When observers main- must learn which differences in pro-
is not only reasonable, but correct! tained fixation, the display appeared nunciation matter, and which don’t,
Given one specific result of tossing to be uniformly gray because of per- in order to understand spoken words.
a coin a finite number of times, the ceptual averaging; if their eyes moved, Differences in dialects and accents, in
probability of observing a streak is they perceived instead a black-and- particular, can significantly change the
actually less than that of observing a white pattern. To train fixation, the way spoken words are produced, and
specific nonstreak. The probability of authors first had observers perform children must undercover what prop-
observing HHHH in a given set of 20