Gary Marcus published a 1999 Science article on infant rule learning.

True: Marcus is an author (sole or co-author) of an article in the journal Science, published in 1999, on rule learning in infants (e.g., Marcus, Vijayan, Bandi Rao & Vishton, 'Rule learning by seven-month-old infants', Science 1999). Mostly true: such a Science article exists, but with a minor discrepancy, such as the year being off by one or it being a closely related publication type (e.g., a report rather than a full article). Mixed: not applicable to this single fact, beyond the minor slips covered above. Mostly false: Marcus published on infant rule learning that year, but in a different journal, or the Science paper is on a different topic. False: no 1999 Science publication by Marcus on infant rule learning exists in the journal's index.

Set before the research began.

1. E1 Rule Learning by Seven-Month-Old Infants Science (AAAS), reproduced as a JSTOR-derived PDF in the University of Amsterdam ILLC archive · 1 January 1999

   “Author(s): G. F. Marcus, S. Vijayan, S. Bandi Rao, P. M. Vishton”

2. E2 Rule Learning by Seven-Month-Old Infants Science (AAAS), reproduced as a JSTOR-derived PDF in the University of Amsterdam ILLC archive · 1 January 1999

   “Source: Science, New Series, Vol. 283, No. 5398 (Jan. 1, 1999), pp. 77-80”

3. E3 Rule Learning by Seven-Month-Old Infants Science (AAAS), reproduced as a JSTOR-derived PDF in the University of Amsterdam ILLC archive · 1 January 1999

   “A fundamental task of language acquisition is to extract abstract algebraic rules.”

The article's author line lists G. F. Marcus as a co-author of 'Rule Learning by Seven-Month-Old Infants' (E1). It was published in Science, Vol. 283, No. 5398, dated Jan. 1, 1999 (E2). Its abstract concerns the extraction of abstract algebraic rules in language acquisition, which is infant rule learning (E3). This meets the true criterion exactly.