Aging and Visual Counting

Abstract

BackgroundMuch previous work on how normal aging affects visual enumeration has been focused on the response time required to enumerate, with unlimited stimulus duration. There is a fundamental question, not yet addressed, of how many visual items the aging visual system can enumerate in a “single glance”, without the confounding influence of eye movements.Methodology/Principal FindingsWe recruited 104 observers with normal vision across the age span (age 21–85). They were briefly (200 ms) presented with a number of well- separated black dots against a gray background on a monitor screen, and were asked to judge the number of dots. By limiting the stimulus presentation time, we can determine the maximum number of visual items an observer can correctly enumerate at a criterion level of performance (counting threshold, defined as the number of visual items at which ≈63% correct rate on a psychometric curve), without confounding by eye movements. Our findings reveal a 30% decrease in the mean counting threshold of the oldest group (age 61–85: ∼5 dots) when compared with the youngest groups (age 21–40: 7 dots). Surprisingly, despite decreased counting threshold, on average counting accuracy function (defined as the mean number of dots reported for each number tested) is largely unaffected by age, reflecting that the threshold loss can be primarily attributed to increased random errors. We further expanded this interesting finding to show that both young and old adults tend to over-count small numbers, but older observers over-count more.Conclusion/SignificanceHere we show that age reduces the ability to correctly enumerate in a glance, but the accuracy (veridicality), on average, remains unchanged with advancing age. Control experiments indicate that the degraded performance cannot be explained by optical, retinal or other perceptual factors, but is cortical in origin.

Aging and the number sense: preserved basic non-symbolic numerical processing and enhanced basic symbolic processing

“…Studies in the field of numerical cognition and aging have mostly investigated high-level mathematical skills, such as counting, arithmetic problem solving, and strategies for quantification (e.g., Duverne and Lemaire, 2004 ; El Yagoubi et al, 2005 ; Gandini et al, 2008 ). More recently, a handful of studies have investigated more foundational skills, such as non-symbolic numerosity discrimination ( Li et al, 2010 ; Dormal et al, 2012 ; Halberda et al, 2012 ; Cappelletti et al, 2014 ). However, results are contradictory, and therefore no clear conclusion can yet be drawn on the effect of aging on these basic numerical skills (see below).…”

“…More recently, some authors have begun to study non-symbolic numerosity processing in aging using brief stimulus presentation times. In Li et al’s (2010) study, older and younger participants were submitted to an estimation task on a small range (1–9), in which target numerosities were presented for 200 ms. The authors found that aging appears to be associated with poorer performance in small-quantity estimation, with older adults presenting slower reaction times (RTs) and greater response variability than the younger adults.…”

Using Potential Performance Theory to Analyze Systematic and Random Factors in Enumeration Tasks

“…Additionally, researchers investigating nonverbal counting have found that random noise tends to increase as a function of the number of items presented; more items typically leads to more noise (Cordes et al, 2001;Li et al, 2010). Additionally, researchers investigating nonverbal counting have found that random noise tends to increase as a function of the number of items presented; more items typically leads to more noise (Cordes et al, 2001;Li et al, 2010).…”

“…In past literature, there have been two prominent paradigms for studying enumeration processes (Beckwith & Restle, 1966): accuracy (Cordes et al, 2001;Li et al, 2010) and RT (Trick & Enns, 1997;Trick & Pylyshyn, 1993, 1994. The accuracy paradigm involves displaying a set of items for a limited amount of time and making a judgment about how many items were present.…”

“…A number of researchers have found that when people are engaged in nonverbal counting, the amount of noise in their approximations increases as a function of the actual number of items present (Cordes et al, 2001;Li et al, 2010;Logie & Baddeley, 1987). This means that the decrement in performance as set size increases may not result entirely from nonrandom processes.…”